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Zoologger 18 September 2017
Sacrificial virgin spiders let their nieces eat them alive

spider virgin

Anja Junghanns
By Sandhya Sekar

Species: Stegodyphus dumicola
Habitat: Massive spider webs in southern Africa

It takes a lot to be a good aunt if you’re a velvet spider. In fact, it takes your internal organs. After tending lovingly to your sisters’ eggs and regurgitating food for newborns, it’s time to offer yourself as the main course for the spiderlings to suck you dry.
“[The] spiders literally start feeding on the female while she is alive,” says Trine Bilde at Aarhus University in Denmark. The spiderlings inject enzymes to dissolve her innards and suck out the semi-digested fluids, leaving only the outer shell. “But there is no apparent aggression. It looks as if females are almost inviting spiderlings to feed on them.”
More deadly spider strategies: Watch how spiders use sticky silk to win wrestling match
S. dumicola are social spiders that live in large communal nests. Hundreds cooperate to capture prey, defend the nest and take care of the young. The nest is a dense retreat of silk and plant material, with two-dimensional webs to catch prey. Each spider only lives for a year, so can only reproduce once.
In the closely related species S. lineatus, only mated females care for spiderlings. In these spiders, the act of mating seems to cause females to care for other offspring as well as their own – an act called “alloparenting”. However, there are limits: they only let their own spiderlings eat them. Letting your kids eat you is a surprisingly common behaviour known as “matriphagy”.

Eat me!
Bilde and her colleagues wanted to find out whether unmated S. dumicola females also perform alloparenting duties. They bred spiders in the lab and placed them in groups, each with two mated and three virgin females, along with some spiderlings, to observe their behaviour.
Both virgin and mated females performed all forms of alloparenting. They tended to egg sacs, regurgitated food for spiderlings and finally offered themselves up as a meal.
This extreme behaviour makes sense because the spiders in a nest are all closely related and share genes. There are many more females than males, and only certain females reproduce, so the spiders in a colony are genetically similar.
“The investment in these offspring is an investment in her lifetime reproductive success,” says Bilde. “The more gene copies she propagates to the next generation, the better, so providing your body as food is a sensible evolutionary solution.”
“I suspect that females merely aren’t capable of discriminating between their egg cases and someone else’s,” says Jonathan Pruitt at the University of California, Santa Barbara. “The colony is composed of close kin, so even if females produced their own egg cases, there would still be a benefit of assisting a closely related relative.”
The spiders’ environment may also be a factor. “Spiders in the genus Stegodyphus occupy arid landscapes, deserts, where prey is mostly scarce,” says Mor Salomon at the Israel Cohen Institute for Biological Control. A female who sacrifices herself will be “providing more food than they can find by foraging for prey”.

Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2017.08.006

 

CSIR warns of major resurgence of Fall Armyworm pests

Source: Ghana | Myjoyonline.com
Date: 15-09-2017 Time: 05:09:45:am
 ghana aw

Scientists at the Council for Scientific and Industrial Research (CSIR) have warned there could be a major resurgence of the Fall Armyworm pests on farms across the country from next month.

Scientists at the country’s premier science and technology institution, therefore, want the government to immediately activate a fight back plan to avert destruction.

Fall Armyworms are pests that wreak havoc on crops if left to multiply.

The caterpillars mainly attack maize crops and eat everything in an area. Once the food supply is exhausted, the entire “army” will move to the next available food source.

Army worms -Akatsi2

Since March this year, the pests have invaded more than 115,000 hectares of farm fields leaving farmers struggling to recoup their investments.

The invasion appears to have died down as the major planting season ended last month.

Related: Fall armyworms have been defeated – Agric Minister

However, Entomologists at the Crop Research Institute of CSIR say the upcoming invasion could be worse than what farmers had to battle with a few months ago.

Dr. Kofi Frimpong Anin, an Entomologist at CSIR, said the pests are likely to strike stronger from next when a new farming season starts.

“Normally, after a major season, we have high residue of the pests in the system. So once you move into the minor season they strike and the infestation is worse compared to the major season.

“It is likely that we are going to have a worse season compared to the minor season if you don’t manage it well,” he told Joy News.

When Agric Minister, Dr. Akoto Owusu Afriyie appeared before Parliament last month to answer questions about the Armyworm invasion, he revealed that some 112,812 hectares of farmlands were affected by the fall army worm but only 14,430 hectares were destroyed.

He also indicated that the pests have been defeated, adding there is an ongoing research into biological control which will be implemented as a long term plan to rid the nation of the pest.

The Minister added that his team will create a strategic stock of chemicals in the regions and districts so control will be issued at any point in time there is another attack.

Again, farmer training he explained, is being intensified when it comes to the detection of the pest to avoid the recurring of the situation.

However, farmer unions have denounced the Minister’s declaration that the pests have been destroyed, accusing him of belittling the debilitating effects of the pests.

 

 

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GM diamondback moths

Hort week

“Self-limiting” diamondback moths trialled in US

An Oxford-based biotech firm has begun field trials of genetically modified (GM) diamondback moths that aim to control numbers of this damaging pest.

Image: Olaf Leillinger (CC-BY-SA-2.5)
Image: Olaf Leillinger (CC-BY-SA-2.5)

A non-native arrival to the US, the diamondback moth (Plutella xylostella) is the world’s most damaging agricultural pest of brassica crops, costing US farmers over $4 billion yearly in crop losses and control management. It also has a high level of resistance to conventional pesticides.

Instead the male GM moths, bred by US-owned Oxitec, pass on a self-limiting gene that prevents their female offspring from reaching adulthood.

The moths also have a fluorescent protein marker to distinguish them from wild pest moths, enabling their spread to be tracked.

The US government-approved field evaluation will be conducted at Cornell University’s New York State Agricultural Experiment Station, led by the university’s Professor Tony Shelton, an expert on sustainable agriculture.

“Importantly, this technology only targets this damaging pest species, and does not affect beneficial insects such as pollinators and biological control agents,” he said.

“Our previous greenhouse and field cage studies of this technology worked extremely well, and the evaluation will help us determine how well it works in the field.”

The earlier research was published in the journal BMC Biology.

Unusually large numbers of the moths were found in the UK last year, causing widespread damage to brassica crops.


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An adult male coconut rhinoceros beetle. Emmy Engasser, Hawaiian Scarab ID, USDA APHIS ITP, Bugwood.org

10 years ago the Coconut Rhinoceros beetle (CRB) was first discovered on the western Pacific island of Guam. Since then, these shoe-shine black, miniature invaders have spread to all parts of the island and are laying waste to the local coconut and oil palm population. The economy, culture and ecology  of Guam and other Pacific islands are intrinsically linked to the native palm species such that the rhino beetle poses a major threat. The indigenous peoples of Guam have a long history of weaving palm fronds, an artistry that is now at risk due to the rhino beetle. These trees are a symbol of tropic paradise, a motif that drives Guam’s primary industry; tourism.

The situation

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A Coconut palm damaged by CRB © Aubrey Moore

The principal method of rhinoceros beetle control is through the release of a virus specific to CRB known as Oryctes rhinoceros nudivirus (OrNV). As a biological control strategy, it has been highly effective at keeping CRB populations low and thus lessening palm damage by up to 90% (Bedford, 2013).

Up until Guam, 2007, it had been 40 years since an outbreak of CRB on an uninfested palm growing Pacific island, owing to the persistence of OrNV in beetle populations. Early attempts at disseminating the virus in the new Guam population proved surprisingly ineffective. Upon DNA analysis, the invading rhino beetles were found to be genetically distinct from CRB native to other Pacific regions. The Guam population was deemed a new biotype (CRB-Guam) and was found to be resistant to all available OrNV strains.

This resistance has proved paramount to the invasive ability of CRB. As well as Guam, the new biotype has now been logged in Papua New Guinea (2009), Palau (2014), Hawaii (2014) and the Solomon Islands (2015) (see figure 1). There is now a real threat of a Pacific-wide outbreak of CRB. Smaller islands, where traditional, palm-dependent economies still operate, stand to suffer the most.

CRBmap2
Figure 1: “The CRB-Guam biotype has invaded five Pacific Island countries and territories in only eight years compared to the CRB-Pacific biotype, which has not had geographical range expansion for 40 years

The passing of Typhoon Dolphin over Guam in 2015 highlighted the dangers of an event like this triggering rapid growth in CRB populations. Downed trees and vegetative waste make ideal breeding sites for the beetle. A positive feedback system may be initiated whereby more breeding sites allow for larger populations which kill mature palm trees which, in turn, become breeding sites for subsequent generations.

What can be done?

Numerous management techniques have been attempted on Guam since 2007. In March 2012, the Plantwise Knowledge bank reported on a promising new biological control method, the Metarhizium fungus. The fungus is specific to rhino beetles and the CRB-Guam biotype appeared susceptible to it. Unfortunately, it has not proved as effective as once thought and the Guam beetle population persists at damaging levels.

General sanitation practices that involve keeping areas free of green waste help to reduce the number of breeding sites, invariably limiting the potential for CRB population growth. However, this task proves tricky on a 210 square mile island covered in dense jungle and off-limits military bases.

Previously, specially trained detector dogs were used to root out rhino beetle breeding sites. This method, however, proved expensive and hard to reach areas were beyond its capability. More recently, new radio tracking technology has been proposed as a more cost-effective alternative. Small radio transmitters are glued to adult rhino beetles, these are then released and tracked back to previously unknown breeding sites. In August 2015, a 10-day field trial was carried out with some success.

As concern surrounding CRB mounts, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has announced funding worth $1.7 million, to go to Hawaii and Guam, with aims at combating the spread of this tenacious pest.

For Guam at least, complete eradication seems evermore unlikely. It appears the island’s best chance is population suppression and management. Aubrey Moore, an entomologist at the University of Guam, who has been working on CRB ever since it’s first appearances on the island, says that current work focuses on finding an OrNV isolate that the CRB-Guam biotype is susceptible to.

Jack Sayers is a Biological Sciences student at the University of Edinburgh, with a particular interest in genetics. He has spent his summers working for CABI as part of the Plantwise team.


References

Bedford, G. O. (2013) Long-term reduction in damage by rhinoceros beetle Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae: Dynastinae) to coconut palms at Oryctes Nudivirus release sites on Viti Levu, Fiji. African Journal of Agricultural Research 8(49) pp. 6422-6425

Marshall, S. D. G., Moore, A. and Vaqalo, M. (2016) A New Coconut Rhinoceros Beetle Biotype Threatens Coconut and Oil Palms in Southeast Asia and the Pacific. Western IPM Center.

 

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Citrus greening disease found in Trinidad and Tobago

Citrus Greening Disease has been confirmed in several parts of Trinidad and Tobago, according to the Ministry of Agriculture.
The disease also known as Citrus Huanglongbing (HLB) is caused by an insect-spread bacterial infection and affects all types of citrus.
A release from the Ministry said the disease has now been declared a reportable disease, making it mandatory that cases be reported to the Ministry.
The Ministry has now embarked upon a public awareness campaign, which has started in Tobago.
The campaign will include surveillance operations to determine levels of HLB pathogenicity in the island. Training in new nursery management protocols and best management practices for citrus greening will also be factored into this exercise, the Ministry stated.
Citrus Greening Disease presents the greatest threat to the citrus industry in Trinidad and Tobago, some 1,200 acres. HLB has devastated millions of citrus orchards in Asia, America and the Caribbean, notably Jamaica and Belize.
The disease reduces yields and compromises the flavor, color and the size of the citrus fruit before killing the citrus tree.

Publication date: 9/18/2017

west f p

Don Hopkins Matt Daugherty
University of Florida plant pathologist Don Hopkins surveys vines in University of California -Riverside test plots for symptoms of Pierce’s disease.

A new biocontrol shot protects wine grapes from Pierce’s disease

In an extensive series of lab studies and in field trials at vineyards in several states including those at the University of California – Riverside, this form of biocontrol has proven effective in preventing vines from developing the disease.

Greg Northcutt | Sep 13, 2017

Although Pierce’s disease has been a threat to California vineyards since at least the 1880s, when it wiped out 40,000 acres of wine grapes in the Los Angeles Basin, there’s still no cure for it. However, Don Hopkins, a University of Florida plant pathologist, has found a way to protect uninfected vines from the disease by giving them a shot of a benign strain of the same type of bacterium that causes it.

In an extensive series of lab studies and in field trials at vineyards in several states including those at the University of California – Riverside, this form of biocontrol has proven effective in preventing vines from developing the disease, Hopkins said.

 This benign bacterial strain is part of a broader class of control agents often referred to as symbiotic control. The strain was patented in 2009 by the University of Florida, which recently licensed it for commercial development.

 

In Florida, where vineyards have long faced heavy pressure from Pierce’s disease, Vitis vinifera grape vines typically die within about three or four years after becoming infected with the disease. However, one block of Cabernet Sauvignon in a Florida vineyard remains free of Pierce’s disease symptoms 15 years after Hopkins inoculated the vines with the benign strain of the pathogen.

The disease is caused by the bacterium, Xylella fastidiosa. Growing in the xylem, the water-conducting vessels of the vine, it can kill grape vines in as little as a year or two by blocking movement of the water.

The economic cost of Pierce’s disease to California’s grape growers began rising significantly in the early 1990s, not long after arrival of the invasive glassy-winged sharpshooter, likely as eggs on nursery stock from the southeastern United States. It’s one of several members from two groups of insects – sharpshooters and spittlebugs – which can spread the disease by feeding on the xylem sap.

The glassy-winged sharpshooter is the most threatening vector because of its ability to use a much greater diversity of host plants – more than 300 different types – than the others and to achieve much higher population densities.

The glassy-winged sharpshooter was first found in Orange and Ventura counties in 1989. Since then it has spread throughout southern California and into the central part of the state, including San Luis Obispo, Santa Barbara, Santa Clara and Tulare counties. Recently, after several years of effectively controlling the glassy-winged sharpshooter, growers in some areas of the state have seen populations of the pest beginning to resurge significantly.

Hopkins discovered the benign strain of Xylella fastidiosa in an elderberry bush as part of his initial research on the bacterium. During several years of lab testing in the early 1990s, he found that, by introducing this benign bacterial strain into very young vines and then exposing them to the pathogenic strain, most vines did not develop Pierce’s disease.

In the lab, Hopkins treated the very young vines by placing a drop of the benign bacterial suspension on the stems. Then, he punctured the vines with a needle, which allowed the bacteria to be taken up in the xylem. Two weeks later he used this approach to inject these same vines with the pathogenic strain. In most cases, the vines treated with the biocontrol did not show symptoms of Pierce’s disease.

Meanwhile, others vines, which did not receive the biocontrol treatment, were injected with the pathogen. Most of them later developed Pierce’s disease.

Hopkins then repeated these trials under actual field conditions in a Florida vineyard. “The biocontrol turned out to be more effective at preventing the disease in the vineyard than it was in the greenhouse,” Hopkins says.

Next followed vineyard trials involving a number of different wine grape varieties in Florida as well as in Georgia and California. Vines that were not inoculated with the benign strain of the bacterium often developed symptoms of Pierce’s disease in one to six months.

“Usually, in new plantings, we can see a difference in the health of treated and non-treated vines within from six months to three years,” Hopkins says.

Meanwhile, most of the inoculated vines remained free of the disease throughout the five- to six-year-length of the studies.

“We don’t know how this benign strain of the bacterium works to protect the vine,” he says. “Somehow it doesn’t allow the pathogen to build up in large enough numbers to block the xylem.”

Results of the UC-Riverside vineyard trials with Cabernet Sauvignon and Pinot Noir, which began in 2012, have been similar to those in Florida and Georgia.

“As of last year, we had not lost any treated vines to Pierce’s disease, and the growth, vigor and production of most of these vines remained really good,” Hopkins said. “However, several untreated vines died from the disease. Also, some of the treated vines were showing symptoms of the disease by the end of the trial. Either they didn’t get inoculated properly or the pathogen overcame the benign strain of the bacterium. But, that’s to be expected. As with any type of biocontrol, treatment is not 100 percent effective.”

Hopkins notes some of the other findings in this research:

  • Early on he and his colleagues noticed the benign bacterium doesn’t colonize young vines much past the 10th or 12th internode. The colony of the pathogenic strain, on the other hand, continues to advance through the plant as the vine grows. Still, the biocontrol induces resistance to Pierce’s disease beyond the area which it colonizes.
  • The benign strain of the bacterium multiplies at a much lower rate than the pathogenic strain. In fact, Hopkins notes, the population of the strain of benign bacterium in the vine is 100-fold smaller than the pathogenic strain and does not build up populations in the grape plant that will cause symptoms.

Hopkins says that, while this treatment can prevent most of the vineyard from becoming infected with Pierce’s disease, it won’t cure vines that have already been infected with it. “If a mature grape vine is coming down with Pierce’s disease, this biocontrol treatment is not going to prevent the disease from developing and, eventually, killing the vine,” he says.

While stress can make Pierce’s disease symptoms more severe, the benign strain has provided control compared to the untreated in all conditions, including drought, other diseases, and insect pressure.

Ideally, the best use of this benign bacterium would be to treat very young vines while they’re still in a greenhouse or transplant house before they are transplanted in the field, Hopkins says. Inoculating the small individual vines while on benches is much easier than in a vineyard. Plus, it minimizes the risk of newly planted vines from contracting Pierce’s disease before they are treated.

The ability of this benign form of the bacterium to protect vines for the long term are promising, he adds.

“Originally, we thought vines would have to be inoculated with the biocontrol every year or two for the treatment to remain effective,” Hopkins says. “But, we’ve been surprised. Some of the data indicate that one treatment might protect the vines for life. Normally, as long as a biocontrol strain survives, it continues to provide good protection. In this case, one treatment and, maybe, a booster later, should be enough to prevent infection with Pierce’s disease.”

Biocontrol of honeysuckle

Scoop

 

Honshu White Admiral versus Japanese Honeysuckle

Honshu White Admiral versus Japanese Honeysuckle

 

Greater Wellington’s biosecurity guardians get on top of most pest plants, but there are times when we have to enlist nature to help us tip the scales in our favour.

And so it is with the fight against the Japanese Honeysuckle, a highly invasive vine that climbs over and smothers most plants, causing canopy collapse and allowing the invasion of more species of weeds. It thrives in a variety of habitats such as shrub lands, forest margins, coastal areas, river systems and wetland margins and is widespread around our region.

Enter the Honshu White Admiral butterfly, a biocontrol agent Greater Wellington Regional Council hopes will stop its spread and bring the light back into woodland canopies.

The butterflies will be used in the front line of efforts to control Japanese Honeysuckle, providing a cost-effective, easy to manage approach to what is becoming in some areas a major challenge to the health of our bush.

“We released around 100 butterflies in April 2017 to control an infestation in the Akatarawa ranges,” says Greater WellingtonBiosecurity Officer (Pest Plants) s Kieran McLean. “The butterfly’s offspring, during their caterpillar stage, will eat their way through the plant’s foliage. If the numbers are large enough they can defoliate the honeysuckle without damaging the host plant. Hopefully the caterpillars are out there now eating their way through honeysuckle leaves.”

The black, white and brown butterfly us quite small: its wingspan is only 6cm. It lives for only one month but during that time lays around 200 eggs. As the caterpillars hibernate in cold weather, the Honshu white admiral is usually seen in warmer months.

Development from an egg to an adult butterfly can occur in as little as eight weeks at warm temperatures. Egg to caterpillar takes about one week. After about six weeks the caterpillar is fully grown and it then sheds its skin to form a light green and brown pupal case suspended from the plant. One week later it emerges as a butterfly.

Extensive research is undertaken before a biocontrol agent, such as the Honshu White Admiral Moth, is introduced. In New Zealand where biocontrol agents have been introduced follow up surveys have been undertaken to check for non-target damage.

So far Landcare Research has reported that 20 invertebrate agents and five fungal agents (including three self-introduced species) have been surveyed and results have provided additional assurance that current best practice host-testing is a good indicator of what will happen in the field. Non-target attack was generally absent, even when some might have been expected

It will take several years until we know if the population of butterflies has been successfully established and if they are effective at damaging the Japanese honeysuckle. Follow up research on their impact will take place this summer, though it will take several seasons to properly assess their performance.

Using biocontrol agents is just one of the ways Greater Wellington’s biosecurity officials work to keep the region free of pest plants and pest animals.