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Thrips Show Promise in Controlling the Invasive Brazilian Peppertree in Florida

USDA Agricultural Research Service sent this bulletin at 10/12/2022 09:27 AM EDT

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ServiceBrazilian peppertree thrips larvae and adults feed on a Brazilian peppertreeBrazilian peppertree thrips larvae and adults feed on a Brazilian peppertree. (Photo by Dale Halbritter)Thrips Show Promise in Controlling the Invasive Brazilian Peppertree in FloridaFor media inquiries contact: Jessica Ryan, (301) 892-0085October 12, 2022Brazilian peppertree thrips (Pseudophilothrips ichini) showed promise as biological control agents for invasive Brazilian peppertree populations in Florida according to a recent study published in the Florida Entomologist.Thrips are common insect pests on horticultural plants, but specialized Brazilian peppertree thrips from South America feed exclusively on the Brazilian peppertree’s leaves and stem tips. Their feeding results in reducing the peppertree’s growth rate, plant height, number of leaves, and green stems as well as fruit and flower production.Scientists from the United States Department of Agriculture’s Agricultural Research Service (ARS) collaborated with University of Florida and Florida Department of Food and Consumer Services researchers to mass produce and release thrips throughout 567 sites in Florida between May 2019 and December 2021.The study results show that these thrips persisted in 60 percent of the survey sites for at least one generation as indicated by the recovery of adult thrips at least 60 days after their release. “This is a significant finding, because it indicates the thrips have a self-sustaining population at up to 60 percent,” said Gregory Wheeler, research entomologist at the ARS Invasive Plant Research Laboratory in Fort Lauderdale, Florida.Native to South America, the Brazilian peppertree is a woody and evergreen shrub known for its bright red berries and green foliage. This invasive species grows in dense thickets in invaded ranges and crowds native vegetation. Its fruit is toxic when consumed by wildlife, and many people have allergic reactions to its pollen and sap. In the U.S., the Brazilian peppertree has made its way to California, Florida, Hawaii, and Texas. In Florida alone, the Brazilian peppertree tree has colonized most of the state’s peninsula and covers more than 700,000 acres of land.Use of biological control agents can be a solution for land managers seeking to control invasive populations, according to Wheeler.”Biological control agents like thrips can be a cost-effective and environmentally friendly means of pest control that can be a part of an integrated approach that includes a number of different tactics,” said Wheeler.Thrips are the first biological control agent for this invasive species released in Florida. Researchers will continue field releases and assessments to determine thrips’ effectiveness.The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.Interested in reading more about ARS research? Visit our news archiveU.S. DEPARTMENT OF AGRICULTURE
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Fruit and vegetable crops in the Willamette Valley have been affected

USDA ARSWFP-ARS-BMSB.jpg

One promising biological approach is the samurai wasp (Trissolcus japonicus),

The brown marmorated stink bug has increased this year.

Fruit and vegetable crops in the Willamette Valley have been affected.

Kym Pokorny | Nov 11, 2022

Jan 18, 2023 to Jan 20, 2023

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The amount of invasive brown marmorated stink bugs in 2022 tops anything seen in Oregon for at least five years and poses a serious threat to Oregon crops and garden plants, according to Oregon State University Extension Service’s orchard crop specialist.

Nik Wiman, an associate professor in the College of Agricultural Sciences, said fruit and vegetable crops in the Willamette Valley have been affected.

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“It’s unusual for brown marmorated stink bugs to feed on fruit and vegetable crops,” he said. “There has been a lot of damaging populations of BMSB in hazelnuts orchards. Growers use preventative measures so we’re surprised we’ve seen so many.”

It’s unclear why the population exploded this year, Wiman said. Like other insects, the population of the shield-shaped brown marmorated stink bug (BMSB) varies from year to year depending on climatic factors. The extremely wet spring most likely contributed to it, but the increase could also be attributed to a natural cycle.

Native to Asia, BMSB was introduced on the U.S. East Coast in the late 1990s – probably by ship – and has spread to almost every state in the country, including Oregon in 2004. The insect feeds on at least 170 plants, particularly vegetables, pears, apples and hazelnuts, but also ornamentals. Its name describes the odor they emit when they’re crushed.

Oregon’s hazelnut industry, valued at $132 million in 2020, is one of the state’s crops hardest hit by the invasive bug, according to the Oregon Department of Agriculture. The state’s problem echoes the situation in Turkey – the world’s leader in hazelnut production – as well as Italy and the country of Georgia, said Wiman, who researches alternative practices for controlling BMSB, including biological control, habitat manipulation, trap crops and barriers.

Samurai wasp

One promising biological approach is the samurai wasp (Trissolcus japonicus), an insect native to areas of Asia where it keeps the indigenous BMSB population under control. Scientists have discovered the wasp in the United States and Oregon, where it was initially distributed across the state by Wiman and a team of scientists at OSU and elsewhere.  The Oregon Department of Agriculture is now leading the effort.

The parasitic wasp hunts for the egg masses of the stink bug and lays an egg inside each egg in the mass. The wasp develops inside the egg, effectively killing the stink bug, and then chews its way out. OSU Extension has a short publication on the wasp and its effect on the stink bug.

In addition to agricultural crops, the stink bug shows up in homes in autumn when they are looking for a warm, dry place for winter.

“We’ve done analysis of reports we get from people,” Wiman said. “We’ve looked at timing and by far and away we get the most BMSB reports in the fall. Adults are at peak and are trying to get into houses. Warm fall weather gives more opportunity to get into buildings. They can be very annoying when they are coming into homes, and they may fly around inside your house all winter. Then they come out in spring.”

Wiman advises homeowners to seal all cracks where the stink bug can enter and vacuum up inside infestations. On outdoor buildings, washing them off with a strong shot of water will keep some at bay. If they come back, spray them again.

Farmers and homeowners can serve a key role in samurai wasp research by collecting possible brown marmorated stink bug egg masses and reporting them.

[Kym Pokorny is a communication specialist at OSU.]

Source: Oregon State University

TAGS: CROPS

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NZ: Stink bugs at the border

As well as fruit flies, we are currently in the high-risk season for Brown Marmorated Stink Bug (BMSB). The season started in September and to date there have been two BMSB finds, compared to six for the same period last season. Both finds were at the border, by Quarantine Officers at Auckland Airport.

One of the finds was at a search bench where passengers from multiple fights from the USA were being processed; and the other was on an aircraft which had just arrived from South Korea.

More detail can be read in the latest KVH risk update for BMSB.

The risk period for BMSB stretches throughout the summer so remember to be on the lookout and report anything unusual. Information and videos about the risks this bug poses are available on the KVH website.

Publication date: Thu 10 Nov 2022

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First plant disease detection found in California; quarantine in place

Steve Angeles | TFC News California

Posted at Oct 27 2022 12:14 PM

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HLB on young tree

In Southern California, state agriculture officials are expanding a citrus plant quarantine in Los Angeles county after the citrus disease Huanglongbing (HLB) was detected in Pomona. 

Asian citrus psyllid

The plant disease is not harmful to people or animals but can greatly affect citrus plants. HLB is spread from plant to plant by the Asian citrus psyllid. Once a tree is infected it cannot be cured. 

ACP

According to the Citrus Pest & Disease program’s press release, a citrus plant quarantine is in place throughout portions of Los Angeles, Orange, Riverside, San Bernardino and San Diego counties. To further limit the spread of the pest that can carry HLB, there are additional quarantines in place that make it illegal to bring citrus fruit or plant material into California from other states or countries. 

The new quarantine map can be found at https://www.cdfa.ca.gov/citrus/pests_diseases/hlb/regulation.html.

Yellowing leaves

All citrus trees including, lemons, oranges, and limes can be affected by HLB.

While an outbreak of HLB could impact local citrus industries, backyard gardeners also need to be cautious. 

An estimated 60% of California homeowners own citrus trees, and a popular one among Filipino homes, is calamansi. 

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Read More:  Huanglongbing   HLB   Asian Citrus Psyllid   ACP   plant disease   quarantine   TFC News  

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South African pest poses serious risk to EU citrus producers, MEPs warn

By Natasha Foote | EURACTIV.com

 Oct 25, 2022 (updated:  Oct 26, 2022)

The European Commission was quick to reassure MEPs that they are “taking action to protect the farming community”. [SHUTTERSTOCK]

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EU producers cannot afford any confusion or loosening of controls on imports of citrus fruits from South Africa, MEPs have warned, stressing the spread of pests could imperil the sector, but the Commission insists its measures are sufficient.

Farming stakeholders are concerned over the spread of the false codling moth, a pest native to sub-Saharan Africa that feeds on fruits including oranges and grapefruits.

“If we have these pests, our farmers are not going to be able to fight them off or defend themselves. They will lose their crops only because we were not able to implement and enforce the regulation that is mandatory,” Spanish socialist MEP Clara Aguilera warned during a meeting of the European Parliament’s agriculture committee on Monday (24 October).

To stem the spread of the insect, the EU introduced new measures back in July that require South African farmers to apply extreme cold treatment to all Europe-bound oranges and keep the fruits at temperatures of two degrees Celsius (35 degrees Fahrenheit) or lower for 25 days.

However, South Africa, the world’s second-largest exporter of fresh citrus after Spain, filed a complaint with the World Trade Organisation (WTO) back in July, arguing that the EU requirements were “not based on science”, more restrictive than necessary and “discriminatory”.

Meanwhile, the subsequent confusion over the new import rules saw millions of boxes of oranges left to spoil in containers after being stranded at European ports back in August. 

Tonnes of fruit stranded in EU, South Africa battle of oranges

Millions of boxes of oranges are spoiling in containers stranded at European ports as South Africa and the European Union lock horns in a dispute over import rules, citrus growers have said.

Slamming the European Commission’s efforts to contain the spread of the pest so far, the MEP questioned why South Africa was allowed to “do as they please”.

“[The Commission] said that there are requirements that we have to comply with. That’s not the problem. The problem is that there isn’t compliance,” she explained, arguing that the measures taken so far are insufficient. 

“It’s not true that the Commission is trying to protect our farmers. If that were the case, these containers would have been sent directly back to their country,” she added.

For its part, the Commission was quick to reassure MEPs that they take plant and animal health “very seriously” and are “taking action to protect the farming community”.

“We are not afraid of taking strong measures to protect agriculture in the EU,” a representative from the Commission’s DG Sante said in response to the concerns. 

Meanwhile, the representative was quick to dispel rumours that the EU executive had struck a deal with South Africa to go easy on the restrictions. 

“The Commission did not make any agreement with South Africa on the cold treatment of those non-compliant consignment of oranges,” he said, stressing that there are “no oranges which have been put in free circulation in the EU without this additional treatment.”

While some imports did not follow the new measures and were subsequently carried out at a later stage in the airports prior to shipping, the Commission representative stressed this was a temporary fix and not one that South Africa will be able to rely on going forward.

“[South Africa] is expected to fully comply with the new sanitary measures for all future consignments,” he said.

[Edited by Gerardo Fortuna/Nathalie Weatherald]

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Guava root-knot nematode has been detected in Australia for the first time — so how concerned should farmers be?

ABC Rural

 / By Lucy Cooper and Matt Brann

Posted Mon 31 Oct 2022 at 1:47amMonday 31 Oct 2022 at 1:47am

A women sorts sweet potatoes in a packing room.
The guava root-knot nematode is one of the most damaging root- knot nematodes in the world. (ABC Wide Bay: Brad Marsellos)

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Guava root-knot nematode has been detected for the first time in Australia in the Northern Territory — leaving farmers with questions about what to do next. 

Key points:

  • Guava root-knot nematode has arrived in Australia for the first time in the Northern Territory
  • A expert from the United States is not surprised it has been found here
  • Sweet potato growers have been urged to stay vigilant and report suspected cases

The pest severely impacts sweet potatoes by damaging their roots.

It also stunts the growth of a wide range of other crops, including cotton, cucumbers, capsicums, pumpkins and zucchinis. 

The Northern Territory’s chief plant health officer said the pest had been found in four locations in the territory and the likelihood of eradication was quite low.

So how worried should farmers be and what should they do if they find it on their property?

Fumigation used in the United States

man in black shirt and hands on hips smiles at camera
Dr Johan Desaeger says fumigation is a common control method.(Supplied: University of Florida)

Johan Desaeger, an associate professor from the University of Florida, said he was not surprised to hear the pest had been found in Australia.

“Australia was the last continent, except for Antarctica, where this nematode had not been reported yet,” he said.

“It was first identified in the 1980s in China … but I believe this nematode has been around the tropics and sub-tropics across the world probably for millions of years.”

The nematode was first detected in the United States in 2004.

Mr Desaeger, who co-authored a report on the pest this year, said the nematode liked warm weather and sweet potato farmers in the United States were using fumigation to control it.

“I don’t think it’s had a big impact yet in Florida where I am, although it’s had an impact in North Carolina where it’s been impacting the sweet potato industry — but that’s more of a quarantine issue because the tubers are an ideal (host) to spread this nematode,” he said.

“My advice is to keep monitoring it, keep sampling.

“I wouldn’t go into panic mode, just be cautious and if you see root-knot on any crops, get it properly identified … the more information you have the better.”

He said he doubted it would spread to the temperate climates of Australia.

Keep an eye out for signs

The University of Southern Queensland’s Gavin Ash has been studying sweet potato pests and diseases in Australia and Papua New Guinea for the past decade.

He said root-knot nematodes were like “little tiny eels that live in the soil” and in general were one of the “highest-problem” pests for sweet potatoes.

Sweet potato in a bucket, on the ground in a paddock of rich brown soil.
Guava root-knot nematode has had a severe impact on sweet potato production in the United States. (ABC Wide Bay: Eliza Rogers)

“The problem with nematodes is they’re quite insidious — they’re small, you don’t notice them and then all of the sudden you realise you’re not getting as much yield as you used to get and your yield declines over time,” he said.

“The other really important thing with sweet potato, is that any sort of damage or blemish on the potato makes it unsaleable, because people don’t want to buy a potato with black marks or lumpy bits on them.”

He said there was a risk the guava root-knot nematode was already in Queensland and that it was important for growers to keep and eye out for signs.

“We have other (types of) root-knot nematodes in sweet potato and they’re seen as number one or number two in terms of pests and diseases on the roots, and because they’re in the soil they’re more difficult to manage.”

Queensland farmers concerned

With the threat right on their doorstep, Queensland’s sweet potato growers feel they have been left in the dark.

Wolfies Farms is a major sweet potato producer based in Rossmoya, near Rockhampton in Central Queensland. 

Manager Rodney Wolfenden said he was taken by surprise by the news of the pest.

man stares into camera
Farmer Rodney Wolfenden feels left in the dark about the pest.(Supplied: Rodney Wolfenden)

“I’m not familiar with it at all, it’s not something that we’ve had here previously” he said.

Mr Wolfenden first heard about the pest from a fellow member of the sweet potato industry and said he was yet to receive contact from the Department of Agriculture and Fisheries.

“There has been no contact from the department, the only thing that we’ve seen is a press release, but essentially no information about it — nothing,” he said.

Mr Wolfenden said he was unsure of his next steps.

“I’d like to think that there are attempts made to eradicate it or at least contain it — I’m pretty disappointed that it’s there,” he said.

“The only good thing I can see … is that it has actually been spotted and now we can do something about it.”

Mr Wolfenden said it was the last thing the industry needed.

“We’ve been through a hard time over the last couple of years, we don’t need something like this to turn up,” he said.

“It’s going to affect a wide range of other crops as well — no one needs that sort of thing.”

Farmers urged to report suspected cases

In a statement provided to the ABC, Biosecurity Queensland urged growers in the state to remain vigilant.

“Guava root-knot nematode is a significant threat to horticultural industries as it can be more destructive than other root-knot species on many crops,” it said.

“The risk of spread from the Northern Territory into Queensland and other jurisdictions for plant products and commodities currently traded is considered very low, although the risk for nursery plants is likely to be higher.”

Farmers with suspected guava root-knot nematode on their property were told to report it immediately to Biosecurity Queensland on 13 25 23, online at daf.qld.gov.au or to the Exotic Plant Pest Hotline on 1800 084 881.

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UMaine News

A photo of a leaf damage
Photo by Sarah Fanning, courtesy of Lauren Azevedo-Schmidt.

Insects cause more damage to leaves in recent history than millions of years ago, study finds 

October 12, 2022 

Insect herbivores have caused more damage to plant matter from leaves in recent history than millions of years ago, according to a new study led by a University of Maine postdoctoral researcher. 

Despite global insect decline and biodiversity loss fueled by human activity, the frequency of leaf damage by insects among forest plants in recent history, post-1955, is more than twice that of vegetation from the Pleistocene, 2.06 million years ago, and the Late Cretaceous period, 66.8 million years ago. The unprecedented increase in insect damage on leaf matter could pose negative effects on plant productivity and forest health.

To conduct their study, Lauren Azevedo-Schmidt, a postdoctoral researcher with UMaine’s Climate Change Institute, and her colleagues collected leaf samples deposited within sediment across three modern forest ecosystems — Harvard Forest in Massachusetts, the Smithsonian Environmental Research Center in Maryland, and La Selva in Costa Rica — and compared them to previously published leaf litter and fossil data. 

The research team, which also includes Emily Meineke of University of California, Davis and Ellen Currano of the University of Wyoming, used radiocarbon dates to verify the ages of modern leaves along with quantifying the frequency and diversity of insect damage in each sample.  

The causes of this increase in leaf damage due to insect herbivores and the specific consequences of it remain unknown. However, researchers believe widespread change influenced by human activity, such as the rate of global warming, urbanization and the introduction of invasive plants and insects, could be driving the uptick. Human activity may have drastically changed how insect herbivores are interacting with their food source, the researchers say. 

The research team published their findings in Proceedings of the National Academy of Sciences of the United States of America. 

“Humans understand that climate is always changing and that the Earth has previously been hotter, but we often can’t grasp the ‘oddity’ of modern climate change,” Azevedo-Schmidt says. “The geologic record reported here should have supported comparable levels of insect herbivory, but it didn’t because humans weren’t present in our post-industrial revolution capacity. This shows the heartbreaking reality that humans have a much higher impact on forest ecosystems than increased atmospheric CO2 alone. However, we can work to minimize our impacts on forest ecosystems by considering the intersection of these findings.” 

The researchers also found that the damage caused by insects in leaf samples from recent history is slightly more diverse than that in fossilized leaves. The increase in leaf damage diversity, however, is not as drastic as the spike in damage frequency. 

Researchers examined total damage frequency and diversity along with various types of damage including specialized, piercing and sucking, surface feeding, hole feeding, galling, mining, skeletonization, margin feeding and specialized damage. In addition to discovering an overall uptick in total damage frequency, the team also found an increase across all groupings of damage. 

“Increased insect feeding can’t be explained by one group of insects but rather, all groups of feeding damage analyzed here,” Azevedo-Schmidt says. “This suggests that all insect herbivores within these three modern forests are increasing their feeding damage; complicating the story as we can’t simply blame one species or group.” 

No correlation was identified between damage diversity and frequency, according to researchers. The drivers behind the uptick in damage diversity are also unknown. 

“This is interesting because it suggests that insect diversity isn’t influencing insect feeding frequency and that other drivers are responsible for the drastic increase we are seeing,” Azevedo-Schmidt says. 

According to researchers, insects and plants possess the most diverse lineages on the planet, and how they interact has evolved over millennia in response to natural and unnatural causes. 

How plant-insect relationships change over time, including the extent to which the latter feeds on the former, has implications for biodiversity, plant functionality and mortality, and carbon balance in forests — the loss of plant life can decrease the ability for a forest to absorb atmospheric carbon dioxide through photosynthesis.

“This study is the first to compare similar records of plant-insect interactions across modern and fossil datasets,” Azevedo-Schmidt says. “These findings highlight the importance of humans interacting with landscapes and although climate change influences ecosystem processes, it is not the only factor we need to consider. Humans are agents of disturbance and dispersal, greatly influencing the natural world around us.” 

Contact: Marcus Wolf, 207.581.3721; marcus.wolf@maine.edu

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Predicting potential global and future distributions of the African armyworm (Spodoptera exempta) using species distribution models

Scientific Reports volume 12, Article number: 16234 (2022) Cite this article

Abstract

Invasive species have historically been a problem derived from global trade and transport. To aid in the control and management of these species, species distribution models (SDMs) have been used to help predict possible areas of expansion. Our focal organism, the African Armyworm (AAW), has historically been known as an important pest species in Africa, occurring at high larval densities and causing outbreaks that can cause enormous economic damage to staple crops. The goal of this study is to map the AAW’s present and potential distribution in three future scenarios for the region, and the potential global distribution if the species were to invade other territories, using 40 years of data on more than 700 larval outbreak reports from Kenya and Tanzania. The present distribution in East Africa coincides with its previously known distribution, as well as other areas of grassland and cropland, which are the host plants for this species. The different future climatic scenarios show broadly similar potential distributions in East Africa to the present day. The predicted global distribution shows areas where the AAW has already been reported, but also shows many potential areas in the Americas where, if transported, environmental conditions are suitable for AAW to thrive and where it could become an invasive species.

Introduction

Global trade and transport have historically led to the movement of organisms, mostly for domestication, farming, etc. where they are in a controlled environment1,2. However, some movements of species are unintentional and can result in species becoming invasive in these new areas3,4,5. Invasive species, therefore, can produce massive economic and environmental damage due to their ability to spread without limitations6,7,8; and insects, being the most diverse group of organisms on Earth, are also one of the most invasive9. Some of the major problems caused by invasive insects include human disease vectors and agricultural and forest pests10, often impacting the health and economy of the countries affected11. Some well-known recent examples of invasive agricultural pests are the cotton bollworm, Helicoverpa armigera (Hübner), the diamondback moth, Plutella xylostella (Linnaeus), and the fall armyworm, Spodoptera frugiperda (J. E. Smith)12,13,14.

The African Armyworm (AAW) is the larval stage of the noctuid moth Spodoptera exempta (Walker, 1856). Like other armyworms15, AAW is considered a major pest species, historically the most important after locusts in parts of Africa16,17. AAW often occurs at high larval densities, causing outbreaks and, therefore, significant economic damage to crops and pasturelands16,18. The species is widely distributed across sub-Saharan Africa, where it especially affects Central, Eastern and Southern Africa, but the presence of the species has also been reported in Arabia, Southeast Asia, and Australia19,20,21. AAW caterpillars are a major pest of cereals and grasses, including some of the most economically important crops such as maize, rice or wheat22. Generally, low-density populations of the larvae persist throughout the continent, usually going unnoticed as they are in small numbers and have a cryptic coloration23. Many studies (e.g.24,25,26) have pointed out that it is after the first (short) rainy season in East Africa (around November or December) that the ‘primary’ (first) outbreaks occur. These outbreaks are caused by the mating and oviposition of the adult moths emerging from the low-density (dry season) populations, which are dispersed and scattered by the rainy season winds and end up concentrating in patchy areas where rainfall occurs27,28, that is thought to be due to convergent wind flows23. After these primary outbreaks, the long rainy season initiates a series of ‘secondary’ outbreaks, throughout eastern and central Africa, which may cause massive damage to crops, and can be monitored and predicted thanks to meteorological observation and monitoring27,29,30. In some countries, like Zambia, its maize production in 2012–2013 was reduced by 11% due to AAW attack31 and in 2017 it was estimated that 30–40% of the crop production could have been lost due to this pest32.

Since at least 1930, AAW outbreaks and moth trap data, as well as some meteorological data, have been collected in the most affected countries, including Kenya and Tanzania16,21. Subsequently, these data have been digitised and incorporated into data management and information systems, such as WormBase33, which was developed in the 1990s to aid in the prediction of AAW outbreaks. In the present study, we use forty years of AAW outbreak data to model the environmental suitability of the pest.

Species distribution models (SDMs) are modern tools that are used to characterize and predict the present and future distribution of a species, using species distribution data and environmental variables that affect, directly or indirectly, the species’ ecological niche or environmental suitability34,35,36. This provides a very useful tool for pest management activities, as it can help identify areas where the species might be present or vulnerable areas for the pest37,38,39. SDMs have been used to model the environmental suitability of other similar pest species, such as the fall armyworm, S. frugiperda, FAW, which is native to the Americas, but has recently invaded and spread throughout sub-Saharan Africa, into areas where the African armyworm is endemic14. This work was used to predict new areas in the world that could be suitable for FAW expansion, including parts of Asia and Oceania; predictions that have subsequently been realised (https://www.fao.org/fall-armyworm/monitoring-tools/faw-map/en/). Although the distribution of S. exempta in Africa and Arabia has been well established for at least 40 years21, and much is known about its feeding and migratory behaviour16, there is little information about its broader environmental requirements.

In this study, we generate the first predictive environmental suitability models for the African armyworm, using species distribution modelling techniques. We use occurrence data from reported larval outbreaks in Kenya and Tanzania, and variable selection methods to define the principal environmental variables that affect the geographical distribution of S. exempta. The generated models, which are local to Kenya and Tanzania, predict the present and future environmental suitability of the species under three different future-climate scenarios. For predicting the present suitability, we used the outbreak data from 1969 to 1990 and contrasted the generated model with the rest of the data, from 1991 to 2008. This meant we validated our model against data that are more independent than used in the majority of SDM studies, a highly recommended approach40. For the three future climate scenario models, we used all the outbreak data from Kenya and Tanzania, from 1969 to 2008 to forecast the 2061–2080 time period. We also model the global environmental suitability for the species by extrapolating these local data to the rest of the world to assess its invasion potential. Finally, we determine if models suggest that the African armyworm’s future distribution will likely intersect areas of cropland, which could demonstrate a need for preventive and control measures to target the vulnerable areas before they are attacked.

Results

Variable selection

The variable selection through PCA narrowed the environmental suitability components to five (Table 1). The variables are related to temperature and precipitation, and the AAW response to them can be seen in Fig. 1. Bioclim 07 (temperature range throughout the year) suggests that AAW do best in locations where the temperature variation is greater than around 12 °C annually. Variable Bioclim 08 is related to temperature during the wettest quarter and seems to suggest that AAW prefer temperatures between 15 and 25 °C during the rainy season, and anything greater than 25 °C is much less suitable. Variable Bioclim 15 is related to the seasonality of precipitation and suggests that AAW do best when rainfall varies by around 80–100 mm annually. Finally, Bioclim 13 and 17 are related to the amount of precipitation during the wet and dry season, respectively. During the wettest month, it seems to require a minimum of around 100 mm rain, but also seems to have a maximum of around 300 mm rain, above which it is less suitable, perhaps indicating its susceptibility to floods. During the driest quarter, it seems to be more versatile and can tolerate a wide range of precipitation, but there appears to be a minimum rainfall of around 10 mm, indicating that is also susceptible to drought.Table 1 Variables selected by the PCA for the S. exempta environmental suitability models.

Full size table

figure 1
Figure 1

Model performance

The receiver operation characteristic (ROC) curve is a graphical way of illustrating the model’s ability to distinguish between binary classes at various threshold settings, and area under the curve (AUC) of the ROC is a value that measures the degree to which these classes can be distinguished between. This means that the closer to 1 the AUC value is, the better the model will be at separating classes, which in this case would be the environmental suitability of the species. AUC values of our models are considered to be ‘excellent’41, and TSS, values are considered ‘moderate’ and ‘substantial’42, therefore showing a good performance of the models, and that they are robust and accurate (Table 2). This indicates that the ecological suitability suggested by the generated models resemble the real probability of occurrence of the species, and therefore, its possible distribution.Table 2 Internal evaluation statistics for the generated species distribution models (SDMs) generated.

Full size table

Environmental suitability of S. exempta

Present-time environmental suitability models for the AAW in Kenya and Tanzania (Fig. 2A) show high suitability in the south and west of Kenya and the north and centre of Tanzania. These areas coincide with the occurrence points from the outbreak data used (blue dots in Fig. 2A); outbreaks are usually reported on crops such as maize, so it is likely that environmental suitability overlaps with agricultural land use. These suitable areas also coincide with sub-humid and tropical highlands; the paler or non-suitable areas coincide with more arid conditions, such as north-eastern Kenya43. Figure 2B shows a land use map extracted from Ref.44, indicating that the vegetation in the suitable areas of our model (Fig. 2A) are mainly grasslands, savannas and croplands. Regarding the prediction of the 1991–2008 outbreaks, all the points (yellow dots in Fig. 2A) seem to fall in areas with medium to high suitability, with AUC = 0.90, considered as ‘excellent’41, which indicates the model can accurately predict the areas that are suitable for outbreaks in the near future.

figure 2
Figure 2

Future and worldwide environmental suitability scenarios

Figure 3 presents three maps that show the difference in environmental suitability between present-time and three different CO2 emission scenarios between 2061 and 2080 in Kenya and Tanzania. The outputs of the three scenarios are very similar to each other. Scenario SSP1-2.6 (a gradual decline in CO2 emissions) show fewer gained areas (74,075 km2) than lost (109,500 km2), and the same happens with the extreme CO2 emission increase scenario—SSP5-8.5 (70,425 km2 of gained areas; 161,425 km2 of lost areas). Gained areas (109,625 km2) for scenario SSP3-7.0 (gradual increase in CO2 emissions), are however similar to the lost areas (106,350 km2). These results depict a future where the species seems to have a limited spread. Gained areas coincide mainly with cropland and grassland45,46. This all suggests that climate change might help the AAW distribution to expand and take over areas of grassland and cropland; but also limit its expansion in other areas where too many emissions might destroy these grasses and crops.

figure 3
Figure 3

The world environmental suitability model shows a marked high suitability in tropical areas, especially related to high, but not extreme, temperatures and precipitation (Fig. 4). It appears that the suitability overlaps the distribution of grasses, which is historically the main food source of the AAW, as it is noticeable in the Savannas, Pampas and Veldts, and seems to be delimited by arid areas and tropical deserts (e.g. Sahara, Kalahari, Atacama, etc.) as well as areas of extreme rainfall like rainforests (e.g. Amazon, Congo River Basin, South East Asia and Australian). However, as the models have only been constructed with climatic variables and not land use rasters, we cannot be completely certain that these forested areas could be suitable if converted to agriculture.

figure 4
Figure 4

When looking at the recorded distribution of AAW globally21 (Fig. 5), it very much resembles the world environmental suitability model (Fig. 4). Grey areas show where the projections are extrapolated outside of the climate conditions used to build the SDM, according to the results of the MESS approach47. Projections in these areas should be treated with extreme caution, as there is no way of knowing how accurate they are. In Africa, there is high suitability in the eastern, western, and central areas, where larval infestations have been recorded, even on the west of southern Africa. Madagascar is also predicted to be suitable for AAW outbreaks, although no larval infestations have been recorded there to our knowledge, but moth specimens have been found, indicating the possibility of being there. In Arabia, which has extensive larval infestations, only a limited area is predicted to be suitable, and with only medium suitability, probably due to it not being a very suitable climate, but in practice, irrigation could have permitted its viability and expansion. There is very high suitability in the west and south of India, and Sri Lanka (Figs. 45), which coincides with the ghats where grasses are present, but the species has not yet been recorded there. Many AAW larval infestations and outbreaks have been reported in southern (but not northern) parts of Southeast Asia and the western Australian coast, coinciding with areas of medium to high suitability. With the exception of Hawaii48—where the model shows high suitability—the species has never been reported in the Americas. Nonetheless, the model does predict very high environmental suitability in some countries like Brazil, Colombia and Mexico (Fig. 4), which sets an alarm for its potential distribution and settlement if the species was to reach those areas. All this indicates that the model has been able to predict most of the actual worldwide distribution, using a database limited to a relatively small area in East Africa, and therefore, that it is a robust model.

figure 5
Figure 5

Discussion

In a world in which crop production often revolves around extensive monocultures, and global changes in climate and trade facilitate the spread of insect crop pests, there is increased potential for the introduction and spread of invasive species49,50,51. Understanding the environmental requirements of potentially invasive crop pests can identify areas at threat and facilitate targeted monitoring. Some authors have previously tried to do this by generating current or potential Species Distribution Models. Examples include important invasive pest species, such as the cotton bollworm, H. armigera, the diamondback moth, P. xylostella, the gypsy moth, Lymantria dispar (L.), the spotted wing drosophila, Drosophila suzukii (Matsamura), the European paper wasp, Polistes dominula (Christ), and the fall armyworm, S. frugiperda12,13,14,52,53. In this study we have constructed SDMs for the African armyworm, S. exempta, a pest endemic to sub-Saharan Africa. Our results identify those climatic variables that seem most important in determining the geographical distribution of AAW and provide a robust SDM for Kenya and Tanzania in the present time, as well as three different future climate change scenarios. We expand this to a predictive worldwide model that identifies areas, especially in the Americas and South Asia, where AAW has the potential to become invasive if it were introduced.

Selected variables for the environmental suitability of African armyworm outbreaks are mainly related to annual temperature variation and precipitation, especially during the wettest quarter, which is the rainy season. The rainy season plays an important role in the movement of AAW adults in Africa, as the winds that occur during it are key for the dispersal of the adult moths. Existing literature23,26,29,54 indicates that adult moths migrate along the dominant winds to grassland areas or crops, where they feed, causing subsequent larval outbreaks in nearby areas where they can disperse or migrate to. Precipitation outside the rainfall season is important for the low density populations of AAW that persist in these areas where outbreaks have occurred, during the dry season, as it stimulates the growth of grasses, providing the AAW with suitable habitats for feeding and breeding55, which could explain why variables like ‘precipitation seasonality’ or ‘precipitation of the driest quarter’ have been identified as important explanatory variables. Nonetheless, the areas where outbreaks occur (which we modelled) are not always the same as the ones where low-density populations settle (which we did not explicitly model). Temperature changes affect the species distribution too because, being ectotherms, their development and survival are temperature-dependent56.

The local present-time model depicts a robust environmental suitability for S. exempta in Kenya and Tanzania (Fig. 2A). Low environmental suitability coincides with arid or semi-arid areas, which may seem evident as extreme temperatures and dry conditions are not ideal for the development of its eggs and pupae56,57. Indeed, water and ambient humidity scarcity can affect the water balance of insects, impacting their survival, development and even their population dynamics, as seen in similar species, the FAW58. Climatic conditions in these areas can also affect its suitability indirectly. For example, changes in the water content and concentration of nitrogen and other minerals of the host plants, can negatively impact AAW adults’ fitness59. Additionally, plants that grow in arid or semi-arid areas are not suitable host plants of the AAW16, which mainly feeds on Graminae, and these require a certain level of humidity for their development. According to the generated model, sub-humid and tropical highlands are the most suitable areas for the AAW and, the known distribution of the AAW, besides the biology of the species, coincide with these areas. During the dry season, low-density armyworm populations are usually found in the highlands as the low temperatures extend their development16, which may explain why these tropical highlands are highly suitable. Looking at land cover and vegetation maps (e.g.44,45), the vegetation present in the suitable areas are mainly grasslands, savannas and croplands, which are the main host plants for the AAW.

The predictions of the environmental suitability for the 1991–2008 outbreaks (not included in the training dataset), appear to be accurate and robust, indicating that modelling present environmental suitability can be useful to predict outbreaks in the near future. These predictions can also be combined with population dynamic studies to predict outbreaks of the next few years, like other authors have previously done30,60,61.

Local future-scenario models (Fig. 3) are useful to predict where the species might be present in some years’ time. It is evident that climate change is altering the environmental conditions, therefore redesigning where species can live. It has been thoroughly documented that the distribution of many species is shifting to new areas, as well as disappearing from others62,63,64. This is especially important in pest management as predicting new areas could help set control measures for those areas and prevent outbreaks39,65,66. Although we produced models for three different CO2 emission scenarios, they all portray similar results, where there are suitable areas being both gained and lost. A positive side to this similarity in suitability is that management and control plans will probably be effective in all scenarios. On the other hand, it is interesting that such an aggressive pest like the AAW is predicted to show a slow expansion of their distribution, if compared to other similar pest species like processionary moths (Thaumetopoea spp.) or the box tree moth (Cydalima perspectalis)67,68. Climate change will likely alter the environmental suitability of all living organisms as it challenges their physiological limits69, and there is evidence that the geographical distribution of crop pests is moving increasingly polewards in response to climate change70,71. Due to this, it would be assumed that the expansion of the suitable areas would be much quicker or extensive, but these results might indicate the contrary, that climate change could reduce the suitable areas for its expansion. Factors affected by climate change, such as temperature, rainfall and relative humidity, seem to have mostly positive effects on fecundity and development of migratory pests like locusts72,73. However, for other lepidopteran pest species, like H. armigera, climate change has negatively affected its survival and reproduction74,75. Climate change is also reducing the amount of rainfall, which has had an impact on the ecosystem dynamics and vegetation structure of grasses in South Africa reducing grassland areas76, but also grass productivity, shifting these grasslands to shrubland and other tree-dominated biomes77,78. As grasses are the main food source for the AAW, it is coherent that all these lost suitable areas in our future scenario models might correspond to grass areas shifting to other vegetation patterns.

Global environmental suitability in the African continent resembles very much the previously reported distribution of African armyworm21 and appears in nearly all the same areas, that is, sub-humid areas, grasslands and croplands. Haggis’ study indicated that AAW has been recorded in India, South-East Asia, and Australia, where the models do predict a high environmental suitability, even though their presence there had not been used to generate it. This shows that the models are competent and can predict real areas where the species might expand into. There are areas, nevertheless, where the model does not predict high suitability, but the species has been recorded, like some parts of Indonesia, Arabia, and southern Africa. This could be due to the sample size and its limited geographic extent. Many authors (e.g.79,80) have reviewed this issue and it does seem to affect the accuracy and performance of SDMs. As our database is limited to Kenya and Tanzania, the selected variables will extrapolate to areas where the conditions are similar, that is why the prediction of suitability outside the tropics is not as accurate, as shown by the results of the MESS approach. Projections into colder regions seem likely to be inaccurate due to the variable response (Fig. 1), which have a clear upper limit. However, projections into areas with higher or lower precipitation rate might be more trustworthy due to a wider tolerance to change in precipitation26. Nonetheless, the worldwide model seems to predict an accurate environmental suitability in general.

In the global environmental suitability model, areas where the AAW has not been recorded but have a high suitability are intriguing. These are mostly in the Americas, especially between the tropics, where the climatic variables define the AAW’s niche. They also include coastal regions where there are grasses, like Pampas; or open woodlands, but also avoid tropical rainforests or arid areas due to their extreme conditions. The global environmental suitability of the AAW mirrors the environmental suitability and distribution of the FAW14 which has very similar environmental requirements, making them potentially competing species. The FAW, which is native to the American continent, was introduced into Africa, probably due to transportation of plants and crops, and rapidly spread to become one of the most important crop pests on the continent. Another example of this is H. armigera, which made a jump from Africa and Europe to the American continent13. The global model suggests that a similar thing could happen with the AAW on the American continent if it were introduced. Countries like Brazil, which is one of the world’s biggest maize producing countries could, in time, become hotspots for the AAW and enhance this global problem. Our models, and the variables used however, do not consider anthropogenic factors that could increase the migration and dispersal of S. exempta, such as global connectivity and human-mediated transport81, as it has been done for the fall armyworm14. If considered in future studies, this could confirm our findings about S. exempta ability to disperse throughout the American continents, which has already been considered as a potential risk82. This manifests the importance of revisiting and tightening international agricultural biosecurity, as invasive species are transported to new territories in a daily basis, aggravating the problem83,84.

Characterizing the climatic variables that explain or delineate the AAWs niche will help with a better understanding of the species’ biology and its possible management85. Future and global scenario models based on climatic variables, like the ones used in this study, are important to understand how invasive pest species might react to climate change or new areas if they are transported there. In fact, IPM studies often use these SDMs and niche characterization86 of important pest species such as the fall armyworm, S. frugiperda15, underlying its importance. However, to understand how the species will disperse in space and time, models should be used as part of a bigger research effort, including natural competence, or anthropogenic factors, such as bias in outbreak reporting, land use and management, transport, etc.

Finally, it is worth noting that SDMs are generally only used to predict suitable abiotic environments and seldom include detailed information regarding the presence of potential competitor species or natural enemies. Invasive fall armyworms have rapidly expanded throughout the African continent and globally88. It is considered a very aggressive and cannibalistic alien pest89,90 and feeds on a range of plant species, including the cereals and grasses that AAW specialises in, meaning there is a possibility of displacement, as it appears to be doing with other sympatric species, such as the Asiatic pink stem borer, Sesamia inferens (Walker) or the maize stalk borer, Busseola fusca (Füller)91,92. Given this, it is possible that although our SDM suggests that parts of the Americas are environmentally suitable for AAW to invade, in this environment it would be potentially competing with the native FAW, which is much more aggressive than AAW and is likely to be the stronger intra-guild competitor. It is therefore possible that AAW has previously reached the Americas but has failed to establish there due to competitive interactions with FAW or other natural enemies.

Materials and methods

Distribution data compilation

The presence records for Kenya and Tanzania were obtained from an updated version of WormBase33, which is a data management and information system that includes AAW outbreak and trap data for both countries since 1969. Outbreak data were used for the present study, where only presence records with defined geographic coordinates, following the WGS84 geographic coordinate system were used. Presence points that were inaccurate and duplicates were filtered using ArcGIS Pro. In total, 721 occurrence points, from 1984 to 2008, were obtained. 568 occurrence points were recorded from the years 1969–1990, and were used to make the first model, which predicted the current distribution.

Environmental data

Species Distribution Models (SDMs) require selecting biotic and/or abiotic environmental variables that relate to the distribution of the modelled species40, and to minimize uncertainties in modelling predictions it is important to understand which variables are more significant to the species by performing a good variable selection93.

Variables used in this study were the WorldClim Version 294 bundle of 19 global climatic layers from 1970 to 2000 in a 5 × 5 km resolution; and WorldClim CMIP Phase 6 (CIMP6)95 global climatic layers for future suitability models. We selected the 2061–2080 period for the BCC-CSM2-MR General Circulation Model (GCM)96 and three Shared Socio-economic Pathway (SSP): SSP1-2.6, which shows a gradual decline in emissions; SSP3-7.0, which would be an intermediate scenario where the CO2 emissions continue to rise in a similar fashion to now; and SSP5-8.5, which shows a dramatic rise in CO2 emissions97.

Variable selection

In previous modelling studies for the fall armyworm14, the variable selection was based on the life-history and environmental requirements for the species. Nonetheless, other studies98,99,100 suggest other analyses, such as Ecological Niche Factor Analysis (ENFA) or Principal Component Analysis (PCA), may be more robust, as they result in uncorrelated variables. This both eliminates information that might be redundant and means that the forecasts are not affected by changes in the correlation between environmental variables between time periods or regions. We followed the methodology described by Gómez-Undiano, 2018100, a method derived from Petipierre et al.98, which showed that a PCA resulted in a more accurate variable selection for better models. Therefore, we did a PCA with all the previously chosen variables and reduced the number to some main ones, based on the variance explained in the presences of S. exempta; this being the variables that had the greatest loadings on some of the PCA axes. The variables used for the future predicted suitability were the same as the ones resulting in the PCA, but from the 2021–2040 bundle. The variable selection was carried out in R v.4.0.2101 using RStudio v.1.3.1093.

Modelling environmental suitability

SDMs can be generated only with presence points but this can result in inaccurate and biased models102, so often, absence points are used too. However, absences are difficult to obtain, especially for mobile species like insects. However, studies suggest that selecting pseudo-absences, which could be generated randomly, helps to improve the quality of the models and their accuracy102,103,104. We followed the BIOMOD modelling algorithm105, using the ‘biomod2’ package106 in R for pseudo-absence generation, and selected 700 pseudo-absence points for the local distribution models in Kenya and Tanzania, to match the number of occurrences104. When extrapolating pseudo-absence data to the rest of the World, some authors107,108 suggest delimiting a geographical background to which the species could reasonably disperse, can improve SDM. We generated a background area (for the Worldwide ensemble model) of the limited area of Kenya and Tanzania to reduce extrapolation of the variables to non-analogue areas.

Predicting global suitability from a limited area, such as Kenya and Tanzania, means that predictions could be extrapolated to areas with very different climate to Kenya and Tanzania, which could be highly erroneous. To ensure the predictions are only made in areas with conditions similar to those in the data used to construct SDMs, the Multivariate Environmental Similarity Surface (MESS)47 was calculated using the R package ‘dismo’109.

Choosing one modelling statistic method can be challenging because different methods have advantages and disadvantages and tend to produce variable predictions. However, ensemble modelling results in producing more robust and reliable models110,111. We created an ensemble that includes five algorithms based on logistic regression and machine learning: artificial neural networks (ANN), classification tree analysis (CTA), flexible discriminant analysis (FDA), generalised additive models (GAM), generalised linear models (GLM), MaxEnt, random forest (RF) and Surface Range Model (or BIOCLIM). This process was undertaken using default parameters from the ‘biomod2’ package in R.

To evaluate the accuracy and robustness of the ensembled models, internal validation, which is included by default in the ‘biomod2’ setting, was used. We split the distribution data randomly into two, with 70% being used for the SDM calibration and 30% the validation set, using the area under the curve (AUC) of the receiver operation characteristic (ROC), and true skill statistic (TSS). 100 replicas were generated for each algorithm used, and models for which validation with AUC > 0.7 or TSS > 0.6 were selected to generate the final ensembles. Although studies generally use a 70–30% data split for the training and testing data e.g.14,112, we also generated additional models with different data-splits (10, 20, 30, 40, 50, 60, 80 and 90%) to ensure the model validation was robust (Supplementary Materials). External validation of the predictive model was constructed using outbreak data from 1969 to 1990 was also performed, by calculating the AUC of the model against the outbreak points from 1991 to 2008 as the validation set.

In total, three ensemble models showing environmental suitability for S. exempta were generated: (1) a predictive local model using recent (1970–2000) environmental conditions for Kenya and Tanzania and outbreak data sub-sample from years 1969 to 1990, which was validated against more recent data (1991–2008); (2) a present-time local model for Kenya and Tanzania using all outbreak data (1969 to 2008) with three projections for three CO2 emission scenarios (A. SSP1-2.6; B. SSP3-7.0; and C. SSP5-8.5) between 2061 and 2080; and, (3) a Worldwide present-time model using all outbreak data (1969 to 2008).

When looking at the future-scenario models, it is sometimes difficult to determine which are new areas that are more or less suitable for S. exempta. To make it easier to visualise, we converted the future scenario model projections and the present time model (using all the outbreak data) into binary maps using the cut-off values, based on TSS, of each projection. Then we combined each future scenario model projection with the present time one to get a categorical map showing new suitable and non-suitable areas.

Data availability

The datasets generated during and/or analysed during the current study will be available in the DRYAD repository, after the manuscript is accepted [https://datadryad.org/stash/share/t-EgQOweHgcOHQ_paK1ao6PQuRsnjkGCSh63_HD4n00] with DOI number [https://doi.org/10.5061/dryad.sbcc2fr9b].

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Acknowledgements

The authors thank Ian Stevenson for assistance with the database and analysis and the many farmers, extension workers and government officials who contributed to data collection over the 40 years of this study.

Funding

The funding was provided by Biotechnology and Biological Sciences Research Council (BB/P023444/1).

Author information

Authors and Affiliations

  1. Lancaster Environment Centre, Lancaster University, Lancaster, UKIrene Gómez-Undiano & Kenneth Wilson
  2. State Department for Crop Development & Agricultural Research, NARL Kabete, Waiyaki Way, Nairobi, KenyaFrancis Musavi
  3. Crop Bioscience Solutions Ltd., Arusha, TanzaniaWilfred L. Mushobozi
  4. Pest Control Services, Ministry of Agriculture and Food Security, Arusha, TanzaniaWilfred L. Mushobozi & Grace M. David
  5. CABI, Nairobi, KenyaRoger Day
  6. Centre for Ecology and Conservation, University of Exeter, Penryn, Cornwall, UKRegan Early

Contributions

I.G.U. and K.W. conceived the ideas of the project; I.G.U. designed the model and the computational framework, analysed the data, and took the lead in writing the manuscript, with the help of K.W.; R.E. aided in interpreting the results and worked on the manuscript. F.M., W.L.M., G.M.D. and R.D. contributed to the interpretation of the results and to the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

Corresponding author

Correspondence to Irene Gómez-Undiano.

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Wednesday, 28 September 2022 08:23:46

Grahame Jackson posted a new submission ‘Sugary poo could be used to lure destructive plant pests to their doom’

Submission

Sugary poo could be used to lure destructive plant pests to their doom

Newswise

Male spotted lanternflies are strongly attracted to smell of honeybee produced by male conspecifics
by Frontiers

Spotted lanternflies communicate through their smelly excretions  ̶  called honeydew, reports a new study in Frontiers in Insect Science. This invasive species has been impacting crops in the northeastern US, but little is known about how these insects locate each other for reproduction or feeding. According to this latest research, the insects’ honeydew emits several airborne chemicals that attract other lanternflies. Surprisingly, these effects are sex-specific, which may be the first known case of such signals in insects known as planthoppers.

“This research is important because the first step to managing any pest is to understand their biology and behavior,” said Dr Miriam Cooperband of the United States Department of Agriculture Animal and Plant Health Inspection Service, Plant Protection and Quarantine Division (USDA APHIS PPQ) in the US. “As we learn more about the behavior of the spotted lanternfly, we hope to find a vulnerability that we can use to develop pest management tools to reduce its population and spread.”

Attractive scents

Although these insects are known to leave their excretions throughout the understory, they have the peculiar habit of coming together in huge numbers on only select tree trunks. Other tree trunks are mysteriously left untouched. These multitudes of lanternflies can secrete so much honeydew that the surface of the tree becomes white and frothy, as well as emitting a smell of fermentation.

To study the signals sent by these excretions, Cooperband and her collaborators collected honeydew samples separately from male and female lanternflies in the field, to test in the lab. The researchers then gave lanternflies a choice between areas with or without the different types of honeydew to see what attracted them. 

Surprisingly, males were strongly attracted to male honeydew, while both males and females were only slightly attracted to female honeydew. Although it’s still unclear what would cause this behavior, this is consistent with observations of how these insects behave in the field.

The team went on to analyze the different components of the honeydew to determine which produced the strongest signals. Five molecules were tested for attraction and found to have specific sex-attractant profiles. Two molecules called benzyl acetate and 2-octanone attracted both sexes, one molecule called 2-heptanone attracted only males, one molecule 2-nonanone attracted only females and one molecule, 1-nonanol, repelled females, but not males.

Pest control

These findings are just the beginning for better understanding how to potentially control this invasive pest. There are many more questions, such as whether there are seasonal variations in this behavior, and whether there are interactions with microbes in the honeydew that produce the necessary chemicals.

“Spotted lanternfly behavior and communication is quite complex, and this is only the tip of the iceberg. In addition to our work studying chemical signals, such as those in honeydew, we are also interested in the role of substrate vibrations in their communication system,” said Cooperband. “Future research might focus on understanding how they locate each other when they gather and find mates using multiple types of signals.”

Original paper: https://www.frontiersin.org/articles/10.3389/finsc.2022.982965/full


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Contribute to CABI’s new Plant Health Cases

Real-life examples of plant health in practice. 

About Plant Health Cases

Fresh green soy plants on the field in spring. Rows of young soybean plants . High quality photo

CABI, together with Editors in Chief Lone Buchwaldt, David B. Collinge, and Boyd A. Mori is embarking on a new type of online publication called Plant Health Cases.

Plant Health Cases will be a curated, peer-reviewed collection of real-life examples of plant health in practice. This will be an invaluable resource for students, lecturers, researchers, and research-led practitioners. We will be developing cases in all areas relevant to plant health, including:

  • plant diseases
  • plants pests
  • weeds
  • environmental factors
  • agronomic practices
  • diagnosis, prevention, monitoring and control
  • international trade and travel

What is a Case Study?

A Plant Health Case is a relatively short publication with a well-defined example of research in plant health, e.g. a study which results in reduced impact from a disease or pest problem. Cases should be between 3000 and 5000 words long, and can include photos, figures and tables. They should be written in an engaging style that is both science-based and accessible using a limited number of references. Importantly, each case should suggest points for discussion to broaden the reader’s horizon, inspire critical thinking and lead to interactions in the classroom or field.

Interested in Contributing to Plant Health Cases?

We are currently looking for contributions of case studies, and we welcome your ideas! You may have existing case study material ready prepared for use in teaching, or a good example of research in plant health which could be easily adapted to our template. For further information and guidance on how to submit your idea for a case study please see here: https://www.cabi.org/products-and-services/plant-health-cases/

Your submission will be peer-reviewed, and a DOI assigned at the time of publication similar to your other scientific publications. The corresponding author will receive £100 upon acceptance of the final case study. 

Publication Plan

We’re aiming to launch Plant Health Cases in mid-2023. Our case studies will offer practical, real-life examples in one easily searchable platform. All users will be able to search, browse and read summaries of case studies. Full text access will be available via individual or institutional subscription, or by purchasing a single case study.

Further Information

Please get in touch with Rebecca Stubbs, Commissioning Editor, CABI

r.stubbs@cabi.org

About CABI

CABI is a not-for-profit, scientific research, international development and publishing organisation. Unlike other publishers, we use our surpluses to support scientific and rural development projects that help improve the lives of the world’s poorest people, which means that by publishing with us, you are helping to improve the lives of some of the world’s poorest people. Please visit our website at www.cabi.org

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Global Agriculture 

New research maps potential global spread of devastating papaya mealybug pest

   Delhi Bureau  1 Comment Biopesticides & BiocontrolsCABI  4 min read

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10 November 2020, UK: CABI scientists have mapped the potential global spread of the devastating papaya mealybug (Paracoccus marginatus), highlighting new areas in Africa, Asia and the Americas into which this pest could potentially invade.

Also Read: BASF commits to targets for boosting sustainable agriculture

The papaya mealybug, which is native to Mexico and Central America, can have severe impacts upon livelihoods and food security. In Ghana, for example, infestations led to a 65% yield loss which reduced export earnings and resulted in the loss of 1,700 jobs.

Using location data received through collaborations with Kerala Agricultural University, India; the National Rice Research Institute, India; the Bangladesh Agricultural UniversityUniversity of Queensland, Australia; the International Institute of Tropical Agriculture (IITA); Fujan Agriculture and Forestry University in China and CSIRO, researchers were able to model the potential distribution of this pest, taking into account environmental conditions, and the distribution of suitable host crops and irrigation patterns.

The researchers, led by CABI’s Dr Elizabeth Finch, believe the polyphagous insect pest, which affects over 200 plants including economically important crops such as papaya, cassava and avocado, could spread to areas such as the south of the Democratic Republic of Congo, northern Cameroon, Zambia, Madagascar and western Ethiopia which are environmentally suitable and have suitable crop hosts.

In the Americas, the research, published in the journal Pest Management Science, suggests papaya mealybug could extend into El Salvador, Honduras, Nicaragua, and Panama – although the scientists believe it could already be in these locations but its presence is yet to be confirmed.

Whilst papaya mealybug is already present in Florida, where it is under successful control as a result of the release of endoparasitoid wasp species – Acerophagus papayaeAnagyrus loeckiAnagyrus californicus – suitable conditions for this pest are also present in the southern tip of Texas.

Conditions are likely to be too cold in the rest of the USA for permanent papaya mealybug populations, however the research showed that seasonal populations could survive in California, along the Pacific coastline and in the central and eastern states of the USA during the warmer summer months.

Also Read: FMC Corporation Recognized at 2020 Crop Science Awards

In Asia, the areas with suitable conditions were more expansive than the areas with known populations of papaya mealybug, suggesting the potential for further expansion of papaya mealybug specifically in India, Southeast Asia and the southern regions of the Guangxi and Guangdong provinces of southern China.

However, in Australasia the risk is low as only a small amount of fragmented land along the north-eastern side of Queensland, from the very northern tip of Queensland to Bundaberg, is climatically suitable. This is due to heat stress from the high temperatures on the continent.

Similarly, in Europe – though due to cold rather than heat stress – widespread distribution of papaya mealybug is not expected, with only a very small area of land surrounding Seville in Spain and around Sicily in Italy having suitable conditions for resident populations.

Dr Finch said, “This pest has been so successful due to its quick development and prolific reproductive capacity. It has the potential to spread to new areas and rapidly reach high numbers unless suitable phytosanitary or control methods are implemented.

“Information about the papaya mealybug’s potential distribution is important as it can highlight key areas susceptible to invasion, giving an early warning to decision makers, allowing them to put into place phytosanitary measures to prevent or slow the invasion of the pest into their jurisdiction.”

Dr Finch added, “In areas where the papaya mealybug has become established and reached a high enough population density, the use of parasitoids – such as Acerophagus papayae and Anagyrus loecki – remains an effective potential control method.

“Further ecological niche modelling of these parasitoid species is recommended to anticipate their survival, fitness and ultimate biological control impact in areas into which papaya mealybug could potentially expand and become established.”

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