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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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What have we learned about kochia management?

TAGS: MANAGEMENTPhoto courtesy of Nevin LawrenceKochia in a continuous corn field after four years of ALS-inhibiting herbicideKOCHIA CONTROL: Kochia is a tough weed to beat, and it can cause real trouble in crops if it is not controlled. In this photo, you can see the kochia pressure in a continuous corn field after four years of using an ALS-inhibiting herbicide.Extension Crop Connection: Kochia remains a tough weed, but integrated weed management can help win the battle.

Nevin Lawrence | Apr 12, 2021

Kochia remains one of the most challenging weeds to control in western Nebraska. Kochia can be resistant to Group 5 (atrazine), Group 2 (imazamox), Group 9 (glyphosate) and Group 4 (dicamba) herbicides in western Nebraska.

While there are still many herbicides available to irrigated corn growers, those who grow dry beans and sugarbeets have few options because of crop rotation restrictions. When a grower runs out of herbicide options, what can they do?

IWM to the rescue

Integrated weed management is often discussed as the solution. A simple definition of IWM is the strategic use of all the tools a farmer has available, including herbicides, tillage, crop selection, crop rotation, cover crops and other cultural practices.

Does IWM actually work? In 2014, a study was established in Scottsbluff, Neb., to find out. The study ran for four years, concluding in 2017. The goal of this study was to use IWM to target kochia in an irrigated crop rotation.

Each site was established by seeding a mix of kochia biotypes of which 95% were susceptible to Group 2 (ALS-inhibiting herbicides) and 5% were resistant to Group 2 herbicides. The seed mixture used created a “low level” of resistance in the seed bank, which simulates the early stages of herbicide-resistance development.

3 strategies

There were three IWM strategies, including the use of tillage, crop rotation and herbicide strategy. The tillage strategy used two different treatments — minimal tillage or intensive tillage.

Four crop rotations were established — four years of continuous corn; a corn-sugarbeet-corn-sugarbeet rotation; a corn-sugarbeet-corn-dry bean rotation; and finally, a small grain-sugarbeet-corn-dry bean rotation.

The final strategy was herbicide use, with three different treatments. This included a Group 2 herbicide-only treatment, where only herbicides that wouldn’t control the resistant kochia were applied every single year.

Table shows Kochia density per square yard on various crops after 4 yearsAnother was a herbicide mode-of-action rotation, where a Group 2-alternative herbicide rotation and herbicide effective for Group 2-resistant kochia were used every other year. In corn for example, the effective herbicide was a tank mixture of glyphosate and dicamba.

The last treatment was mixing MOAs, where an effective herbicide treatment was mixed with a Group 2 herbicide each year. For the rotation herbicide treatment, in 2014 and 2016, the alternative herbicide was used, and in 2015 and 2017, the Group 2 herbicide was used.

Results are in

After four years, kochia density ranged from as low as 0 to 40 kochia plants per square yard, with seed production as high as 8,000 seeds per square yard. Yield reduction was significant — sugarbeet and dry bean plots experienced total yield loss, and corn yield was reduced from 200 to 60 bushels per acre from the highest kochia densities. Wheat, however, was not greatly affected by kochia competition, always yielding between 55 to 60 bushels.

So, what worked in reducing kochia numbers over four years? The obvious winner was using herbicide mixtures, with low kochia density observed regardless of tillage system or crop rotation.

But what if good herbicides are not available? Including wheat in the rotation helped tremendously, even when an ALS herbicide was used every year. In the sugarbeet-corn and sugarbeet-corn-dry bean rotation, kochia density was reduced from near 40 plants every square yard down to only seven, even when using an herbicide that didn’t work.

Wheat, in irrigated systems, is great at reducing kochia emergence early in the season. Although this study didn’t consider wheat as a cover crop, a similar benefit may be observed by using any small grain — wheat, barley, oats, rye or triticale — as a cover crop preceding other crops. Small grains close rows quickly and smother early plants before they have a chance to emerge in the spring.

Lawrence is a Nebraska Extension weed management specialist.

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The following link will take you to a recording of the parthenium webinar presented by the FTF Innovation Lab at VA Tech presented March 30, 2021.

https://drive.google.com/drive/folders/1BOSAFBic_HZo1k7qRa2MkqbDoXUQxDpm?usp=sharing

Housekeeping information/instructions                 Sara Hendery                     5 minutes           

Introduction to the webinar:                                   R. Muniappan                 10 minutes

Biological control of parthenium in Australia:       K. Dhileepan                      15 minutes

Biological control of parthenium in South Africa: Lorraine Strathie               10 minutes

Biological control of parthenium in East Africa:   Wondi Mersie                    10 minutes

Biological control of Parthenium in India:            N. Bakthavatsalam              5 minutes

Biological control of parthenium in Nepal:          P.K. Jha                               5 minutes

Biological control of parthenium in Pakistan       Kazam Ali                            5 minutes

Discussion/questions and answers                                                                  50 minutes

Closing remarks                                                  Van Crowder                   5 minutes

For further information contact:

Sara Hendery

Communications Coordinator

IPM Innovation Lab

saraeh91@vt.edu

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Damage from invasive species ‘trebling every decade’

Mosquitoes, rats and termites among species that have hitched ride on trade routes, causing at least $1.3tn of damage

Fall armyworm
The fall armyworm arrived in Africa in 2016 and has now invaded dozens of countries. Photograph: Grant Heilman Photography/Alamy

Damian Carrington Environment editor@dpcarringtonWed 31 Mar 2021 11.00 EDT

The costs of damage caused by invasions of alien species across the world is trebling every decade, research has found.

Mosquitoes, rats, ragweeds and termites are among the species that have hitched a ride on globalised trade routes, bringing disease, crop destruction and damage to buildings. The scientists calculated the costs at $1.3tn (£944bn) since 1970, and said even this “staggering sum” was likely to be a big underestimate as much damage is unreported.

The rapidly growing costs show no sign of slowing down, the researchers said, and are more than 10 times higher than the funding for preventing or dealing with these biological invasions. They said global action to combat invasive species remained limited, mostly because the “profound” impacts are poorly understood by the public and politicians.

Mosquitoes from the Aedes genus, such as the tiger mosquito, spread Zika, dengue, yellow fever and other viruses, and were responsible for the biggest recorded costs. Invasive rodents such as the black rat, grey squirrel, coypu and house mouse also cause severe damage to human health, crops and food stores and to native wildlife.

Formosan termites, voracious consumers of wood, are a particular problem in the US, while the red fire ant has spread from its South American home to Australia, New Zealand, several Asian and Caribbean countries and the US. The fall armyworm, which can destroy many crops, arrived in Africa in 2016 and has now invaded dozens of countries.

“The economic costs of invasive alien species since 1970 are tremendous, steadily increasing, but still massively underestimated,” said Christophe Diagne, at the Université Paris-Saclay, France, and who led the research. He said the rising damage mirrored the growth of international trade and the expanding area of farmland and settlements that the invaders can damage.Advertisement

Prof Corey Bradshaw, of Flinders University in Australia, who was part of the study team, said: “The quicker you detect invasive species and the quicker you act, the cheaper it is in the long run. So really good detection at ports and airports and then rapid responses are going to cost you orders of magnitude less money than the damage.”

He said consumers ended up paying for the damage via increased prices for food and other products, and higher healthcare costs.

The research, published in the journal Nature, analysed more than 1,300 estimates of damage by invasive animals and plants. Costs were highest in the US, India, China and Brazil, but this probably reflects where the problems have been most reported. There is little or no data in many other parts of the world.

Some earlier cost estimates indicated much higher damages – as much as $1.4tn a year – but Bradshaw said these were largely based on poor or speculative assessments. “Some were not even ‘back of the envelope’ – there was no envelope,” he said.

The new analysis was deliberately conservative, using only estimates based on observed data. “But there are so many unquantifiables from a monetary perspective, like ecosystem damage and lost productivity, so it’s still the tip of the iceberg,” said Bradshaw. The true costs could be 10 times higher, he said.

Biological invasions are known to be increasing and so the rising cost estimates are unlikely to be solely the result of increased reporting of damage. Either way, the scientists said, “they robustly show staggering amounts” and “a huge economic burden”.

Prof Helen Roy, of the UK Centre for Ecology & Hydrology, who was not part of the research team, said: “The most important aspect of this research is showing the rising costs, regardless of the exact figure. Overall it is a very useful paper and has some excellent recommendations. It also gives some cause for optimism – there are ways to prevent arrival or manage invasive alien species that become established.”

Bradshaw said cinnamon fungus, which rots the roots of plants including grape vines, was one of Australia’s most damaging invasive species. “I have a little farm and it’s killed all of my chestnuts. So we’re slowly replacing those with trees that are resistant”.

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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.

Story continues below

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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John Deere using machine learning to reduce herbicide use

Melody Labinsky

Melody Labinsky@MelodyLabinsky4 Mar 2021, 4:30 p.m.On Farm

John Deere Australia and New Zealand managing director Luke Chandler spoke at the Rural Press Club of Queensland last week.

 John Deere Australia and New Zealand managing director Luke Chandler spoke at the Rural Press Club of Queensland last week.Aa

Machine learning technology is set to reduce herbicide use by up to 80 per cent, according to John Deere’s Australia and New Zealand managing director Luke Chandler.

Mr Chandler said this would be achieved by moving from a whole-of-field approach to a plant-by-plant management strategy.

He said global agriculture was at an inflection point and technological developments would help drive productivity.

Farmers across the world have been chasing economies of scale and the company’s focus had been on building bigger, faster and stronger machinery to meet that growth, he said.

“That’s still important but as we shift towards this next frontier of agriculture, we really see machinery being driven by automation, easier to use, more precise types of technologies.”

In 2017, John Deere acquired Silicon Valley company Blue River Technology for US$305 million.

By using Blue River’s deep learning algorithms and artificial intelligence programming and embedding it on the “hard iron of John Deere machines”, the company hopes to take agriculture’s productivity to the next level.

Mr Chandler spoke about the company’s focus on innovation and how it can help farmers grow the food and fibre sector at the Rural Press Club of Queensland last week.

“While you might hear a lot about ag tech being a new industry, it’s not new for us and it’s not new for us in Australia,” he said.

Mr Chandler pointed to the role of cotton and grains farmers in northern NSW in helping to develop GPS and yield mapping technology, which has become a major part of precision agriculture, and is used around the world.

John Deere has grown from its humble beginnings in Illinois 184 years ago, into one of the world’s largest agricultural machinery manufacturers.

Together with dealerships, the company employs 4500 people across Australia and New Zealand.

John Deere is also looking to bring its total number of tech apprentices to 1200, predominately in rural and regional communities.
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Controlling herbicide resistance takes persuading

TAGS: WEEDSRESISTANCE MANAGEMENTBrad Hairebrad-haire-farm-press-pigweed-smallish-cotton-GA.jpgCharlie Cahoon urges farmers to be on the lookout for Palmer amaranth surviving 2,4-D or dicamba. Integrated pest management is key for tackling herbicide resistance.

John Hart | Jan 04, 2021

The answers to managing herbicide resistance are fairly simple, the hard part comes in persuading farmers to implement the practices that do the most good.

Charlie Cahoon, North Carolina State University Extension weed specialist, says integrated pest management is key. Farmers need to rotate herbicide chemistries and turn to cultural and mechanical methods to alleviate some of the pressure on over-used herbicides.

“As Extension specialists, we’ve been using fire and brimstone. We think one of the tactics that drives folks to change practices on their farm is to scare them to death,” Cahoon said in a presentation at the virtual North Carolina Crop Protection School Dec. 2.

“My daddy has trained bird dogs his whole life. He used to think the way to train a dog was to use discipline. My three-year old daughter just taught him it is quite easy to train a dog with a handful of treats. There are studies to back this up, rewarding good behavior. I think that’s what we are having to learn right now with pesticide resistance: How do we get our growers to put into practice the tactics we’ve been preaching for years,” Cahoon said.

One option, Cahoon says, is providing farmers an economic incentive to implement integrated pest management practices. But where will the incentive come from?

Companies do have inventive programs, but Cahoon believes the incentive programs must cross company lines to encourage farmers to rotate modes of action and implement cultural practices to better control weeds.

Moreover, incentives must be in place for farmers to use cover crops, better crop rotation and other tools such as harvest weed seed control. “It really needs to be a whole industry initiative where we all get on the same page and say, ‘hey let’s reward some of these good behaviors and try to get ahead of this pesticide resistance issue,” Cahoon said.

Herbicide resistance is a problem that’s not going away.

In North Carolina, Cahoon says there is widespread Palmer amaranth resistance to glyphosate and ALS inhibitors, plus expected resistance to PPO inhibitors. There is common ragweed resistance to glyphosate and ALS inhibitors, primarily in the eastern part of the state. And there is widespread Italian ryegrass resistance to ALS inhibitors, mostly in the southern Piedmont.

Looking to the future, Cahoon said he won’t be surprised if North Carolina farmers begin to see resistance to group 15 herbicides, such a Dual, Warrant, Harness and Zidua.

“We use them repeatedly in most of our crops —  corn, soybeans, cotton, peanuts, and sweet potatoes. We are putting quite a bit of pressure on the group 15s, and there is already group 15 Palmer amaranth resistance in Arkansas and also a cousin to Palmer amaranth, waterhemp, is resistant to the group 15s in Illinois,” Cahoon said.

And as the use of dicamba and 2,4-D continues to grow, resistance to these chemistries can be expected as well. “There is evidence we are abusing dicamba and 2,4-D like we did glyphosate. That is unacceptable,” Cahoon said.RELATED Pigweed continues to outflank herbicidesNovember 11, 2020More resistant weeds popping up in North CarolinaMarch 5, 2020Building respect and value for soybeansNovember 24, 2020

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Robotic weed removal eliminates need for expensive hand crews

TAGS: TECHNOLOGYTodd FitchetteFarmWise weederSingle-

Single-line organic cauliflower is weeded with a robot developed and operated by the Salinas-based FarmWise.FarmWise offers a business model that provides weeding services, freeing the grower from having to own and maintain a machine.

Todd Fitchette | Dec 04, 2020

Produce growers in Arizona and California are being introduced to the futuristic world of George Jetson as robots and artificial intelligence replace labor crews used to rogue weeds from lettuce, cauliflower, and other vegetable crops.

Salinas, Calif.-based FarmWise is a service company with a robotic weeding machine capable of rouging weeds at speeds of one-to-two miles per hour. This eliminates the need for expensive hand crews or chemical herbicides.

The FarmWise weeding machine is part of a service FarmWise provides. Unlike some companies that sell the machines, FarmWise offers a business model that provides weeding services, freeing the grower from having to own and maintain a machine.

The Titan FT35 is the third generation of machines developed by FarmWise. Company Chief Executive Officer Sebastien Boyer said testing on previous generations of machine took place over the past several years. The newest generation of machine is being used commercially in California and Arizona. https://c8c1c3523498a4e6800111cf107f6155.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

The machine uses artificial intelligence to learn the various crops by studying the plant structure, according to Sal Espinoza, regional manager with FarmWise. Once the computer successfully learns the stem structure of the produce plant, the ability to cull weeds is simple. This process can take a few months of machine learning to get it right, Boyer said.

The machines can be outfitted with as many as six weeders. These are the rows of internal components that contain the metal knives that cut through the soil and rogue weeds as cameras track the vegetation and the AI of the onboard computer determines whether the plants are the planted produce, or weeds.

Boyer said his long-term goal is to find additional ways to mechanize the manual labor and tedious tasks performed by human hands. Through the machine learning the AI can distinguish cauliflower, celery, broccoli, and cabbage. Other crops including tomatoes and pepper are being perfected.

The company’s current business model is focused on providing services to produce growers in the desert region of southern California and Arizona after an inaugural run in the Salinas Valley. Boyer said he is also looking at European markets to expand his machine weeding technology.

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Sustainable Pulse

US EPA Evaluation Finds Glyphosate Likely to Injure or Kill 93% of Endangered Species

Posted on Nov 28 2020 – 3:21pm by Sustainable Pulse« PREVIOUS| Categorized as

The Environmental Protection Agency released a draft biological evaluation on Wednesday finding that glyphosate is likely to injure or kill 93% of the plants and animals protected under the Endangered Species Act.

Endangered Species

The long-anticipated draft biological evaluation released by the agency’s pesticide office found that 1,676 endangered species are likely to be harmed by glyphosate, the active ingredient in Roundup and the world’s most-used pesticide.

The draft biological opinion also found that glyphosate adversely modifies critical habitat for 759 endangered species, or 96% of all species for which critical habitat has been designated.

“The hideous impacts of glyphosate on the nation’s most endangered species are impossible to ignore now,” said Lori Ann Burd, environmental health director at the Center for Biological Diversity. “Glyphosate use is so widespread that even the EPA’s notoriously industry-friendly pesticide office had to conclude that there are hardly any endangered species that can manage to evade its toxic impacts.”

Glyphosate Box

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Hundreds of millions of pounds of glyphosate are used each year in the United States, mostly in agriculture but also on lawns, gardens, landscaping, roadsides, schoolyards, national forests, rangelands, power lines and more.

According to the EPA, 280 million pounds of glyphosate are used just in agriculture, and glyphosate is sprayed on 298 million acres of crop land each year. Eighty-four percent of glyphosate pounds applied in agriculture are applied to soy, corn and cotton, commodity crops that are genetically engineered to tolerate being drenched with quantities of glyphosate that would normally kill a plant.

Glyphosate is also widely used in oats, wheat, pulses, fruit and vegetable production.

“If we want to stop the extinction of amazing creatures like monarch butterflies, we need the EPA to take action to stop the out-of-control spraying of deadly poisons,” Burd continued.

The EPA has, for decades, steadfastly refused to comply with its obligation under the Endangered Species Act to assess the harms of pesticides to protected plants and animals. But it was finally forced to do this evaluation under the terms of a 2016 legal agreement with the Center for Biological Diversity.

Emails obtained in litigation brought against Monsanto/Bayer by cancer victims and their families have uncovered a disturbingly cozy relationship between the agency and the company on matters involving the glyphosate risk assessment.

In one example, when the U.S. Department of Health and Human Services announced it would be reviewing glyphosate’s safety, an EPA official assured Monsanto he would work to thwart the review, saying, “If I can kill this, I should get a medal.” The Health and Human Services review was delayed for three years.on.”

Earlier this year, relying on confidential industry research, the EPA reapproved glyphosate. The EPA’s assessment contradicts a 2015 World Health Organization analysis of published research that determined glyphosate is a probable carcinogen.

Sustainable Pulse

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Thursday, April 5, 2018

AfricaRice launches free mobile app for rice weed control in Africa

The Africa Rice Center (AfricaRice) has launched a powerful new decision-support tool, called ‘RiceAdvice-WeedManager,’ to help African rice farmers find the most effective and cost-efficient weed management strategies, matching their specific farming conditions and available resources.

Potentially all rice farmers in sub-Saharan Africa (SSA) can benefit from this interactive tool as it can be used across rice-growing environments, from rainfed uplands to fully irrigated lowlands, leading to significant improvements in efficiency, productivity and incomes.

RiceAdvice-WeedManager

Weeds are serious constraints to rice production in SSA across all rice environments. AfricaRice surveys indicate that farmers perceive weed infestation as the predominant biotic constraint to rice production in SSA. Annual weed-inflicted yield losses in rice are conservatively estimated at 2.2 million tons per year in SSA, resulting in at least US$ 1.5 billon losses per year.

It is estimated that improved weed control, when combined with good soil fertility management, can raise rice yields by 1 ton per ha. Improved weed management is therefore vital to prevent losses in rice yield and production costs. For this, rice farmers in SSA need timely and reliable advice to make better decisions on the most appropriate weed control options. But at present they have limited access to such information.

The WeedManager app has been developed in close association with Co-Capacity, The Netherlands, with support from the CGIAR Research Program on Rice Agri-food Systems (RICE). It is strongly based on research findings of AfricaRice and its partners, who have long been involved in developing efficient weed management strategies that are affordable and feasible for resource-poor rice farmers in SSA.

The app is now being field-tested with farmers in Nigeria and Tanzania with the help of the Competitive African Rice Initiative (CARI), commissioned by the German Federal Ministry for Economic Cooperation and Development (BMZ). “We are planning to organize training in the use of WeedManager app, which is an exciting tool for weed management,” said Dr Kazuki Saito, AfricaRice Agronomist.

The app provides a range of adapted recommendations for weed management – before, during and after the main rice-cropping season – based on information entered for each participating farmer relating to his/her field conditions, available resources (financial, human and natural resources and equipment) and prevailing weed problems. Each farmer decides which of the recommendations to adopt and can then be further advised and monitored by service providers.

“The WeedManager app stimulates adoption of targeted and integrated weed management practices by smallholder rice farmers in SSA, helping to reduce their reliance on manual weeding. This contributes to sustainable productivity enhancement leading to food security and income generation,” explains Dr Jonne Rodenburg, former AfricaRice agronomist, who has spearheaded the development of the WeedManager app. Dr Rodenburg is currently Senior Lecturer/Researcher Agroecology at the Natural Resources Institute (NRI) of the University of Greenwich, United Kingdom.

The WeedManager app can be used by farmers, extension workers, private companies involved in rice agri-business, development agencies and other stakeholders in Africa, who are interested in getting expert advice on weed management for rice production. It can also open opportunities for young professionals to serve as service providers by delivering personalized recommendations generated by the app to smallholder rice farmers and by assisting farmers during the implementation of the recommendations.

The WeedManager app can be freely downloaded from the Google Play Store on any Android device (smartphone or tablet). It is available in English and French, and other language versions are planned. The WeedManager app uses the same login data as the RiceAdvice app earlier launched by AfricaRice.

Related links :

Posted by AfricaRice AfricaRice at 6:35 AM

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