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Misconceptions about biological controls

June 24, 202188

By Ethan Proud
PREVIEW Columnist

For some, biological controls (biocontrols) seem like a silver bullet, capable of removing invasive species without using herbicides. To others, it seems counterintuitive to release a non-native species on an invasive species wreaking havoc on the ecosystem.

Biocontrols, unfortunately, do not eradicate a population, though there are some exceptions and populations can decrease by large margins when an insect herbivore is released into the environment. These biocontrol agents will suppress the population of invasive species and can help slow the spread, though they will not completely eradicate the noxious weed. 

Biocontrols must be released repeatedly to see success and a onetime release will not yield great results. Paired with chemical or mechanical control, an acceptable level of control can be achieved. Release biocontrols in areas that are difficult to reach with a backpack, ATV mounted sprayer or equipment for manual control. It’s easier to hike into a difficult area with a small container of insects than it is to carry a shovel and a bag — especially when the bag is completely full and it is time to hike out. Utilize mechanical and chemical control around the perimeter of the release site and you will have a one-two punch, biocontrols suppressing the heart of the infestation and chemical or mechanical control containing the spread.

When it comes to approving a new biocontrol agent, the insects must first be carefully studied through a round of choice and no-choice tests, where it is determined that A) the insect will feed on only the target species and B) the insect will starve to death before finding a new food source. These tests are conducted by the U.S. Department of Agriculture Animal and Plant Health Inspection Service Plant Protection and Quarantine Program, or USDA APHIS PPQ for short. The process of approval takes many years, meaning that new biocontrol agents are not only very exciting, but few and far between.

In short, biocontrol agents need to be paired with another control method to be truly effective and they are not an option for certain weeds. However, they are a great tool for integrated pest management and can reduce our dependency on herbicides.

For more information on biological control agents that can be released in Colorado and are available to landowners, visit the Colorado Department of Agriculture website and click Biocontrols underneath the Conservation Banner.

Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.

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Metabolic weed resistance theme of UT Weed Tour

Ginger RowseyLarrySteckelWeedTour.jpg

Larry Steckel, Extension weed scientist with the University of Tennessee shares information about his latest research during the 2021 Weed Tour.University research points to spreading metabolic weed resistance in Tennessee fields.

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The University of Tennessee held its annual Weed Tour on June 16 at the West Tennessee AgResearch and Education Center in Jackson. The overarching theme of the day — metabolic weed resistance is here and spreading.

“We’re clearly seeing metabolic resistance,” said Larry Steckel, UT Extension weed specialist. “It’s different than what we’ve always seen with target site resistance, which is what Roundup or PPO resistance was. With target site resistance, it seems like overnight, the herbicide, even applied at six to ten times the labeled rate quits working on a particular weed. While what we have seen with metabolic driven herbicide resistance typically involved more than one herbicide with the level of resistance two to four times.”https://a9ffbcfe2d577340816712d2d2a5ee6b.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

“We’re seeing it with dicamba and 2,4-D, but we’re also seeing more subtle declines in control with a number of different herbicides, including the Group 15 herbicides like Dual or Warrant,” he adds. “Not that they’re not working, but maybe they were working for 17 days and now they’re only holding 15-16 days.”

Steckel’s take home message for managing metabolic weed resistance: Use the max rate of pre-emergence herbicide for any given soil type. Then, overlay another pre-emergence herbicide. You’ll need two passes of post-emergence herbicides. Be as timely as you can with those post applications.

Visitors to the Weed Tour were able to see dozens of herbicide treatments in the university’s research plots. The tour was led by Steckel, along with Clay Perkins and graduate student Delaney Foster. In addition to plots at the AgResearch Center, Steckel and his crew conduct on-farm research where they are seeing more evidence of metabolic resistance. Even documenting Palmer amaranth escapes from applications of auxin herbicides made at the 4X rate.ADVERTISING

“We’ve got to start thinking about some different ways to manage for it,” he added. “One is to be as timely as possible, which is easier said than done. The other is relying more on pres. Based on my conversations with farmers and retailers, I think we’re using more pre’s this year, and I think that’s helped. They’ve worked for the most part pretty well. But now we’re in the crunch time when all the posts are going out, and I’m expecting some calls from folks who are disappointed in their herbicide performance.”

Combating metabolic weed resistance

Cytochrome P450 is a naturally occurring enzyme that detoxifies foreign chemicals. It’s found in plants and animals, but plants have more genes for the P450 enzyme. Over time growers inadvertently select for weeds with higher numbers of these enzymes in their genetic makeup. These enzymes can then detoxify herbicides applied to the weed.

Researchers often test for metabolic resistance by mixing the herbicide in question with malathion. Malathion, along with all the organophosphate insecticides, are known cytochrome P450 inhibitors. That means they’ll bind up the enzyme that is detoxifying the herbicide.

“When you inhibit those P450’s, the thought is the herbicide will now kill the weed,” Foster said.

Steckel and Foster were hopeful malathion could be a solution. In greenhouse research this past winter, they saw promising results, with malathion improving auxin herbicide control as much as 32% in some treatments. But results in field trials were not as good.

“It worked a little better with 2,4-D than dicamba,” Foster said, “but here we didn’t see a big malathion difference. That doesn’t mean this herbicide resistance isn’t metabolism based. There are hundreds of P450 enzymes and lots of P450 inhibitors. Malathion targets one. We’ll continue evaluating other P450 inhibitors and hopefully figure out what the mechanism of resistance is here.”TAGS: CROPS

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Ceylon Daily News

Plans to produce powerful natural herbicide using invasive species

Saturday, June 19, 2021 – 01:16Print EditionLocal

The Environment Ministry plans to produce a powerful natural herbicide using several invasive species that are to be removed from the environment immediately in support of the President’s organic farming programme.

The purpose of this is to prevent the use of chemical pesticides and herbicides along with the ban on the use of chemical fertilizers and to prevent farmers from getting into trouble due to the lack of a suitable herbicide for weed control.

Environment Minister Mahinda Amaraweera instructed Ministry officials on Thursday to be prepared to make a special contribution to the promotion of organic farming under the Ministry.

The discussion was attended by Ministry Secretary Dr. Anil Jasinghe and heads of the Central Environmental Authority, Geological Survey and Mines Bureau, Technical Services Company and many other external institutions.ht

“The decision taken by the President to stop the use of chemical fertilizers for cultivation and to introduce organic farming instead is a historic decision. Other Ministries cannot remain silent, leaving these matters to the Ministry of Agriculture alone. Therefore, as the Ministry of Environment, we have a great responsibility to intervene in this matter,” said Minister Amaraweera.

“Farmers are currently demanding chemical fertilizers. The decision taken by the President for organic farming will be implemented from this Maha season. Therefore, there is a need to provide chemical fertilizers during the Yala season this year. It was also proposed to set up a medium scale factory for this purpose in the Hambantota District where these invasive plants are in abundance,” the Minister said.

“Pesticides and herbicides along with chemical fertilizers have also been banned, making it difficult for farmers as well as cultivators to get sufficient manpower in the tea and rubber industry as well as in paddy cultivation. There is a possibility of producing a successful herbicide using these invasive plants as a solution. It is also 100% chemical free and eco-friendly. Arrangements have been made to hold further discussions in this regard at the Divisional Secretariat in Hambantota today (19). These invasive plants are species recommended by the Ministry of Environment for immediate destruction,” Minister Amaraweera said.

The Minister also said that steps will be taken to launch a number of small and medium scale projects for the

production of organic fertilizer required for agriculture in the Hambantota District during the Maha season this year.

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University of Massachusetts Amherst

Reactive and inconsistent practices hamstring efforts to manage invasive plants in the US

New research from UMass Amherst suggests that communication is the key to success

23-Jun-2021 1:25 PM EDT, by University of Massachusetts Amherstfavorite_border

Newswise — AMHERST, Mass. – As summer unfolds, more than 500 species of invasive plants will be taking root in fields, lawns, and gardens across the US. As plants continue to move north driven by climate change, the number of invasives will only increase. Unfortunately, inconsistent regulations that vary from state to state means that invasive plants have an edge on our attempts to control them. However, new research from the University of Massachusetts Amherst recently published in the Journal of Applied Ecology suggests that we already have an answer in hand – communication.

“We know that invasive plants are causing both ecological and economic harm in the US,” says Emily Fusco, one of the paper’s lead authors and a postdoctoral research fellow in the department of environmental conservation at UMass. One of the best tools that invasive-species managers have are prohibited plant lists, which are compiled and maintained by state and county-level officials to prevent intentional introductions of known invasive and weedy plants. Unfortunately, a lack of overall coordination lends a patchwork quality to efforts to control invasive plants.

The study’s authors found that states in the lower 48 have listed anywhere between zero invasive plants and 162. Even worse, contiguous states often regulate very different sets of species: on average, only 20% of the plants listed as invasive in one state will show up on their neighbors’ lists. Finally, states are failing to get ahead of emerging invasive plants: 90% of the time states only list a plant as invasive once it has already become present in their state, making it more difficult to eradicate. “We’re missing an opportunity to prevent invasions before the species are widespread,” says Fusco. “These prohibited plant lists are one of the most useful tools we have for preventing plant invasions, but our work shows that states are not creating these lists in a proactive way.”

Yet, there’s a bright side to all this: “It’s not that the states are doing a bad job,” says Evelyn Beaury, the paper’s other lead author and a graduate student in organismic and evolutionary biology at UMass. “We don’t need to reinvent the wheel – we just need to have more conversations about what happens across state borders. We need to give managers the infrastructure and resources to work together.”

In fact, such work is already happening at the Northeast RISCC Network. RISCC (Regional Invasive Species and Climate Change) is a coalition of invasive species managers from throughout the Northeast who work with researchers and each other to identify and respond to new threats posed by invasives in a changing climate. “State officials want to improve coordination and share resources across borders,” says Bethany Bradley, senior author and professor of environmental conservation at UMass. Bradley is also one of the cofounders of RISCC and says that the invasive species managers she works with through the network “are thrilled to have more ways to exchange information.”

“We have a real chance to get ahead of the climate change/invasive species curve,” says Beaury. “We need to get more people on board and that begins with starting conversations that cross state borders.”

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Robots may be suited to help kill weeds in strawberry fields

Through new research, University of Florida scientists Boyd and Schumann hope to eventually help strawberry growers combat weeds. Additionally, robots may replace tractors as the means for delivering the spray in the field. Getting rid of weeds is critical for growers in Florida’s $300 million-a-year strawberry industry.

The UF/IFAS researchers mount a smart spray system to a tractor-pulled sprayer, which uses the highly targeted process to spray only weeds. So far, they’re killing up to 90% of the weeds. Precise spraying depends on many factors, including the types of weeds that scientists target and the speed of the tractor that sprays the weeds, Boyd, a UF/IFAS associate professor of horticultural sciences, told tampafp.com.

While the research remains in the preliminary stages, Boyd wants to reduce the amount of herbicide spray strawberry growers use. That saves farmers money and helps cut unwanted chemicals from getting into the environment.

Asked for cost-savings estimates, Boyd gave this example: If you shoot low and anticipate a grower using an inexpensive herbicide that costs $30 per acre and you drop the amount of spray by 50%, you save $15 per acre.

Photo source: UF/IFAS 

Publication date: Fri 11 Jun 2021

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food tank

Virginia Tech Research Explores Climate Change and the Future of Food in Nepal

When you think of Nepal, you might imagine people climbing Mount Everest, the world’s highest mountain above sea level. However, people aren’t the only ones scaling the vast and varied elevations of the Southeast Asian country—so are invasive weeds.

Recent research from the U.S. Agency for International Development (USAID)-funded Feed the Future Innovation Lab for Integrated Pest Management (IPM Innovation Lab) shows that invasive weeds have rapidly spread over time in Nepal. One of the major push factors of this spread is climate change. As Nepal’s temperature is projected to increase significantly in the next 50 years, invasive species are spreading more rapidly, which puts at risk crop production, livelihoods, biodiversity, and food security.

“The basis of our research includes looking at how invasive weeds spread along elevations under past and current climate scenarios,” said Pramod K. Jha, Professor Emeritus at Tribhuvan University in Nepal, which implements the project locally. “We use satellite images to capture these changes throughout the Chitwan Annapurna Landscape in central Nepal. Making observations about how our land changes over time is crucial for identifying vulnerable areas and developing strategies to address them.”

Jha noted that of the seven invasive weeds the project tracks, all but one has dramatically increased in spread over the last 30 years—and they will continue to spread if no mitigation efforts are made.

One of those weeds, for example, is Parthenium hysterophorus. Under future climate scenarios, its range is expected to expand significantly in all regions of the Chitwan Annapurna Landscape (CHAL). The weed, native to the New World, causes human health issues such as rashes and respiratory difficulty, taints livestock milk, and disrupts valuable farmland. With the weed’s habitat suitability projected to expand into protected areas including Langtang National Park, Annapurna Conservation Area, and Manaslu Conservation Area, valuable biodiversity is at stake.

Ageratina adenophora, also known as Crofton weed, is another invasive species the program studies. Crofton weed reduces crop yields, displaces native plants, and affects the carrying capacity of grazing lands. Under future climate scenarios, the program has predicted the weed will expand its elevational range and all regions except the Middle Mountain region are expected to gain suitable areas in which the weed will expand its reach.

Invasive species are capable of quickly adapting to climatic changes, hence their ability to push native species out. Muni Muniappan, Director of the IPM Innovation Lab, said that central Nepal’s ecological richness—unique biodiversity hotspots and topography, subtropical to alpine climates, elevations that range from 200-8091m above sea level—is both what makes it an ideal place to study climate change impacts as well as what puts it most at risk of climate change impacts.

“All of the invasive weeds this program studies are originally sub-tropical and tropical in nature,” Muniappan said, “so they initially invaded tropical zones of Nepal, such as the lowlands. Now, however, we are seeing them gradually spread to new habitats, like the mountains. This is especially detrimental because the mountains house some of the most resource-poor communities in Nepal. These communities heavily rely on natural resources, so these consequences of climate change will have a disproportionate impact.”

One of those threatened resources is finger millet, Nepal’s fourth most important crop. Considered a “poor man’s crop,” remote mountain communities of the country depend on finger millet because it can grow in rain-fed, subsistence farming conditions. Communities also rely on it as an important source of protein, fiber, calcium, and iron. The Virginia Tech-Tribhuvan University program measured that nearly 40 percent of area of Nepal is highly suitable for finger millet, but under future climatic conditions, where invasive weeds will be more widespread, the suitable area of finger millet would shrink by 4 to almost 9 percent in 2050 and nearly 9 to 10.5 percent by 2070. Because of the climate crisis and its resulting impacts, mountain communities that rely on this crop may be in even greater danger of food insecurity.

As climate change persists, developing countries stand to lose the most from its impacts, including the rampant spread of invasive species. Among 124 countries, Nepal has the third highest threat to agriculture sectors from invasive species spread. While the IPM Innovation Lab measures invasive species spread, it also aims to improve resiliency against them. One such approach is implementation of “IPM packages,” or suites of holistic techniques farmers can choose from to address crop threats. Application of biocontrol, for example, is one IPM package component that could safely and economically mitigate the spread of the invasive Parthenium weed.

“Sustainably addressing climate change and its impacts remains a top priority of the IPM Innovation Lab,” said Muniappan. “Through modeling invasive species spread, we gain early knowledge on their projected pathways, but this information also gives us valuable insight for designing the most productive measures for managing their spread. This is only the beginning – an important aspect of this work is garnering the interest of other institutes, organizations, and universities as well. Fighting climate change and its impacts requires a united effort.”

The Feed the Future Innovation Lab for Integrated Pest Management currently works in seven countries in Asia and Africa on a range of topics, including improving food security, increasing farmer income, gender equality in development, among others. Since its inception in 1993, it has been housed at Virginia Tech’s Center for International Research, Education, and Development.TweetShareShare

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Sara Hendery
Sara Hendery

 Sara Hendery is a Communications Coordinator for the USAID-funded Feed the Future Innovation Lab for Integrated Pest Management and the Center for International Research, Education, and Development, both housed at Virginia Tech. Hendery earned a BFA in English and Creative Writing from UNC Wilmington and an MFA in Nonfiction Writing from Columbia College Chicago.

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euronews.com

A race against time: The giant weeds taking over Lake Ossa in Cameroon

Lake Ossa, Cameroon

Lake Ossa, Cameroon   –   Copyright  AMMCOBy Nalova Akua  •  Updated: 12/05/2021

Cameroon’s coastal waters have been invaded by three of the world’s most dangerous water weeds, proving an existential threat to aquatic ecosystems and livelihoods of riparian communities.

The latest of these weeds, Salvinia molesta, is a free-floating, green-brown freshwater fern with branching horizontal stems. It has already invaded more than 40 per cent of Lake Ossa (4,000 hectares), the largest natural lake found on Cameroon’s coast, since 2016.

The weed doubles in size every 10 days.ADVERTISING

The other two, water lettuce and water hyacinth, appeared much earlier – in 1949 and 1970 respectively, according to the Cameroon National Herbarium, a collection centre for plant specimens.

As a flowering invasive aquatic plant, water hyacinth now covers 85 per cent of River Fiko and half of the Wouri River Basin – all water bodies found in Cameroon’s Littoral Region. Mats of this invasive weed double in size in five days.about:blank

The perennial evergreen floating plant known as water lettuce.htm) is found in patches on the surfaces of the Wouri River Basin and the lower reaches of the Sanaga River.

“Water lettuce doubles its biomass in just over five days; triples it in 10 days, quadruples in 20 days and has its original biomass multiplied by a factor of 9 in less than one month,” says Dr. Kenfack Voukeng Sonia Nadège, a Cameroonian weed scientist working with Green Connection, a local environmental conservation non-governmental organisation.

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“As floating weeds, they form dense mats on the surface of water bodies, disrupting aquatic flora and fauna underneath and thus adversely affecting the water ecosystem,” Dr. Kenfack adds.

“This hinders water flow, fishing, swimming, boating, water sports and navigation.”

All these invasive species are native to southeastern Brazil and northern Argentina but can be dispersed within an aquatic system by wind in the dissemination of spores; water currents, floods, and animals; as well as through human activities such as transportation by boat or canoe.

Uncontrolled industrial activities also favour the spread of invasive weeds in Cameroon’s coastal waters.

Pollution due to human activities favours the development of these plants.

Dr Kenfack 

“Being the economic capital, the Littoral Region and especially Douala is the most industrialised municipality in Cameroon with about 60 per cent of the country’s industries’ discharges often released in the open spaces,” says Kenfack.

“Besides, houses built without proper flushing systems contribute to the increase of the nutrients in the environment. Pollution due to human activities favours the development of these plants,” she says.

Canva
Salvinia molesta infests lakes and riversCanva

Dr. Kamla Takoukam Kamla, founder of the African Marine Mammal Conservation Organisation (AMMCO), agrees that poor land use triggers the proliferation of invasive aquatic weeds in Cameroon’s coastal regions given that the water columns are enriched with nutrients.

“Two main nutrients needed for invasive weeds to grow are nitrogen and phosphorous coming from upstream. Lake Ossa and the Sanaga River (the largest River in Cameroon) are connected by a 3km channel. Once this river gets polluted, the lake also gets polluted,” explains Kamla.

“It is possible that the nutrients are coming from the industries, plantations and hydroelectric dam reservoirs that are constructed upstream.”

A threat to the livelihood of humans and protected species

The Lake Ossa complex which contains three main lakes and over twenty islands is located in Dizangue, Littoral Region of Cameroon. In 1974, the complex was designated a faunal reserve and since 2018, has been serving as a National Park.

Before the Salvinia invasion, fishing was the major source of livelihood for over 80 per cent of the local population according to Global Water Partnership.

The lake was also an important habitat for many wildlife species including manatees, freshwater turtles, crocodiles, monitor lizards, snakes, aquatic birds and over 18 families of fish.

Before the Salvinia invasion, fishing was the major source of livelihood for over 80 per cent of the local population.

“The mats [of aquatic weeds] indirectly deplete dissolved oxygen, thereby asphyxiating and killing native fish and phytoplankton. With reduced fish supply, human nutrition in riverine communities where fish are the primary source of protein is jeopardized, leading to poor health,” explains Kenfack.

These invasive species “can rapidly out-compete native species and dominate the ecosystem, consequently reducing biodiversity by their exponential proliferation, depriving in return the native species of space, nutrients and moisture,” she adds.

AMMCO
Lake Ossa over the years, as the infestation has become worse.AMMCO

This results in a modification of the entire structure and functioning of the ecosystems.

The International Union for the Conservation of Nature (IUCN) has described the threat posed by Salvinia molesta to Lake Ossa and its ecosystem as “a conservation emergency.” At least 400 fishermen used to fish in Lake Ossa – fish being the main protein source for a couple of thousand people who live around the lake.

“In the past, I was able to make between 15 and 21 Euros daily as profit from selling fish. But today, I can barely make 6 Euros a day as profit,” says Dina Marie-Louise, a 51-year-old who has been selling fish caught in the lake for the past 22 years.

The lake was also an important habitat for wildlife species including manatees, freshwater turtles, crocodiles, monitor lizards, snakes, aquatic birds and over 18 families of fish.

The mother of 12 said the Salvinia attack on Lake Ossa – their main source of livelihood for generations – has shattered her plans of building a house for her family. Seven of her children have dropped out of school for want of means.

Kouoh Elinga Charles, 56, who has spent 30 years fishing in the lake, expressed the same concern adding that he has resorted to odd jobs to feed his polygamous home.

“The salvinia plant has disrupted fishing considerably,” he says.

Canva
Manatees used to live in Lake OssaCanva

“Initially I was able to save 15.32 euros from fishing daily. But today, it is difficult to fetch 1.53 euros from the activity which can hardly satisfy our household needs,” the father of eight said.

Water hyacinth and Salvinia invasions have also disrupted fishing and sand extraction in the Wouri River Basin and in the River Fiko – other main sources of income to the riparian communities.

Lake Ossa used to harbour a minimum of 50 individual African manatees, the least-studied of the three manatee species in genus Trichechidae. But their number is on the decline owing to the Salvinia attack on the lake. Manatees are large, slow-moving mammals that frequent coastal waters and rivers. They never leave the water but, like all marine mammals, manatees must surface about every five minutes to breathe.

When carpets of invasive weeds lock the surface of the lake, they prevent the African manatee from surfacing and breathing.

Dr Kamla 

“When carpets of invasive weeds lock the surface of the lake, they prevent the African manatee from surfacing and breathing. Consequently, they will likely leave Lake Ossa or move to another part of the lake not yet invaded by aquatic weeds,” Kamla said.

“If nothing is done, the lake will be completely invaded and there will be no fish, no manatees and no freshwater turtles which the lake is endowed with.”

Invasive species are considered the third most dangerous factor threatening world biodiversity, after habitat loss and over-exploitation, according to the International Union for the Conservation of Nature.

Can insects solve the problem?

To counter the spread of aquatic weeds in Cameroon’s coastal waters, the African Marine Mammal Conservation Organisation has partnered with similar international organisations and are considering the three existing approaches: manual removal, biological control and the integrated weed management control method.

The Integrated Weed Management (IWM) method entails combining multiple weed control systems into a single weed management programme, to contain the spread of a particular water weed according to Kenfack.

“Up to now, biological control offers a better opportunity to control the spread of these weeds, as compared to the other methods of control such as the chemical that could be dangerous to human and environment and the manual removal which is a very tedious process.

“Biological control uses host specific insects [Salvinia weevil in case of Salvinia molesta attack] which can only complete their life cycles on the target species to reduce the target plant populations. The insects are the plant’s natural enemies,” Kenfack said.

Salvinia weevils are small beetles which can eat the invasive weeds.

The first releases of the Salvinia weevil as a biological agent were at Lake Moondarra, Mount Isa, Australia in 1980.

AMMCO
The Salvinia weevil is a small beetle which can eat the invasive weeds.AMMCO

“Adults and larvae both feed on these floating ferns,” says Matthew Purcell, Director, USDA ARS Australian Biological Control Laboratory – a structure jointly operated by the Agriculture Research Service of the U.S. Department of Agriculture and the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

“The effectiveness varies from site to site depending on environmental parameters, temperature, nutrient availability and water flow, shade, etc.

“The larvae initially feed on roots, then move to the buds, finally tunneling into the Rhizome which can kill the plant; adults feed on all plant parts externally,” adds Purcell.

Scientists say biological control is globally considered as one of the most cost-effective, environmentally friendly and sustainable ways of reducing the impacts of invasive species.

Nearly 6,000 individual Salvinia weevils are being mass-reared in a facility in Lake Ossa by AMMCO.

“They were brought in from the Louisiana State University in the United States with the authorization of the Cameroon government,” says Kamla.

Scientists say biological control is globally considered as one of the most cost-effective, environmentally friendly and sustainable ways of reducing the impacts of invasive species.

“We keep mass-rearing them until we receive authorisation from the government to release them into the areas affected by water weeds. We are now conducting an experiment to know how long it will take for the weevils to get rid of these aquatic weeds in lake Ossa.”

An effective biological control of Salvinia molesta by using the Salvinia weevil was also applied in the Senegal River in the early 2000s. Similarly, the release of the weevil into South Africa’s fresh water systems in 1985 successfully brought Salvinia molesta under control.

“For water hyacinth, biological control entails the deployment of the weevils Neochetina eichhorniae and N. bruchi which are among the first to be used worldwide in more than 32 countries to control the weed,’’ explains Kenfack.

“They were found in some sites in the Wouri Basin causing damage on the mats of water hyacinth. However, their population is still small and must be mass-reared to obtain effective control of this plant (no need of an import permit).” The biological control agent of water lettuce is different though, she stresses.

Nalova Akua
Locals want Lake Ossa to be clear once again, so that their livelihoods can resume and wildlife can be saved.Nalova Akua

Neohydronomus affinis was used successfully in countries such as Senegal, Benin, Congo, Cote d’Ivoire and South Africa.”

Scientists have expressed hope that Cameroon may just be the next country for the successful implementation of biological control to weed out invasive water weeds.

“Because Cameroon is tropical, the prospects for successful biological control are high. I would predict that there will be a significant reduction in cover within 18 months, if not less,” says Julie Coetzee, Deputy Director and Manager of the Aquatic Weed Biocontrol Programme at Rhodes University, South Africa.

“While the process is not perceived as quick, in comparison to herbicide, it is sustainable in the long term. Patience is key,” she adds.

But Dr. Kenfack is concerned Cameroon may be racing against time.

“Limited progress [to mass-rear and authorise release of weevils] means the watercourses (Lake Ossa, Wouri Basin and Fiko just to name those) and all their biodiversity will be negatively affected.

“This calls for an urgent action in order to reap the benefits from these watercourses not only for us, but for the future generation,” she concludes.

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HOME>CROPS>WEEDS

They said weed science was dying, but then things changed

TAGS: HERBICIDERESISTANCE MANAGEMENTCOTTON GINSSOYBEANSJohn HartJohn_Hart_Farm_Press_Wes_Everman_Weeds.jpgWes Everman has been the Extension weed specialist for soybeans and small grains for 10 years. He has been on the job since 2011.At the time, Roundup Ready herbicides were taking over the world.

John Hart | Apr 26, 2021

Farm Progress Show 2021

Back in 2002, when Wes Everman was planning to pursue a Ph.D. in weed science, a number of professors discouraged him. They told him it was a dying field and that he would have a tough time landing a job come graduation.

At the time, Roundup Ready herbicides were taking over the world. Everman notes that one professor didn’t want to write a letter of recommendation for him to pursue a Ph. D because he saw no future in weed science.

Everman had just completed his master’s degree in weed science at Purdue University in 2002. He earlier earned his B.S. degree in Agronomic Business and Marketing from Purdue in 2000. Everman grew up on a farm in northeastern Iowa near Decorah. Everman’s grandfather ran the farm while his father was a local custom butcher.

For college, Everman said he bucked the trend and decided to go to Purdue instead of Iowa State University. As a boy, Everman had a passion for animals and could tell you all the breeds of hogs, cows, and chickens. He had originally planned to go into agricultural economics and pursue a career working with animals.

“I got into agronomy by accident. This was before the internet. Purdue sent out a brochure. One of the majors was agronomic business and marketing. I didn’t know what agronomy was. I thought agronomics was a clever play on agricultural economics: Agronomics. That sounded perfect so I checked the box on the brochure and sent it back,” Everman says.

When it came time for freshman orientation at Purdue the summer after high school graduation, Everman soon discovered he would be taking agronomy classes. “Where are all the business classes?” Everman wondered. 

Well, Everman’s adviser, Dr. Lee Schweitzer, encouraged him to stay in the program and said he could take business electives. Purdue is known for its good soil science program. At the time, Everman said he could care less about soils, but figured he was in college to learn things he knew nothing about, so he decided to stick with it.

Glyphosate dominant

Everman soon developed a passion for weed science research and decided to go on and earn his master’s and Ph.D. with the goal of working in research and Extension. However, a number of folks discouraged him because of glyphosate’s dominance in weed control across the country.

“Most people thought Roundup was the answer to everything. They believed all the other herbicides would be going away and it was all going to be Roundup. Glyphosate resistant horseweed did show up in 2000, but it wasn’t a terrible problem and it wasn’t across the country. It wasn’t until 2005 and 2006 when we started seeing glyphosate resistant Palmer amaranth,” Everman explains.

In fact, Everman explains that many good weed scientists who had just earned Ph.Ds. in 2004, 2005, 2006 and 2007 did indeed have a tough time finding jobs because many universities were not filling weed science positions.

It turns out glyphosate resistance as well as resistance to other herbicides would indeed become a major issue beginning in the late 2000s. And now in 2021, the problem isn’t expected to go away anytime soon. It turns out Everman was spot on in his decision to pursue a career in weed science. “Some people said I had good foresight. I was actually just stubborn,” Everman says with a laugh.

Everman was accepted into the weed science program at North Carolina State University. “I was told if I really wanted to learn about weeds, I needed to go to the South where there really are weed problems. I learned there are a lot more weed issues down here than in the Midwest,” he says.

Everman completed his Ph.D. at North Carolina State in 2008. His thesis was using Liberty Link and Liberty Link crops for managing Palmer amaranth and other troublesome weeds. Upon graduation, he did indeed land a job as an Extension weed specialist at Michigan State University.

Return to Carolina

In 2011, a weed science position opened up at his alma mater, North Carolina State University, so Everman decided to apply and landed the position. There were budget cuts and uncertainty at Michigan State so Everman knew the time was right to return to North Carolina.

He’s been on the job for 10 years now and has no regrets about working in weed science and working in North Carolina. “This is right where I belong,” he says.

Everman says he has a passion for helping farmers solve their toughest weed problems. Everman is the Extension weed specialist for soybeans and small grains.

In Extension talks and field days, Everman has continually emphasized the challenges of herbicide resistance, encouraging farmers to use multiple modes of action and cultural practices such a cover crops in their weed control regiment.

In North Carolina, there has been confirmed “three way” resistance of common ragweed to glyphosate, PPOs, and ALS inhibitors. There is also expected Palmer amaranth resistance to PPOs in North Carolina, which still needs to be confirmed. Glyphosate resistant ryegrass has been confirmed in North Carolina.

Everman explains that all the herbicide resistance is a culmination of years of use.

“I feel like where we are now, if we use a single mode of action heavily, we will probably get about five years out of it because the large seed bank is aiding in the development of resistance. We selected for weeds that have an ability to adapt to different stressors,” Everman explains.

“Some biotypes have enhanced metabolism so that when a herbicide is used, that enhanced metabolic pathway can break it down. Some of the resistant biotypes out there will even survive applications of sprays they’ve never been exposed to before. They have a mechanism now that allows them to survive just about anything. Where do we go?”

One great hope is harvest weed seed control or seed mills that have found success in Australia. North Carolina is part of a nationwide grant beginning this year where Redekop and Harrington Seed Destructors will be tested to see if they can be effectively used here as they are in Australia. Everman has already lined up two farmers in North Carolina to try the system on their operations this year.

“I’m hoping we get widespread adoption before we lose chemicals. Reducing the seedbank is one of the best ways. If we can integrate harvest weed seed control, we can reduce the seeds going into the soil and reduce the seed bank. Ultimately you have fewer weeds coming up in those fields and you have less selection pressure on your herbicides,” Everman says.

Everman stresses that chemical control of weeds isn’t going away anytime soon, but additional tools such as harvest weed seed control should have a place. He is really hopeful the system will work in North Carolina.

One thing is certain, Everman believes he made the right decision when he decided to pursue a career in weed science research and Extension. He notes that weeds are genetically programmed to survive which means there will a need to find news ways to control them.

In fact, Everman encourages others to pursue a career in weed science. “There will always be work that needs to get done,” he says.

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Combine old with new for resistant weed management

TAGS: HERBICIDEHERBICIDE RESISTANT WEEDSAdam Hixon, BASFadam-hixson-pigweed-glyphosate.jpgSignificant pigweed infestation remains in this field after two applications of glyphosate.Getting back to the basics is critical to managing herbicide resistant weeds.

Ron Smith | Apr 19, 2021

Weeds resistant to herbicides are a way of life for farmers, one more concern to complicate an already complex production system.

But options exist not only to manage resistance but also to reduce the size of the weed seed bank.https://82ae8ac4f4c5904dfe4704d0077ebf4f.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

“Resistance is here to stay,” said Adam Hixson, BASF technical service representative for Texas, Oklahoma, and New Mexico, during a recent media update on managing herbicide resistant weeds in the Southwest.

swfp-shelley-huguley-adam-hixon-profile.jpgAdam Hixson, BASF technical service representative for Texas, Oklahoma, and New Mexico. (Photo by Shelley E. Huguley)

“We’ve heard the expression, ‘out with the old and in with the new,’” Hixson said. “I want to change that to ‘in with the old and in with the new.’”

Back to basics

Getting back to basics, he said, is crucial to managing herbicide resistant weeds. He called on Texas A&M AgriLife Professor and Extension Weed Specialist Pete Dotray to put the problem in perspective.

“According to the International Survey of Herbicide Resistant Weeds, we have eight resistant weed species in Texas,” Dotray said. “The first case of resistance in the state was noted 30 years ago, but in the last 10 years, glyphosate resistance has created a lot of concern.”

Dotray said Roundup resistant Palmer amaranth, also known as pigweed and carelessweed, was first identified on the Texas High Plains about 10 years ago, later than in some Mid-South and Southeastern states. He believes a key to that late arrival was that High Plains farmers never abandoned residual herbicides, especially the yellow herbicides like Treflan and Prowl.

shelley-huguley-dotray-profile.jpgTexas A&M AgriLife Professor and Extension Weed Specialist Pete Dotray (Photo by Shelley E.Huguley)

Overuse of Roundup, using the same chemistry over and over, and use of fewer herbicide and tillage inputs provided an open door for the increase in resistant weed populations, Dotray said. “Resistant weeds were likely already out there in extremely low numbers.”

Palmer amaranth resistance has complicated weed management, Hixson added. “We’ve seen multiple applications of glyphosate at labeled rates fail to control Palmer amaranth.”

He said remedies include manual control, such as hoeing, which is expensive and time-consuming. “Also, we’re always looking for that next ‘shiny object’ that will solve the problem.”

Shiny things have been scarce in recent years, however, so Hixson offers a different option. “We need to use what we have today, but use it in a more calculated, knowledge-based approach. We have to get back to the fundamentals of weed control.”

Year-round effort

He and Dotray agree that successful weed control strategies do not focus solely on in-season herbicide applications. “Good weed management has to be a well-planned, year-round venture,” Hixson said.

Weed identification is a priority. “It’s important to identify the weeds and to understand fully the biology. Know when specific weed species are most vulnerable.”

He explained that Kochia, sometimes “a huge problem and resistant to several herbicides,” emerges early in the spring and typically has only one flush. An effective residual herbicide, applied at the right time, will take care of most Kochia issues.

Palmer amaranth, however, emerges from early in the season well into fall and requires a season-long management program.

Dotray said Palmer seed that emerge late in the season remain a threat to replenish the seed bank and create problems for the next crop year.

“We’ve looked at the abundance of seed one plant can produce,” he said. “Palmer that emerges early produces as many as 500,000 to 600,000 seed, maybe more, per plant. That’s a lot of seed. But a Palmer plant that emerges in August will still produce as many as 20,000 seed, also a lot. As late as September, emerging plants will produce 2,000 seed, and still hundreds by October. Even plants that emerge as late as November can produce some viable seeds.”

“Leaving just one plant,” Hixson said, “may add to the weed seed bank, a key factor for the next season. One seed per square inch represents more than 6 million seeds per acre.” So, next season’s weed control should start before this season ends.

Good news

Dotray said recent research shows a bit of good news about the longevity of Palmer seed. Studies have shown that some weed seed will retain viability for as long as 120 years.

“We had no good answer for how long Palmer seed remain viable, so five years ago we set up a test to see. We buried Palmer seed at various depths across the state.”

They uncover them at intervals, beginning at six months, again at 12 months, and yearly after that. Based on data from the first 48 months of the research, “Palmer seed viability begins to decline significantly after 12 months. Those findings were the same across all locations and at all depths. A second study initiated in 2018 has shown the same results so far,” Dotray said.

“The good news is that a farmer who does a good job of managing Palmer amaranth effectively with a systematic program can get them down to a manageable level in a short time.”

That system should include late applications to prevent escapes, he said.

Knowledge is key

Hixson said an effective weed management program also depends on knowing not only the weed species vulnerabilities but also the interactions of soils and chemistry.

He said using herbicides with multiple, effective modes of action should be a critical part of weed management

“But also understand the properties of the herbicides and how they respond to different conditions, including soil types and moisture. Soil leaching properties will affect herbicide efficacy,” he said. “Also, the more water soluble a product is, the deeper it will move into the soil profile. Less soluble usually means more soil binding.”

He said different soil types — changes in clay content, sand, organic matter level — all may affect herbicide activity.

He said in situations with good moisture, a product like Zidua could be the best option. “In dryland or subsurface drip irrigation conditions, Outlook would be ideal.”Adam Hixon, BASFadam-hixson-timely-applications.jpg

Timely applications, with overlapping residuals (Prowl H2O herbicide followed by Outlook herbicide), along with an effective postemergence herbicide (Engenia herbicide), provide exceptional control of Palmer amaranth.

They key is understanding the weed, the environment, and the herbicide properties, then using the proper material for the target weed under those specific conditions.

Timing and coverage

He added that application timing and coverage also matter.

“Also remember, the cottonseed trait package you plant determines the herbicides you can use.”

“Using residual herbicides, identifying weeds and understanding the difference in solubility and where a product fits best based on soil and moisture are critical to a systems approach to weed management,” Dotray added.

In response to a question about new dicamba labels, Hixson said BASF would not veer from the requirements established by the federal label in Texas, Oklahoma, and New Mexico

Dotray noted that the new registrations come with some significant changes, including bigger buffers, volatility reduction adjuvant requirements and application timing.

“Also, last year some states used 24-C exemptions to alter some regulations. So far this year, states that have applied for a 24-C have been denied.”

Hixson announced that BASF does have one “shiny object” in the pipeline, a new seed trait with tolerance to four herbicides –GLIXTP, pending regulatory approval. He anticipates introduction in 2023, with potentially more availability in 2024.

In the meantime, he said, “Old chemistry still has value.”

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The humble beetle that could rescue a town Share using EmailShare on TwitterShare on FacebookShare on Linkedin(Image credit: Alamy)

Salvinia has an enormously rapid growth rate and can engulf a lake, smothering the ecosystem and killing fish and mammals (Credit: Alamy)

By Nalova Akua29th March 2021An invasive water weed has decimated the wildlife and economy of one of Cameroon’s most significant lakes. But a tiny, ravenous weevil could reverse the region’s fortunes.A

A flock of water birds scavenges for insects on the dense, leafy weed that covers much of Lake Ossa, one of Cameroon’s largest lakes. The water weed is so closely packed that it looks like wide, flat green pasture, and the sure-footed birds pick their way freely across it as if they were walking on land.

Five years ago, Lake Ossa was teeming with freshwater turtles, crocodiles and more than 18 families of fish. It was also a bastion of the African manatee, a species listed as vulnerable on the International Union for Conservation of Nature’s Red List. But today, the lake is eerily quiet and almost empty.

The thick layer of vegetation is Salvinia molesta, a species known locally as kariba weed or simply Salvinia, and it is the cause of this dearth of life in the lake. The invasion has been declared a “conservation emergency” by the IUCN.

Salvinia, a free-floating, green-brown freshwater fern, has already invaded more than 40% of the lake’s 4,000-hectare (15.4-sq-mile) surface, according to the African Marine Mammal Conservation Organisation (AMMCO), a Cameroonian non-governmental environmental organisation.

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Not far from the lake’s shore, an army of weevils is now being mass-reared as a defence against Salvinia

Decimating the lake’s wildlife, and compromising the main source of income for the local population, the Salvinia takeover has been rapid and seemingly unstoppable. Lake Ossa is only one in a long line of freshwater bodies to be engulfed by Salvinia. As this invasive weed has spread around the world, from Brazil and Argentina to Australia, the efforts to control it have struggled to keep pace with the plant’s prolific growth.

But there is hope for Lake Ossa, and it comes in the shape of a small, innocuous-looking but remarkably powerful water-dwelling beetle. Not far from the lake’s shore, an army of weevils is now being mass-reared as a defence against Salvinia.Lake Ossa is one of the largest lakes in Cameroon, and was home to a wealth of biodiversity before Salvinia arrived (Credit: AMMCO)

Lake Ossa is one of the largest lakes in Cameroon, and was home to a wealth of biodiversity before Salvinia arrived (Credit: AMMCO)

Lake Ossa is today littered with weed-laden fishing nets – abandoned by the local fisherfolk out of frustration. Wooden fishing boats have been hauled onto the lake’s shorelines – some have been there so long they are starting to rot. Those local fishermen who are still actively fishing in the lake, and the women who sell the fish caught, say they have lost about 80% of their income.

Lake Ossa used to be home to scores of African manatees, one of the most sparsely studied manatee species. Their population in the lake now appears to be declining

In the sweltering late morning heat, I meet Dina Marie-Louise, a fish retailer and resident of the lakeside town of Dizangue, as she disembarks from a wooden fishing boat. In the local business for 22 years, Dina has been visiting fishermen in the lake to buy their catch. Today, she frowns at the few fish in her basket. “Salvinia is killing us,” she says. “Seven of my 12 children have dropped out of school because of financial difficulties caused by Salvinia.”

Roland Ngolle, who has been fishing in the lake for 12 years, paints a similar picture. “We are running out of space to fish in this lake. If nothing is done, Salvinia will engulf all of Lake Ossa,” Ngolle says. “More than 100 fishermen used to visit this lake in a single morning. Today less than five come to fish. Everybody is discouraged.”

As well as fish, Lake Ossa used to be home to scores of African manatees, one of the most sparsely studied manatee species. Their population in the lake now appears to be declining. Many of the manatees are thought to be leaving the lake for its surrounding rivers, where they have better access to food, says Aristide Takoukam Kamla, founder of AMMCO.The larvae of the Salvinia weevil are highly destructive and can bring a freshwater habtitat back into ecological balance (Credit: Alamy)

The larvae of the Salvinia weevil are highly destructive and can bring a freshwater habtitat back into ecological balance (Credit: Alamy)

Salvinia is native to southern Brazil and northern Argentina, but it can spread between water bodies by wind, water currents, floods, animals and people. “[The] human factor is partly to blame for the presence of the invasive plant in the Cameroon lake,” says Kamla.

As well as physically moving the plant from one place to another, for example when it hitches a ride on boats, human activity is also thought to be responsible for allowing Salvinia to thrive in the lake.

“We noticed a heavy concentration of nutrients such as nitrogen and phosphorous in Lake Ossa in 2016 – doubling from the historical value of 1985,” says Kamla. “This was a signal that something was happening in the lake called eutrophication, which is simply the enrichment of the lake in terms of nutrients.”

That made conditions perfect for Salvinia to proliferate. “The carpet formed by the plant at the surface prevents light from penetrating the water column and therefore reduces photosynthesis of phytoplankton on which most fish species feed,” says Kamla. “This results in a drastic depletion of fish production.”

With a fast-growing plant that can double in size every 10 days, the plant’s growth is almost unstoppable. “The absence of [Salvinia’s] natural enemies in a foreign environment facilitates its fast growth rate,” says Lum Fontem, an independent plant scientist based in Cameroon.Numbers of the African manatee, pictured here in captivity, are in decline (Credit: Getty Images)

Numbers of the African manatee, pictured here in captivity, are in decline (Credit: Getty Images)

At every strategic corner of the bumpy earth roads around Dizangue, billboards carry messages alerting villagers and visitors to the Salvinia problem. Messages such as “Youths, Let’s Save Lake Ossa”; “Let’s Save Our Lake From Salvinia Invasion” appear on countless signs around the town. This may be Cameroon’s first experience of a Salvinia invasion, but there has already been an intensive response to it.

There are three main ways that the weed can be removed. The first, and most physically demanding, is removing it manually. “This includes hand-pulling, mostly for low infestation, and the use of specialised equipment, for high infestation,” says Fontem. “This method is labour-intensive, tedious and time-consuming.”

Since 2019, AMMCO has been mobilising locals to remove the plant manually to reduce the scope of spread. But it has not been without challenges. “This method is very demanding given that the invasive plant multiplies very quickly,” says Kamla. “We removed over 200 tonnes of Salvinia from the lake in 2019 and 2020. Yet, no impact was felt.”

This is because manual removal of Salvinia alone is not enough to control the weed, Lum says. Any plant left in the water will rapidly grow to replenish what has been stripped away.

The second option is chemical control, which involves the application of herbicides to kill the weed. But this comes with its own ecological drawbacks, as the herbicides pose a risk to other plants and could harm the lake’s other organisms. So far, the chemical approach has not been tried at Lake Ossa, and scientists including Fontem caution against trying it.

But there is one final option that could relieve Lake Ossa of Salvinia and restore its ecosystem: a small, brown-black water beetle native to Brazil known as the Salvinia weevil, which feeds almost exclusively on the weed. Measuring just 2-3.5mm long in its adult form, this tiny insect is equipped with a long, sturdy snout. But it is the weevil larvae that are devastating to the Salvinia by burrowing into the plant’s rootstalks and causing fatal damage.Removing Salivinia by hand is very labour intensive, but so far it is the only method that has been attempted at Lake Ossa (Credit: AMMCO)

Removing Salivinia by hand is very labour intensive, but so far it is the only method that has been attempted at Lake Ossa (Credit: AMMCO)

The Salvinia weevil was discovered by Wendy Forno, a scientist at Australia’s government research agency CSIRO, while carrying out surveys in South America between 1978 and 1982. The first releases of the weevil as a biological agent to destroy Salvinia were at Lake Moondarra, Mount Isa, Australia in 1980, with remarkable success.   

“Lake Moondarra is mostly clear of Salvinia today. Fifty thousand tonnes of Salvinia on the lake was killed by weevils over a 400-hectare (1.5-sq-mile) infestation,” says Matthew Purcell, director of the Australian Biological Control Laboratory, a facility run by the United States Department of Agriculture and CSIRO.

“The weevil – both adults and larvae – only feeds on this fern and not on other aquatic plants,” says Purcell. “As the plants increase seasonally, so do the weevils. The weevils [and] Salvinia constantly increase and decrease through the seasons in balance.” The weevils never fully eradicate the weed, but help to “return the system to a balance”, says Purcell.  

The weevil was also deployed in the Senegal River in the early 2000s, where it had similar success, says Arnold Pieterse, formerly a senior staff member of the Netherlands’ Royal Tropical Institute, now retired. He, too, underlines that the weevils’ strong preference for Salvinia as a food crop makes it an appealing choice for Salvinia control. “It has irrefutably been proven that the insects do not form any danger to the environment or crops,” says Pieterse.

South Africa, too, has successfully brought Salvinia molesta under control thanks to the release of the weevil into its fresh water systems since 1985. “South Africa had a number of systems infested with the weed throughout the country, mainly smaller impoundments and rivers,” says Julie Coetzee, deputy director and manager of the Aquatic Weed Biocontrol Programme at Rhodes University, South Africa. These waters took between one to three years to clear, depending on the nutrients in the water, and the climate. “We still do have some infestations appearing,” Coetzee says, but “once weevils have been released, we typically get clearing with a season”.The Salvinia weevil was first tried as a method to control the weed in Australia, where it has also invaded rivers and lakes (Credit: Getty Images)

The Salvinia weevil was first tried as a method to control the weed in Australia, where it has also invaded rivers and lakes (Credit: Getty Images)

Though the Salvinia has no defence against the weevil, the weevils themselves have weaknesses. “No drawbacks were experienced initially but nowadays, we have noticed that there are sites where infestations have persisted, particularly in shaded sites,” says Coetzee. “We have also discovered a parasitic alga infecting [the weevil] population.” This alga, called Helicosporidium, reduces the weevil’s ability to reproduce.

Nevertheless, Coetzee is optimistic that weevils could clear Cameroon’s Lake Ossa of Salvinia. “Implementing a biological control programme in Cameroon is the most ecologically friendly, economically sustainable option for control of Salvinia,” she says. “Given the size of the infestation on the lake, it is going to take a while for the control agent populations to build up to sizes that will damage the plants, and cause them to sink. This is not a fast process. Patience is key.”

Purcell, too, is hopeful that the weevils could rejuvenate Lake Ossa. “The weevils should work in Cameroon. Most control is achieved within three years,” he says. “The control lasts indefinitely, much better than spraying which must be reapplied every year and every season, with negative consequences to the aquatic environment.”

It may not be much longer before Lake Ossa becomes the next Salvinia-ridden water body to welcome weevils. A task force involving several of Cameroon’s government ministries has been set up to oversee the eradication of Salvinia in the lake through the release of the weevils.

The local people of Lake Ossa, though, are frustrated at the pace of action. “Fishing is our only source of income. We are running out of patience,” says Jean Pierre Nga, a fisherman. Dora Sih, a fish seller in the business for 25 years, agrees: “Things are not moving.”

But in AMMCO and their partners’ facilities in Dizangue, the stock of weevils is steadily growing. “They will be released into the lake as soon as we receive the authorisation permit from the government,” Kamla says. “And we hope that after two or three years, we will overcome this invasive plant.”

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