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Researchers determine groundbreaking new way to identify pesticide resistance: ‘I’m really excited about this study’
Tina Deines
Sun, April 7, 2024 at 12:00 PM CDT·2 min read
Researchers are exploring an exciting new approach that uses genomics to help monitor and identify pesticide resistance in the insects that munch on our crops.
Pest management is important for farmers, but insects often become immune to pesticides, making them less effective. In the new research, published in the Proceedings of the National Academy of Science, a team of scientists from the University of Maryland (UMD) presents a new strategy that analyzes genomic changes in pests to monitor and identify emerging resistance to specific toxins early on.
They zoned in on one pest in particular: the corn earworm, a crop-destroying caterpillar that has developed widespread resistance to a number of natural toxins bred into corn. They were able to identify resistance to toxins among these caterpillars after just a single generation of exposure. They also identified how common strategies for avoiding resistance could actually be doing the opposite.
“As it currently stands, the evolution of resistance across many pests of agricultural and public health importance is outpacing the rate at which we can discover new technologies to manage them,” said senior author Megan Fritz, an associate professor of entomology at UMD, per Phys.org. “I’m really excited about this study, because we’re developing the framework for use of genomic approaches to monitor and manage resistance in any system.”
The new research is one of many that is helping farmers to produce more successful harvests.
For instance, a team of American and Chinese researchers found a way to genetically engineer plants that can survive heat waves. University of Minnesota scientists are on their way to developing a “Super Grape” that could stave off powdery mildew and reduce the need for fungicide.
These developments in agriculture come at a critically important time — as our planet continues to warm, there are frequent heat waves and droughts, which threaten our food security. Plus, climate change scientists predict that a warming world will drive a surge in certain insect pests that attack our crops, further threatening food security and causing economic losses for those in the agricultural sector.
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‘Dinosaur’ pesticide law clings to life as SA dithers on poisons reform
Some critics suggest that South Africa remains locked in a chemical culture time warp, where pesticides continue to be cast in a ‘heroic’ role, discouraging less toxic products and non- chemical weed and insect control alternatives. (Photo: schmidtlaw.com / Wikipedia)
There are more than 3,000 registered pesticides sprayed across South Africa, several of which are banned or severely restricted in Europe and other countries because of human and environmental safety risks. Despite the government’s promises to reform outdated pesticide policies, public health experts say there has been little movement.
It has been 77 years since the first law to regulate chemical pesticide safety was passed in this country. This was back in the days of King George VI, Jan Smuts and the Union of South Africa.
Since then, South Africa has become the largest consumer of pesticides in Africa, accounting for roughly a third of all farm chemicals used on the continent.
The primary law regulating pesticides dates back to 1947, but there are more than a dozen other laws, with overall administration fragmented between seven different government departments. (Government Gazette and Wikimedia Commons / Library of Congress Prints and Photographs Division)
Here is one example: The current Act still specifies a fine of “£500” for government officials who unlawfully disclose any confidential business affairs of the agricultural industry.
Juxtaposed against this £500 fine (roughly R12,000 at today’s exchange rate), the current version of the Act only permits a maximum penalty of R1,000 for violations of the country’s main pesticide control law.
The Adjustment of Fines Act of 1991 does provide for a retrospective stiffening of fines using a ratio determined by periodic government notices, so the R1,000 fine may now be closer to R80,000.
Nevertheless, the £500 fine crafted to protect industry secrecy and the derisory scale of maximum fines for pesticide law violations, remain on South Africa’s statute book – stark evidence of an outdated legal legacy and powerful influence of vested industry interests in an era where modern agricultural systems seemingly remain addicted to chemical poisons to sustain the growth of food or cash crops.
As evidence continues to pile up about the serious harm to humanity and the environment from the increasing volumes of pesticides sprayed across the world, the government has failed to implement a series of reforms recommended by its own policy document – the “new” Pesticide Management Policy published 14 years ago.
Several pesticides have been shown to increase the risk of cancer and obesity, along with neurological damage to children, kidney and lung disease and other serious health impacts. (Image: Brewer International / Wikipedia)
There has also been a two-decade delay in passing domestic laws to enforce the Rotterdam Convention, an international treaty ratified by South Africa in 2002 to limit the global movement of banned or severely restricted pesticides.
It was only in May 2021 that Forestry, Fisheries and the Environment Minister Barbara Creecy gazetted new Rotterdam domestic regulations, which introduced new penalties of up to R5-million for pesticide manufacturers and distributors who either import or export hazardous chemical and pesticide formulations in contravention of the international treaty obligations.
But in November 2021, Creecy changed her mind and suspended the implementation of the new regulations for 12 months. Following a further series of delays, she has since repealed the original regulations and published a new version that is only due to take effect in mid-June 2024 (barring further delays).
Creecy’s department has rejected claims of any improper influence from the agrochemicals industry in delaying the new Rotterdam domestic regulations and attributed some of the delays to “substantive” objections that included the apparent omission of CAS chemical registry numbers from the published regulations.
Croplife SA, an industry body whose members include agrochemical companies such as BASF, Bayer, Corteva, UPL and Syngenta, says it is also “not of the opinion that Minister Creecy is intentionally delaying the implementation, but rather ensuring that the regulations are free of errors, which is of paramount importance”.
Nevertheless, documents on its website suggest that it is pushing back against international pressure to phase out at least 29 chemical substances linked to greater risks of cancer, genetic damage and other harms to people, animals and the environment.
Members of the Women on Farms Project marched in Worcester on 5 May 2022 demanding an urgent ban on 67 pesticides. (Photo: Ashraf Hendricks)
At a series of workshops last May for farmers, government officials and journalists, senior Croplife leaders said there was a need to “bring the African narrative more firmly into relevant policy discussions” around the European Green Deal – a recent initiative to protect human health and restore damaged ecosystems. This includes plans to reduce use of the most hazardous pesticide types by 50% by 2030.
According to European Health and Food Safety commissioner Stella Kyriakides: “It is time to change course on how we use pesticides in the EU … We need to reduce the use of chemical pesticides to protect our soil, air and food, and ultimately the health of our citizens. For the first time, we will ban the use of pesticides in public gardens and playgrounds, ensuring that we are all far less exposed in our daily lives.”
According to a European Commission “Farm to Fork” policy document, EU scientific advisers have concluded that the current food system in Europe is no longer sustainable.
“This does not mean that pesticides are not needed. There are cases where satisfactory pest control can only be achieved in commercial food production through the use of chemical pesticides. However, chemical pesticides should be used only as a last resort.”
Rather than intensive pesticide use, the European Union promotes pest management systems where toxic chemicals are used only as a last resort. (Image: European Commission 2022)
The commission also cites a World Health Organisation report which estimates that there are about 1 million cases of unintentional pesticide poisonings every year, leading to approximately 20,000 deaths. A more recent review estimated about 385 million cases of unintentional acute pesticide poisonings occur annually worldwide, including around 11,000 fatalities.
Chemically active pesticides were found in up to 30% of European rivers and lakes, and regulators are worried about the increasing impact on the pollination of food crops at a time when up to 10% of bee and butterfly species in Europe are on the verge of extinction, and 33% are in decline.
Croplife SA has made it clear that it will push back against so-called EU “mirror clauses” that would prohibit South African farmers from using certain pesticides if they export products to Europe – even if these pesticides are legally registered in South Africa.
Global pesticide distributors have frequently been accused of double standards, by peddling in African and other developing countries agrochemical products that have been either banned or severely restricted in Europe because of human safety and environmental concerns.
Croplife SA, however, responds that enforcing European policies on local farmers is a “threat to the government’s right to make decisions for its people based on the local conditions and requirements”.
“Products cannot just be ‘dumped’ in South Africa as some activists claim; they must go through a rigorous registration process that considers the local production conditions and environmental impact.”
Croplife insists that the current regulatory framework in South Africa remains “robust” and “very strong” even though the original Act dates back to 1947.
But that is not how several other interest groups view the 1947 pesticides control law.
Precision farming techniques using drones or modifying the flow rate from spray nozzles can significantly reduce pesticide volumes compared to more conventional manual methods. (Photo: iStock)
Prof Leslie London, a senior University of Cape Town (UCT) public health research expert on pesticide hazards, chemical neurotoxicity and farm worker safety, says: “I think what Croplife really mean is that South Africa has a regulatory environment very favourable to industry. It would be laughable to consider it ‘strong’ unless you mean strongly biased to industry.”
He argues that at a time when many developed countries are adopting policies that promote pesticide reduction, South African policy remains largely out of step with international concerns
The primary 1947 law to control pesticides is regulated by the national Agriculture department, via the Registrar for Pesticides. But because this department is also mandated to promote agricultural expansion, Prof London believes this creates a clear conflict of interest concerning independent pesticide regulation.
He also suggests that the national department has done little to promote the Integrated Pest Management philosophy, which encourages farmers to reduce their reliance on chemical pesticides.
These are some of the alternatives proposed to reduce chemically-intensive farming. (Image: European Commission 2022)
In a journal critique published in 2000, Prof London and fellow UCT public health researcher Prof Hanna-Andrea Rother argued that pesticide regulation fines were “grossly inconsistent with the gravity of offences” while inspectorates were hugely understaffed.
Nearly a quarter of a century later, those derisory fines remain unchanged, and Prof London says that though there has been some “tinkering”, the current pesticide regulation model remains more or less unchanged.
He suggests that South Africa is still locked in a “pesticide culture” that sees intensive chemical control of farm pests as the norm, rather than as a last resort.
“This consent is manufactured by many forces, economic and ideological, and can be seen in the nature of pesticide advertising, and discourses surrounding the heroic role pesticides can play in economic development in the new South Africa,” according to the two researchers..
They noted that 100 to 200 cases of pesticide poisoning were reported every year to the Department of Health (mostly farmworkers or rural residents), while other surveys suggested that the true rates were anything between five and 20 times higher.
Several farm workers live in close proximity to crop fields sprayed from the air, potentially exposing them to toxic spray drift via contaminated air and water. (Photo: Professor Leslie London)
To resolve conflicts of interest and the fragmentation of regulation, the two researchers call for a new independent regulatory body to act as guardian of the public interest, separated from the economic motive to promote agricultural production.
Similar proposals for reform have also been made by Advocate Susannah Cowen SC on behalf of the Real Thing natural health products company.
In a legal opinion submitted to the SA Law Reform Commission in 2021, Cowen draws attention to the apparent double standards of South Africa importing hazardous chemicals from countries where these same chemicals are banned.
Cowen (now a judge of the labour court) said: “No amount of tinkering or amendment can render the 1947 Act fit for purpose in a democratic South Africa. It is wholly outdated.”
At the time of the submission, she said there was also no requirement for periodic safety reviews of currently registered pesticides or re-evaluations of old chemicals.
“The State made important reform commitments in the Pesticide Management Policy for South Africa in 2010. However, these commitments have not been realised and very little has been done since 2010 when these commitments were made.” DM
The Department of Agriculture Land Reform and Rural Development responds:
“The (1947) Act may only be amended once its relevance, applicability, suitability and responsiveness is under question, and so far the Act is still potently applicable
“Over the years, the department has phased out or banned many pesticides of concern under the same Act. We will continue to review the pesticides on concern, and where applicable we will phase out or ban them.
“There have been several regulations under the Act which the Minister has made in order to respond to some substantive recommendations which were part of the 2010 Pesticide Management Policy. The regulations relating to agricultural remedy, as published in Government Notice No. R. 3812 of August 2023, are aimed at addressing the recommendations of the 2010 Pesticide Management Policy.
“The latest regulations were published on 25 August 2023, which, among others, are aimed as phasing active ingredients and their pesticides formulations that potentially may cause cancer, genetic mutation and damages to fertility of a human being (including negatively affecting the unborn child); implementation of the Globally Harmonised System of classification and labelling of chemicals; restrictions of sale and use of certain hazardous pesticides, disclosure by agrochemical companies of amounts the of pesticides sold and other measures.
The Department of Forestry, Fisheries and the Environment (DFFE)responds:
A spokesperson said the department “categorically rejects [suggestions] that it has taken 20 years to implement the Rotterdam Convention. DFFE has been facilitating the exchange of information for more than 17 years (as far back as 2006).”
Commenting on the reasons for a recent series of notices to suspend, repeal or amend the convention’s domestic regulations, the department said it was compelled by law to undertake public participation when developing regulations.
“There were submissions on substantive matters that were submitted after the finalisation of the (Rotterdam) PIC Regulations that influenced the department to reconsider and opt for the suspension of the PIC Regulations. The department rejects claims or any perceptions of improper influence and maintains that the Batho Pele principles of consultation, courtesy and responsiveness remained at the centre of the department’s decision to suspend the regulations while the specific amendments were being attended to.”
Croplife South Africa responds:
Croplife confirmed that it made submissions to Creecy’s department to correct certain errors in the registration status of chemicals listed in the Rotterdam regulations.
Responding to criticism about the “double standards” of selling pesticides in Africa when they were banned in Europe or other developed nations, Croplife said: “It is quite normal for some countries to have plant protection solutions authorised for local use when they are not registered in other countries. Local climatic conditions, pest occurrence, crops and regulatory procedures differ from country to country. Therefore, products can be registered in one country and not in another.”
The industry group acknowledged that current laws only provide for a R1,000 fine for contraventions of the 1947 Act, but noted the government could impose much more severe sanctions – such as a banning or cancelling sales of certain chemical products.
There had also been “several” amendments since 1947, while specific product registrations were reviewed every three years.
New regulations published in August 2023 also contained a clause that a pesticide registration holder was obliged to inform the registrar of any new data pertaining to environmental or human toxicology
“Act No 36 and its supporting regulations provide a robust regulatory framework for plant protection solutions in South Africa. As with any government department, the Act No 36 of 1947 regulatory team could be more efficient if central Treasury provided greater funding. In this way, the approval and registration process could bring newer technologies to South African farmers more quickly.
“Government still has the overall right to approve or not approve a product. But our opinion remains that the system for product registrations can be more efficient, bringing newer technologies to farmers quicker, by better utilising the fees already paid to government for product registrations”.
The Pesticide Risk Tool (PRT) provides growers and IPM pros with detailed risk estimates for 15 different potential environmental and human-health impacts. For risks to pollinators—such as the honey bee (Apis mellifera), shown here on an apple blossom—the PRT considers different exposure routes and includes three separate risk indices to quantify pollinator risk: One for pollinators in the area sprayed while a crop is in bloom, another for pollinators in the area sprayed while a crop is not in bloom, and a third for pollinators immediately outside of the area sprayed. A new report in the Journal of Integrated Pest Management explores the Pesticide Risk Tool and its applications. (Photo via Pixabay)
By Eleanor Meys
Eleanor Meys
The adverse effects of pesticide use on humans and the environment have long been a concern for consumers, growers, and scientists—and rightly so. In the past, we have seen the catastrophic effects when nontarget risks of pesticides are not known or properly considered.
A classic example in the United States was the use of the insecticide DDT (dichloro-diphenyl-trichloroethane) in the 1940s to 1970s. The use of DDT was detrimental to the reproduction of bald eagles and other raptor and fish-eating birds, contributing to several population declines in the mid-20th century. Unfortunately, the high toxicity of the replacement insecticides—organophosphates and carbamates—to birds also led to additional avian casualties in many farm fields.
At this point, we cannot realistically eliminate the need for all pesticides in most crops, but we can make better decisions about the chemicals we use. Fortunately, for us (and the environment), tools are continuously being developed to better inform the selection of pesticides, not only for efficacy but also to minimize environmental and human health risks.
One such tool is the Environmental Impact Quotient (EIQ), developed and supported by Cornell University. The EIQ uses information about a pesticide’s chemical properties to assign certain numerical classifications to risk categories. The numerical classifications and the amount of a pesticide applied are used to calculate a hazard value. The EIQ is essentially a hazard quotient, as opposed to a true risk quotient. (Hazard refers to something that can cause potential harm, while risk refers to the likelihood such harm will occur.) This approach allows the user to compare the output value for different chemicals to determine which pesticide has the least risk. However, these values are only meaningful when numbers are compared to each other. Although the EIQ has received criticism in the scientific literature, the method has been widely adopted during the past 30 years.
A group of colleagues and I recently reviewed a lesser-known risk quantification tool, the Pesticide Risk Tool (PRT), developed by the IPM Institute in Madison, Wisconsin. The PRT is an online tool that allows users to assess pesticide risk for 15 different human-health and environmental measurement scales, or indices. Some examples of the PRT categories include impacts to birds, earthworms, aquatic algae, human workers, and pollinators. We introduce and explore the Pesticide Risk Tool in an article published in January in the Journal of Integrated Pest Management.
What makes the PRT unique is that it goes further than the classic hazard quotient to develop a true risk quotient. We consider the PRT a true risk quotient because, for several of its environmental indices, it calculates the probability of a nontarget environmental effect occurring from a given pesticide application. This probability is determined by analysis of relevant field studies. For example, the “avian acute” index calculates the probability (between 0 percent and 100 percent) that a chemical application will cause avian mortality. The risk output from the PRT gives the user an understanding of how a pesticide can affect the environment. Users can still compare chemicals, similar to hazard quotients, but comparisons from the PRT are based on the probability of real-world effects instead of arbitrary numbers.
Beyond characterizing real-world risk, the PRT has many other advantages compared to similar tools. The PRT uses scientifically sound methods in its calculations, including either the use of data from field-derived studies, as mentioned above, or the best risk-assessment processes available to date. The PRT’s online tool presents results in both table and graph formats.
The Pesticide Risk Tool provides a graphical output, such as shown here, to summarize the risk associated with each pesticide for each environmental index. These graphs provide an easy yet informative way to visualize environmental risk. By viewing the graph, one can quickly determine whether a pesticide is considered low, medium, or high-risk, corresponding to the graph’s yellow, orange, and red shading, respectively. (Images originally published in Meys et al 2024, Journal of Integrated Pest Management)
Currently, insects that humans rely on to pollinate our crops are threatened, with one threat being pesticide use. A pesticide’s effect on pollinators is a complicated problem due to multiple pathways of pesticide exposure—for example, via direct contact within a field, from drift near the field edges, or through consumption of contaminated pollen and nectar. The PRT considers these different exposure routes and includes three separate indices to quantify pollinator risk: One for pollinators in the area sprayed while a crop is in bloom, another for pollinators in the area sprayed while a crop is not in bloom, and a third for pollinators immediately outside of the area sprayed. Having these separate indices allows for an improved risk profile and subsequent selection of pesticide use to reduce the risk to pollinators throughout the year.
In summary, we believe the PRT to be a successful evolution of risk assessment tools beyond simple hazard quotients such as the EIQ, and it provides more accurate results with greater real-world meaning. The PRT produces more advanced ways to characterize pesticide risk, aiding in formulating safer pesticide regimens and finding solutions to mitigate environmental and human risk. As one example, the PRT model has been tailored and adopted by the Lodi Wine Growers of California as a key element of their LODI RULES Sustainability Certification program, supporting the value of the PRT in documenting sustainable pest management strategies.
With the advantages of the PRT outlined here, we encourage researchers, IPM practitioners, and growers to evaluate the PRT as a new tool for making better pest management decisions when using pesticides.
Eleanor Meys is a master’s student and graduate research assistant in crop sciences at the University of Illinois, Urbana-Champaign, who completed her bachelor’s degree in fisheries, wildlife, and conservation biology at the University of Minnesota in 2023. Email: emeys2@illinois.edu.
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Use of drone in detecting botrytis. – Photo: Greenport Duin- en Bollenstreek
Six growers from the Dutch Dune and Bulb Region started working with Unmanned Valley in the Remote Sensing for Ornamental Cultivation project. The question is: how can you use satellite and drone technology to detect diseases and pests at an earlier stage?
Early detection allows you to take more targeted action. The main goal: using fewer crop protection agents and a healthy crop. Duch organisation Greenport pays attention to this project wherein botrytis was chosen. In retrospect, a good choice because in the spring of 2023 there was often botrytis in the crop. This allowed the drone to collect a lot of data. The thousands of photos taken by the drone are assessed (annotated) by the growers to see whether botrytis is present. This is the manual work that also belongs to artificial intelligence (AI): feeding the system with information.
Next steps
These images eventually lead to a model. Can this model accurately recognize botrytis? This will be investigated at a later stage. You can link this model to protection: earlier or more targeted. Another step further: predicting where – also – botrytis will occur, by connecting more sensors to it. Also consider soil sensors, local weather conditions.
Targeted protection is already possible: it is possible to control per cap and there are already techniques that do not spray, but touch the plant.
One of the growers Henk Verdegaal has been involved in precision agriculture for some time: the steps being taken are slow but steady: new techniques are becoming available. For example, a drone can already fly independently (legislation still requires a pilot) and AI will ensure that data is converted faster and better into information that can help it make decisions.
Sizes vary, but a sprayer drone can typically apply a 10′ to 40′ swath, depending on the wingspan, with bigger drones covering up to 50 acres an hour.(Bryan Young)
Squinting through the morning sun, Jesse Patrick watches the top of his corn crop whip in the downdraft of a large spray drone pipping fungicides into the canopy.“The drone is only putting out 2 gal. an acre, but the thing that surprised me was the swath and amount of downdraft coming off of it even flying 15′ above the corn,” Patrick recalls.This seventh-generation farmer, who grows soybeans, corn, wheat, hay and sorghum, is used to battling weeds and disease in his heavy Georgia clay soils about an hour east of Atlanta. Treating those yield robbers with a drone, however, is new.
“When the drone lands, you pull the battery out, fill it up, put in a new battery and the whole thing takes about 15 seconds,” Patrick says. “It’s a pretty well-oiled machine.”Drone-driven sprayers are popping up across the country as better batteries, longer flight times and bigger machines make it possible to spray sizable acreage in a timely manner.“There’s a 10-gal. tank so every 5 acres he has to come back to refill,” Patrick explains. “We knocked out 150 acres in about four to six hours.”
Does it Work?
While farmers such as Patrick find the technology useful, especially for spot spraying and targeting fields in less-than-ideal conditions, weed scientists are buzzing with more caution.“We [weed scientists] are very sensitive about the resistance issue we have in weeds to herbicides, and as I’ve heard about using drones for applications, I wonder who’s testing it,” says Bryan Young, a weed scientist at Purdue University. “I wondered if we are going to generate more resistance, if this is a sub-optimal application, and I wasn’t getting a lot of answers.”That kick-started a research project into drone sprayers and verifying the new application method is effective enough to do the job. Young has witnessed the potential benefits of sprayer drones; however, as with all new technology, he’s still quantifying and investigating the results.
“I was looking around for any guidelines on the best spray drone design in terms of nozzles and boom configuration,” Young says. “Frankly, to date, I can’t tell you where the industry is headed for sure or what is the best setup for herbicide application. This is an emerging technology for commercial applications in the U.S.”Drone operators often tout the strong down draft helping push product into the canopy, but then fly at higher elevations to maximize field coverage or spray swath. Young says these application methods are significantly different than traditional aerial applications, and it’s why he’s part of a working group looking into whether product labels should include separate drone application guidelines.“Right now, the U.S. EPA has left it up to each state to determine whether drones can be used for herbicide applications following the aerial component of the herbicide labels,” Young explains. “Not all states agree on that and not all countries agree.”Then there’s the question of drift. It’s still being investigated exactly how much different spraying with a drone is versus a ground-based sprayer or even by airplane.
Wind Tunnel Testing
“Underneath the drone’s propellers what would normally be a flat fan spraying from the nozzle, all of a sudden, [the pattern] starts to bend and oscillate,” explains Kyle Butz, a technical adviser with Spray Analytics.He’s been working with Sidaard Gunasekaran, a professor of mechanical and aerospace engineering at the University of Dayton, to test the effects of drone propellers on pesticide and herbicide application during flight. The two recently released their findings on droplet drift using the university’s low-speed wind tunnel.“I think Kyle and I both asked the same question: On what basis are they deciding where to put the nozzles?” Gunasekaran recounts. “It turns out, they just take an agriculture nozzle, stick it underneath the propeller and then go fly without understanding the aerodynamics or the right location for that nozzle.”In search of answers, Gunasekaran and Butz developed a test rig with two propellers, a spray nozzle and a measurement system. They confirmed the propellers do in fact pull droplets back into the down draft while blowing smaller droplets out away from the target zone.“If you have smaller droplets, called fines, which are anything under 140 microns, they are prone to drift,” Gunasekaran says.From a sprayer’s perspective, however, there’s always been a balancing act between droplet sizes and efficacy.“Ultimately, spray applications come down to, one, droplets have to be large enough to safely reach the target, and two, they have to be small enough to work the way they’re supposed to be working,” Butz explains.Their recommendation is to start with products less likely to drift and use a drone in scenarios or situations that are less sensitive.
A Tool Worth Trying
Like with all new technology, drone sprayers will no doubt have to earn their stripes. For farmers such as Patrick, it’s just another tool to deploy when the situation is right, such as when the aphids are going crazy on his sorghum but it just rained 2″ and he can’t run a sprayer.Today, he does not see this technology replacing the pre- or post-emerge passes on his operation.“However, at the end of the year, if you don’t want to run over a bunch of crops to spot spray, I think drone sprayers are definitely a tool we can use,” he says.“There’s a definite fit for these drones,” Young agrees. “It can allow us to be more timely with some of our pesticide applications and for us to be better stewards of pesticides.”
Scale insects are a diverse group of small, sap-sucking insects with flat or domed shells. Their lack of mobility and protective shell make them difficult to manage. This explains why many scale species are commercial agricultural pests. Scales pierce plant tissue with their mouthparts to feed on the sap weakening the plant. Any excess fluid is secreted as honeydew, a sticky liquid which is often colonised by sooty mould (Ascomycete fungi species).
Cottony cushion scale (Icerya purchasi) on a Trident maple (Acer buergerianum) branch in Fremont, California. Photo by: Derell Licht (Flickr).
Pests of fruit trees
There are over 8000 described scale insect species. They are small, herbivorous, sap-sucking insects with extreme sexual dimorphism (there are vast differences between males and females). Females tend to be soft-bodied with no limbs and are protected by a domed shell. Males are more like flies, with legs and sometimes wings.
Some scale species are serious commercial pests, particularly of nut and fruit trees. A few examples include:
Red scale (Aonidiella aurantia) is a severe pest of citrus in the USA, Southern Africa, Australia and New Zealand, Mexico, much of South America, Israel and the eastern Mediterranean.
Native to Australia, the Cottony cushion scale (Icerya purchasi) has become widely spread throughout most of the tropical and sub-tropical countries of the world. It has also become established in southern Europe. It is a pest of citrus as well as other fruit and ornamental trees.
The San José scale insect (Diaspidiotus perniciosus) is a pest of several fruit tree species, including peach, pear, apple and plum. This species originates from eastern Asia but has spread to North and South America, New Zealand and northern Europe.
Management of scale insects: Prevention
To prevent initial infestations, purchasing certified nursery stock that is free of scales is very important.
Maintaining natural predator populations is vital for preventing scale populations from reaching a stage where they are causing significant damage. The most important natural enemies (or predators) of scale insects are ladybird beetlesand green lacewings. The main parasitoids of scale insects are chalcidoid wasps. To maintain these populations, avoid using broad-spectrum insecticides and intercrop or plant attractive flowering plants to improve diversity.
In addition, ants protect scales from their natural enemies, so maintaining their local population is imperative. Removing weeds from between trees or planting ant-repellent plants like mint and cinnamon can help to reduce the ant population.
To prevent spreading scales further, clean equipment with water and check clothing before moving between areas with and without scale infestations.
Female scales only tend to move very short distances during their lives. Pruning annually can help to prevent trees from touching and therefore reduces tree-to-tree spread of scales. And when pruning, burn or bury the diseased and dried branches.
Maintaining healthy plants helps to reduce their susceptibility to scale damage. Using recommended fertilizer rates and irrigation schedules is important to keep trees as healthy as possible.
Carpenter ants (Camponotus spp.) tending scale insects in Virginia, USA. Photo by: Judy Gallagher (Flickr).
Management of scale insects: Symptoms
Due to their small size and often cryptic behaviours, they can be difficult to observe until they cause significant damage.
Scale insects tend to attack young shoots and fruits of fruit trees. Particularly citrus, apple, peach, pear and plum species. The plant generally becomes weaker with fewer leaves and buds, and honeydew can form a crust on branches and stems. Although these are the generic symptoms caused by scale insects, there is some variation depending on the species. For example:
Symptoms of red scale: yellow halos around scales’ feeding points and excreted honeydew. Heavy infestations can cause leaves to wilt and fall prematurely, dieback of twigs and branches, deformed and dropped fruits, and stunted growth in young trees.
Symptoms of cottony cushion scale: large quantities of honeydew, fruit drop, wilting leaves, defoliation, and dieback of twigs and small branches.
Symptoms of San José scale: red spots on the fruit (known as ‘chilindrina’), yellowing of the leaves and defoliation. Heavy infestations can cause branches to die and the tree to lose its vigour.
Management of scale insects: Monitoring
To monitor for scale insects during the dormant season, observe fruit trees every week. Look for the presence of scales, black sooty mould growing on excreted honeydew or small holes caused by parasitoids. Inspect approximately 5 trees per hectare, checking 5-10 twigs or branches per tree. If more than 5-10% of the sampled trees are infested, take direct control measures.
During the growing season, monitor for the movement of winged males and parasitoids using sticky traps or pheromone traps. Also, monitor weekly for the symptoms previously mentioned.
Management of scale insects: Direct control
Insecticides tend to be ineffective due to scales’ shell and waxy covering. Instead, mineral oil in contact with the scales’ shell prevents the insect from breathing and it dies. Mineral oil, like Triona 5, should be applied at the beginning of the cycle. Trees are sensitive to the oil, and if applied when plants are sprouting, flowering or fruiting, the fruit or flowers may fall. Follow the instructions on the label of the product.
There are several types of species which can be used for biocontrol of scale insects. Check with the Ministry of Agriculture in your country for local recommendations for biocontrol and consider advice from local extension officers. In tropical regions, parasitic wasps like Metaphycus luteolus and parasites like Aphytis lignanensis can be successful when released locally. Whereas in temperate conditions, A. melinus may be more suitable. Finally, in arid and hot inland areas where insecticides aren’t over-used, the Vedalia beetle (Novius cardinalis) is commonly used.
Ant populations should be controlled to prevent them from protecting scales from their natural enemies. Sticky barriers around tree trunks can be created using duct tape or fabric tree wrap coated with a sticky substance like Tanglefoot on infested trees. Double-sided sticky tape can also be used on branches. The barriers should be checked every week or two, and any debris that builds up should be removed to prevent ants from crossing the barrier.
During the summer, remove any infested branches, leaves or fruit to isolate the damage. Burn the infested plant material, or bury it at least 20cm deep.
Further reading
If you would like to find more information on this subject, please see the links below:
For a wide range of resources relating to scale insects, including country and species-specific information, try this PlantwisePlus Knowledge Bank search
Responsible use of pesticides depends in part on understanding where and when they’re used and their impacts on the environment. However, a key source of information on pesticide usage is being scaled back, which could leave scientists and the public in the dark. Just one example of research using data from the U.S. Geological Survey Pesticide National Synthesis Project is a 2023 study linking population declines in the bumble bee Bombus occidentalis to usage of neonicotinoid pesticides. (Photo by Casey Delphia, Ph.D., Montana State University)
By Maggie Douglas, Ph.D.
Imagine public health workers trying to manage the spread of disease without information on where infection rates are highest or how they are changing week-to-week. Or scientists and policymakers attempting to understand and mitigate climate change without monitoring the concentration of greenhouse gases in the atmosphere. This specter is all too real for those of us studying and managing pesticide use and its effects, who are facing the slow disappearance of a critical resource: the U.S. Geological Survey Pesticide National Synthesis Project.
For over a decade, this USGS program has published datasets, maps, and graphs describing the use of agricultural pesticides in U.S. states and counties on an annual basis back to 1992. At its most complete, the dataset reported hundreds of chemicals spanning pest targets (insecticides, fungicides, and herbicides) and covering virtually all U.S. cropland, making it the single most comprehensive description in the country of which pesticides are applied where and when. Even if you aren’t familiar with the name of the project, you may have seen one of their now-ubiquitous maps or graphs, which are frequently used in news stories.
However, in recent years, this invaluable resource has been reduced in size, scope, and detail, and more cuts are looming. Scientists in a variety of fields, including entomology, are concerned.
The USGS program has also become a central resource for education, outreach, and agricultural extension related to pesticides. More than a hundred organizations working on issues ranging from insect conservation to IPM to farmworker health recently signed a letter expressing their dismay about the degradation of the program, which they described as “one of the most vital tools for monitoring pesticide use and estimating water pollution nationwide.” The Entomological Society of America, meanwhile, has been in contact with Congress, federal agencies, and other societies regarding the issue.
The maps and graphs published by the USGS are frequently used in a wide array of venues to demonstrate how pesticide use varies in space and time. As just one example, Anders Huseth, Ph.D., assistant professor and extension specialist in entomology at North Carolina State University, uses the maps to help farmers understand how to prevent insecticide resistance and to communicate to IPM students how pesticide use varies across the U.S. landscape.
In recent years, the data available in the USGS Pesticide National Synthesis Project has been reduced, as these examples illustrate. Top row: The insecticide clothianidin is primarily used as a seed treatment. At left is the map showing the estimated use pattern in 2014, while at right is what the map looked like after seed treatments were no longer included in the dataset in 2015. Bottom row: The common insecticide bifenthrin is used in corn, soybeans, cotton, wheat, and fruits and vegetables, among other crops. The map at left shows its use pattern in 2018; as illustrated at right, this information was entirely absent after bifenthrin was dropped from the dataset in 2019. (Images downloaded from the USGS Pesticide National Synthesis Project by Maggie Douglas, Ph.D.)
Cutbacks Leave a Huge Gap
Unfortunately, the scaling back of the USGS program has radically reduced its value to the scientific community, educators, diverse organizations, and the public—and further cuts are in progress.
In 2015, the dataset stopped including seed-applied pesticides, one of the most widespread methods of application, and one that is not reported anywhere else. In 2019, the scope narrowed further to track only 72 pesticides, reducing the number of tracked chemicals by roughly 80 percent and the amount applied by 40 percent. Recently, the agency announced that, after 2024, the data will only be updated every five years, a significant lag given how quickly the pest management landscape changes.
The reasons for the cutbacks are still not entirely clear. Funding constraints are an obvious hypothesis but do not seem to be the full explanation. The data at the heart of the program come from farmer surveys administered by a private research firm, which are then purchased and processed by USGS into the dataset it provides. Public records show that the raw data cost USGS no more than $150,000 per year at its height, a tiny fraction of the agency’s current $1.7 billion annual budget and a modest price tag for this invaluable information.
Whatever the underlying reasons, these losses of pesticide usage data leave scientists and the public in the dark.
What You Can Do
No matter your perspective or role, you can speak your mind about the value of Pesticide National Synthesis Project:
Contact your Congressional representatives. Encourage them to write a letter to USGS requesting an explanation for the cutbacks and expressing support for restoring the program. (For guidance, see this shared document with talking points and Congressional contact info.)
If you use the Pesticide National Synthesis Project maps, graphs, or data in your work, please fill out this brief survey by July 3. Responses will aid in demonstrating the value of the program and what stands to be lost if it is not reinstated.
Spread the word. Contact the organizations you belong to and encourage them to engage in support of the Pesticide National Synthesis Project. Many organizations have policy arms that may be in a good position to advocate for the program.
Thank you for speaking out to restore this essential pesticide database!
Maggie Douglas, Ph.D., is an assistant professor of environmental science at Dickinson College in Carlisle, Pennsylvania. Email: douglasm@dickinson.edu.
Kenyan Papaya Farmers Willing to Reduce Pesticide Use: Study
Mirage News
CABI
A new study published in the CABI Agriculture and Bioscience journal has revealed a willingness of smallholder papaya farmers in Kenya to reduce their chemical pesticide use to fight the papaya mealybug (Paracoccus marginatus).
Researchers from CABI surveyed 383 farming households in four counties in Kenya alongside key informant interviews with eight extension agents and thirty agro-dealers, and eight focus group discussions.
They found that in a desperate attempt to control invasive alien pests’ farmers often resort to the use of broad-spectrum insecticides even though biological control is a more sustainable method of pest management that is extremely suitable in the smallholder production context found in Sub Saharan Africa (SSA).
Kate Contstanine, Project Scientist at CABI and lead author of the study, said, “In SSA few attempts using biological control for arthropod pests have been successful, with one of the key reasons cited as poor involvement of farming communities and extension in the dissemination of information.
Many potato growers rely on nematicides to protect their crops. Following is information you should know about both fumigant and non-fumigant methods.
Fumigant Nematicides
Although you apply fumigant nematicides, like 1,3-dichloropropene (Telone II) and metam sodium (Vapam HL), to soil in liquid form, it vaporizes and diffuses through the soil as a gas. They are applied before planting.
Nematodes absorb fumigant nematicides through their body cavities, so ingestion isn’t necessary. They work best when nematodes are exposed to a lethal dose for as long as possible. Control failures often relate to poor dispersion or retention of the fumigant gas or failing to place the product where needed.
Here’s how to maximize dispersion and retention of fumigant nematicides.
Clear the soil of clods and compacted areas before application. Incorporate plant residues thoroughly and lay those on the soil surface flat to permit effective soil sealing. Soil temperature at the depth of application should be between 40°F and 80°F.
Generally, maintain soil moisture close to 80% of available water capacity, but recommendations vary depending on site-specific factors (soil texture, water availability, and weather — especially potential for rain).
Product labels are full of guidance on these points. Follow directions closely to enhance the effectiveness of fumigant applications.
If the fumigant does not contact nematodes, it will not control them.
Pay attention to soil moisture and temperature. The more mobile nematodes, especially stubby root nematodes, will move deep into the soil to avoid conditions that are too hot, cold, or dry.
Applying metam sodium with overhead sprinklers does not usually push the product deep enough to reach nematodes. This method works better for controlling weed seeds and fungal pathogens near the soil surface. Instead, inject fumigants using shank implements with attached spray nozzles at a depth of 14 to 16 inches to contact nematodes. Make sure you use the typically recommended higher rates for targeting nematodes.
Non-fumigant Nematicides
The most commonly used non-fumigant nematicides in potatoes are ethoprop (Mocap), oxamyl (e.g., Vydate, Return), fluensulfone (Nimitz), and fluopyram (Velum Prime). These are granule or liquid products that percolate down through the soil in water. They are soil-applied, pre-plant or at planting, except for oxamyl and fluopyram, which may also be applied to the foliage in-season.
These products aren’t true nematicides because they do not kill nematodes immediately on contact. Instead, they have a “narcotic” effect on nematodes, temporarily paralyzing them, stopping feeding, and delaying egg hatch and molting.
These effects can be lethal if you maintain nematicide concentrations at high levels for an extended time, leading to death from starvation or poisoning. But they can also be reversed if exposure is short and/or at low concentrations.
The efficacy of non-fumigant nematicides largely depends on their solubility in water and persistence in the soil. Products that are highly soluble, like Vydate, Mocap, and (to a lesser extent) Nimitz, are mobile in the soil and distribute effectively to contact nematodes, but they can move out of the root zone with excess rainfall or irrigation.
Oxamyl breaks down rapidly in soil, so it doesn’t last long even when it isn’t leached. This is one reason why an in-furrow application of Vydate at planting must be followed with several foliar applications to achieve full season nematode suppression.
In fact, using a soil degree-day model can optimize the timing of in-season Vydate applications for controlling root-knot nematodes (it involves logging soil temperature at a 6- to 8-inch depth). The model estimates when juvenile nematodes will be present, which is helpful because juveniles are the most susceptible developmental stage of this endoparasite nematode to target with nematicides.
Ethoprop only persists in the soil for about 5 to 6 weeks, so Mocap is not recommended for severe nematode infestations of long season potatoes unless it is followed up with another nematicide.
Growers who opt to apply oxamyl, the most widely used of the non-fumigant nematicides, should know that use instructions differ depending on your region, the species of nematode targeted, and severity of nematode infestations. Study the Vydate or Return label carefully to comply with these important site-specific instructions.
The in-furrow application of oxamyl products is said to be optional, but growers should carefully consider the risks before they opt out of this application. Many nematode species are particularly active when potato roots and tubers are in their early growth phases. In fact, stubby root nematodes may not be effectively controlled if the first oxamyl application isn’t made before tuber initiation. In other words, more foliar applications will not make up for not applying oxamyl earlier.
Disclaimer: Application of a pesticide to a crop or site that is not on the label is a violation of pesticide law and may subject the applicator to civil penalties. It is your responsibility to ensure lawful use and obtain all necessary permits in advance of application.
Source: American Vegetable Grower. Original article here Cover image:Globodera pallida cyst. Wikimedia Commons. Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services Author: Carrie Huffman Wohleb is Associate Professor/Regional Specialist – Potato, Vegetable, and Seed Crops, at Washington State University.
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Harnessing research to speed up the agroecological transition aligns with the objectives of the European Green Deal and addresses the strong demand from public authorities, stakeholders and society at both the national and European levels. For more than two years, over 144 experts investigated possible ways to eliminate pesticides from agriculture on a European scale for the “European Pesticide-Free Agriculture in 2050” foresight study. The three scenarios that were explored to promote changes in the agricultural and food system were presented during a symposium to discuss the findings. Some 1,4200 participants of 64 different nationalities attended the conference on Tuesday 21 March in Paris, where remarks were heard from various French and European stakeholders in the fields of agriculture, regulation and policymaking, environment, and food. This groundbreaking attempt to weave together a larger narrative was bolstered by measured impacts on European food sovereignty and the environment for each scenario. Possible pathways forward are given for each scenario for the European and regional transition of the entire food system based on participatory workshops conducted in four regions in Italy, Romania, Finland and France.
While the negative impacts of chemical pesticides on the environment and human health are well documented, European policies are struggling to make progress towards the target of cutting chemical pesticide use by 50% [1] by 2030. This observation spurred 144 experts, scientists and stakeholders to work together for two years to produce a foresight study that sought to change the model and design agricultural and food systems without any chemical pesticides by 2050.
Chemical pesticides are essential in today’s conventional agricultural systems. Drastically reducing their use to the point of completely eliminating them from agriculture is a thorny issue for which there is no simple solution. This foresight study goes further in terms of the ultimate goal and time frame by asking whether effective crop protection in pesticide-free agriculture is feasible in Europe by 2050 and how to transition to this type of agriculture. Under what conditions would such a transformation be possible? What would the impacts be on production, land use, the trade balance and greenhouse gas emissions? This foresight study, conducted as part of the “Growing and protecting crops differently” Priority Research Programme (PPR) and in conjunction with the “Towards a Chemical Pesticide-Free Agriculture” European Research Alliance,[2] aims to shed light on all these issues and to suggest pathways forward. It offers three scenarios of pesticide-free agriculture for Europe in 2050, each with a transition pathway and examples of these scenarios and pathways in four European regions, along with a quantitative evaluation of their impacts in Europe:
Scenario 1: “Global market”: global and European food value chains based on digital technologies and plant immunity for a pesticide-free food market.
Scenario 2: “Healthy microbiomes”: European value chains based on plant holobiont, soil and food microbiomes for a healthy diet.
Scenario 3: “Embedded landscapes”: complex and diversified landscapes and regional food value chains for a one-health food system.
For each scenario, pesticide-free cropping systems make use of crop diversification, biocontrol development, the choice of suitable crops and varieties, digital technology and agricultural equipment, and monitoring systems to anticipate the arrival of pests.
Differentiated impacts measured for each scenario
One of the key aspects of this foresight study is that it quantified the impacts of each scenario on agricultural production, land use, greenhouse gas emissions and trade, based on the results of simulations of a biomass equilibrium model at the European and global scales.
With regard to European agricultural production, calorie production varies from −5% to +12% depending on the scenario, with a balance to be struck between reducing the consumption of animal products and maintaining grasslands. In terms of the trade balance, the overall impact of scenarios 2 (Healthy microbiomes) and 3 (Embedded landscapes) gives Europe room for manoeuvre to secure its food sovereignty and export its products. The three scenarios reduce greenhouse gas emissions by −8% (scenario 1), −20% (scenario 2) and even up to −37% (scenario 3). All three pathways lead to an increase in the carbon stock in soils and biomass, which will contribute to carbon neutrality by 2050 for the agricultural and agri-food sector in scenarios 2 and 3.
The keys to success: coherent European public policies, the involvement of all value-chain players and risk sharing among stakeholders
Effective crop protection without chemical pesticides relies on several levers that must be activated in tandem: crop diversification over time and across space, the development of biocontrol products and biological inputs, appropriate varietal selection, farm equipment and digital tools, and tools for monitoring pest dynamics and the environment. Biological regulation mechanisms at the soil, field and landscape levels should be favoured, as well as preventive measures gainst pests.
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Specific case studies in Italy, Romania, Finland and France helped establish transition pathways that showed that the entire food system must be considered in this redesign and involve all players across the chain, from producers to consumers who must change their diets and authorities responsible for public and regulatory policies. Transitioning to chemical pesticide-free agriculture will require a coherent mix of European public policies to reduce pesticide use articulated with other policies such as food policies, support the transition through a redesign of the Common Agricultural Policy (CAP) and economic instruments that can be leveraged, and create pesticide-free markets through trade agreements. Finally, the transition will need the various stakeholders to share the risk of transforming their cropping systems and the agricultural and agri-food supply.
The scenarios explored in the foresight study should help decision-makers and the scientific community to identify new research avenues to build a future chemical pesticide-free European agricultural and agri-food system by 2050.
This article has been republished from the following materials. Note: material may have been edited for length and content. For further information, please contact the cited source.
Drone-driven sprayers are popping up across the country as better batteries, longer flight times and bigger machines make it possible to spray sizable acreage in a timely manner.“There’s a 10-gal. tank so every 5 acres he has to come back to refill,” Patrick explains. “We knocked out 150 acres in about four to six hours.”
“I think Kyle and I both asked the same question: On what basis are they deciding where to put the nozzles?” Gunasekaran recounts. “It turns out, they just take an agriculture nozzle, stick it underneath the propeller and then go fly without understanding the aerodynamics or the right location for that nozzle.”In search of answers, Gunasekaran and Butz developed a test rig with two propellers, a spray nozzle and a measurement system. They confirmed the propellers do in fact pull droplets back into the down draft while blowing smaller droplets out away from the target zone.“If you have smaller droplets, called fines, which are anything under 140 microns, they are prone to drift,” Gunasekaran says.From a sprayer’s perspective, however, there’s always been a balancing act between droplet sizes and efficacy.“Ultimately, spray applications come down to, one, droplets have to be large enough to safely reach the target, and two, they have to be small enough to work the way they’re supposed to be working,” Butz explains.Their recommendation is to start with products less likely to drift and use a drone in scenarios or situations that are less sensitive.
Global Plant Protection News 