Foliar Insecticide Applications Research Articles

Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides.

Conservation of North America's eastern monarch butterfly (Danaus plexippus) population would require establishment of milkweed (Asclepias spp.) and nectar plants in the agricultural landscapes of the north central United States. A variety of seed-treatment and foliar insecticides are used to manage early- and late-season pests in these landscapes. Thus, there is a need to assess risks of these insecticides to monarch butterfly life stages to inform habitat conservation practices. Chronic and acute dietary toxicity studies were undertaken with larvae and adults, and acute topical bioassays were conducted with eggs, pupae, and adults using 6 representative insecticides: beta-cyfluthrin (pyrethroid), chlorantraniliprole (anthranilic diamide), chlorpyrifos (organophosphate), imidacloprid, clothianidin, and thiamethoxam (neonicotinoids). Chronic dietary median lethal concentration values for monarch larvae ranged from 1.6 × 10-3 (chlorantraniliprole) to 5.3 (chlorpyrifos) μg/g milkweed leaf, with the neonicotinoids producing high rates of arrested pupal ecdysis. Chlorantraniliprole and beta-cyfluthrin were generally the most toxic insecticides to all life stages, and thiamethoxam and chlorpyrifos were generally the least toxic. The toxicity results were compared to insecticide exposure estimates derived from a spray drift model and/or milkweed residue data reported in the literature. Aerial applications of foliar insecticides are expected to cause high downwind mortality in larvae and eggs, with lower mortality predicted for adults and pupae. Neonicotinoid seed treatments are expected to cause little to no downslope mortality and/or sublethal effects in larvae and adults. Given the vagile behavior of nonmigratory monarchs, considering these results within a landscape-scale context suggests that adult recruitment will not be negatively impacted if new habitat is established in close proximity of maize and soybean fields in the agricultural landscapes of the north central United States. Environ Toxicol Chem 2021;40:1761-1777. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Cotton Fleahopper1 Biology and Ecology Relevant to Development of Insect Resistance Management Strategies

Since the success of the U.S. Boll Weevil Eradication Program and widespread adoption of genetically modified crops, the cotton fleahopper, Pseudatomoscelis seriatus (Reuter), has reemerged as a significant cotton pest. Current management strategies for the pest are based primarily on foliar applications of insecticides. A line of cotton that produces modified Bt Cry51Aa2 protein was developed for Lygus spp., but the protein has also shown activity against the cotton fleahopper. Consequently, before this new Bt line can be released commercially, refuge requirements and other Insect Resistance Management (IRM) strategies mandated by the Environmental Protection Agency need to be established to prevent or delay development of resistance by cotton fleahopper to the new toxin. In response, we provide and discuss relevant information on the biology and ecology of the cotton fleahopper, including life history, host preference, dispersal, and population genetic structure, that may be useful for developing IRM strategies for the pest.

Current Advances in Biology, Distribution, and Management of Melanaphis sacchari (Zehntner)1 in México and United States of America

The sugarcane aphid, Melanaphis sacchari (Zehntner), is a major insect pest of sorghum (Sorghum bicolor (L.) Moench) in Mexico and United States of America. This review reports current advances for the biology of the aphid, crop damage, and sampling strategies to detect the pest. We focused on management through cultural control including resistant varieties, biological control with native parasitoids and predators and use of entomopathogenic fungi, legal control, and chemical control. Life stages of the aphid are nymph, nymphal alate, super nymph, and adult. Females have parthenogenetic reproduction and under adverse conditions, viviparous reproduction. Damage to the sorghum crop by feeding nymphs and adults causes stress to the plants and yield loss. To detect the pest, leaves should be sampled each week or yellow traps used with soapy water to monitor arrival of winged adults. Cultural practices recommended are destroying foci of infection and using established official planting dates and appropriate fertilization. Currently, the main control strategy is foliar application of insecticides. However, numerous species of predators, parasitoids, and entomopathogenic fungi affect sugarcane aphids in the USA and Mexico. The organisms could sustain control of the aphid, but few have been evaluated in the field. Studies of sorghum varieties in areas of México and the USA allowed identification of genotypes with resistance to sugarcane aphids. Considering sampling strategies, biology, and life cycle studies, search for an organism with potential for biological control of M. sacchari, and identification of sorghum genotypes with resistance to damage, it is possible to develop an integrated management strategy against sugarcane aphid. For future research, it is important to develop bioassays for monitoring resistance to insecticide, study interaction between factors that favor natural and induced control with natural enemies, and promote planting of sorghum genotypes with resistance.

Evaluation of flupyradifurone for the management of the Asian citrus psyllid Diaphorina citri via dripping irrigation systems.

Chemical control is the most used and effective method to control Diaphorina citri, the vector of the phloem-limited bacteria associated with citrus huanglongbing (HLB) disease. The objectives of this study were to determine the effectiveness of flupyradifurone applied via dripping irrigation systems on D. citri. Bioassays were conducted using leaves harvested on various dates post treatment, and insecticide residue in leaf tissue was quantified. The drip application of flupyradifurone on citrus trees provided high-level and long-term control against D. citri adult, and the median lethal concentration (LC50 ) for ingestion of flupyradifurone in D. citri was 22.22 mg kg-1 (fresh leaf). Flupyradifurone residue was detected in leaf tissue within 3 days after treatment. The measured level of flupyradifurone peaked on day 40 day after application, and then showed a steady decline in subsequent days for all three applied dosages. The amounts of flupyradifurone in upper, middle, and lower leaves were similar, and trends in the change in concentration of flupyradifurone were consistent. The results demonstrate that flupyradifurone can be a valuable new tool for D. citri management programs, and drip-applied flupyradifurone provides an extended period of control efficacy. This paper could provide a reference to reduce the dependence on foliar-applied insecticides, with associated benefits for non-target exposure to workers and pollinators. © 2021 Society of Chemical Industry.

Foliar application of systemic insecticides disrupts feeding behavior of the whitefly Bemisia tabaci MEAM1 and the transmission of tomato chlorosis virus in potato plants

The whiteflies of the Bemisia tabaci (Genn.) complex (Hemiptera: Aleyrodidae) are serious agricultural pests that cause severe losses to vegetable, ornamental and fiber crops, including potato plants, mainly as a vector of economically important viruses. Among the most important viruses affecting potato is tomato chlorosis virus (ToCV) (Closteroviridae: Crinivirus), which is semi-persistently transmitted by whiteflies of the genera Bemisia and Trialeurodes. Chemical control is the main method used to manage B. tabaci and ToCV; however, this whitefly is resistant to most commercially available insecticides, and some products may not effectively prevent the vector stylet activities associated with virus transmission. The effective management of B. tabaci is crucial to reduce the spread of vector-borne diseases, and to minimize economic losses. We evaluated the effects of the foliar spraying with the systemic insecticides acetamiprid, flupyradifurone and cyantraniliprole on the probing behavior of non-viruliferous and ToCV-viruliferous B. tabaci MEAM1 and ToCV transmission in potato plants. To evaluate ToCV transmission in greenhouse conditions, viruliferous whiteflies were released on potato plants at different time points (3, 24 and 72 h and 7 days) after insecticide spraying. The EPG assay showed that at 3 h after insecticide application, the probing behavior differed, depending mainly on the state of the insects (viruliferous or not), whereas 72 h after application, the probing behavior differed only on plants treated with acetamiprid and flupyradifurone, for both viruliferous and non-viruliferous whiteflies. ToCV transmission was reduced mainly in plants treated with flupyradifurone and acetamiprid, likely as a result of phloem activity disruption.

Evaluation of Insecticidal Seed Treatments and Foliar Applied Insecticides Against Rice Billbug in Louisiana Row Rice, 2020

Evaluation of Insecticidal Seed Treatments and Foliar Applied Insecticides Against Rice Billbug in Louisiana Row Rice, 2020

Needs Assessment for Corn Insect Pest Management in Iowa

AbstractCorn, Zea mays L. (Cyperales: Poaceae), production is essential to Iowa’s economy and provides food, feed, and fuel beyond the state. Farmers face a number of challenges in corn production, including insect pests, and understanding farmers’ perceptions and concerns is critical for extension personnel to provide adequate and relevant programming. The Iowa State University Agriculture and Natural Resources Crops Team conducted a survey of Iowa farmers and agribusiness professionals during the 2019–2020 extension season. The goal was to understand farmer perceptions of corn pests and whether farmers experienced challenges with resistance to Bt traits or insecticides. Additionally, we aimed to realize farmers’ confidence in developing resistance management plans and discussing those needs with their input suppliers and advisors. Our survey revealed that northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), was the pest of greatest concern across the state. People were generally more concerned about belowground Bt trait performance than aboveground traits, though only 12% of respondents reported Bt trait failure for corn rootworms. In general, people were not concerned about the performance of seed treatments or soil- or foliar-applied insecticides. Farmers generally felt very confident in developing a resistance management plan and discussing their needs with their advisors. The results of this survey will be used to target extension programming throughout the state and increase confidence for farmers and agribusiness employees to discuss resistance management plans together.

Fungicide, insecticide, and foliar fertilizer effect on soybean yield, seed composition, and canopy retention

AbstractSoybean [Glycine max (L.) Merr.] yield has increased over time through the introduction of new varieties and improved agronomic practices. However, seed protein concentration has decreased. We conducted field studies in 2018 and 2019 to investigate the effects of fungicide, insecticide, and foliar fertilizer application on grain yield and seed quality in two soybean maturity groups (MG). In‐season treatments targeted nutrient availability and soybean canopy duration during the seed‐filling period by fungicide, insecticide, or foliar fertilizer application at the onset of this period. Biomass samples were collected at R5, R6, and R7 and partitioned into plant parts. Year, location, and MG often influenced yield and seed composition, but foliar fungicide, insecticide, or fertilizer application had no impact on these parameters.

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2020

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2020

Developing a Residual Testing Protocol for Soybean Aphid (Hemiptera: Aphididae)

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), continues to be an economically important insect pest of soybean in the northcentral region of the United States since its first report in 2000. Control has traditionally relied on foliar applications of pyrethroid and organophosphate insecticides; however, recent confirmed failures of pyrethroids in the region have prompted immediate management concerns. Insecticidal modes of action are limited, and there is a need for assessing residual efficacy of exisiting and new insecticides for soybean aphid. We developed a field-based protocol to evaluate the residual efficacy of treated foliage, and tested our method with two insecticides. Our residual testing protocol can be utilized for residual efficacy evaluations of other pests and in other systems.

Comparison of chemigation versus foliar insecticide use: management of lepidopteran larvae and stink bugs in North Carolina field tomatoes with environmental and farmworker benefits

Commercial vegetable production in the United States of America (USA) often relies on foliar insecticide sprays for managing key insect pests. However, foliar applications of insecticides have a number of drawbacks to the health of consumers, farmworkers and the environment. Drip chemigation is the application of pesticides to the soil through trickle (drip) irrigation systems, and can overcome a number of the drawbacks typical of foliar insecticide applications. We conducted a two-year study in five commercial fields of staked tomatoes in western North Carolina to compare the efficacy, economics and environmental impact of drip chemigation versus foliar sprays. Drip chemigation significantly reduced insecticide inputs, utilized more selective and environmentally compatible insecticides, and reduced the time lost to reentry intervals, while maintaining comparable efficacy and economic returns. Drip chemigation was an effective tool for managing key insect pests, provided a broad range of human and environmental health benefits, and will likely become increasingly cost-effective in the future as insecticide patents expire and more insecticide options become available.

Managing Allium Leafminer (Diptera: Agromyzidae): An Emerging Pest of Allium Crops in North America.

Allium leafminer, Phytomyza gymnostoma Loew, is the newest invasive pest of allium crops in North America. Larvae initially feed in the upper canopy before mining toward the base of the plant to pupate. Crop loss occurs when larvae destroy vascular tissue, facilitating infection by bacterial and fungal pathogens that cause rot. Contamination also occurs when larvae and pupae are present at harvest. In response to this invasion, efficacy of 14 insecticide active ingredients applied via foliar sprays, transplant treatments, and drip chemigation was evaluated for managing P. gymnostoma. Multiple field studies were conducted in onions, leeks, and scallions in Pennsylvania and New York, United States in 2018 and 2019. The highest and most consistent levels of P. gymnostoma control occurred using foliar applications of dinotefuran, cyantraniliprole and spinetoram (84-89% reduction in damage; 95% reduction in P. gymnostoma densities). Despite the success of dinotefuran and cyantraniliprole applied as foliar sprays, neither was effective in controlling P. gymnostoma when administered via drip chemigation. Other foliar-applied insecticides that significantly reduced densities of P. gymnostoma in one or two experiments included abamectin, acetamiprid, cyromazine, imidacloprid, lambda-cyhalothrin, methomyl, and spinosad. Active ingredients that never controlled P. gymnostoma included azadirachtin, kaolin clay, pyrethrin, and spirotetramat. Spinosad applied to bare-root and plug-tray transplants immediately before transplanting reduced P. gymnostoma damage in the field by >90%. Implications of using these insecticides and application strategies are discussed within the context of developing a sustainable IPM program.

Control of Diamondback Moth on Broccoli with Foliar Applied Insecticides, 2019

Control of Diamondback Moth on Broccoli with Foliar Applied Insecticides, 2019

Efficacy Foliar Applied Insecticides on Tobacco Budworm in Flue-Cured Tobacco, 2020

Efficacy Foliar Applied Insecticides on Tobacco Budworm in Flue-Cured Tobacco, 2020

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Combining host plant resistance and foliar insecticide application to manage Melanaphis sacchari (Hemiptera: Aphididae) in grain sorghum

Sugarcane aphid, Melanaphis sacchari (Zehtner), recently emerged as a severe economic pest of sorghum in the USA. This insect was first discovered in the USA feeding on grain sorghum in Texas in 2013 and then rapidly spread across 19 additional states. In order to develop management practices to prevent yield loss, the objective of this study was to assess the value of host plant resistance and foliar applications of insecticide in five commercially available grain sorghum hybrids, across five locations in the southeastern USA. Field experiments were conducted in 2017 in Tift, Peach, and Pike Counties in Georgia; Barbour County in Alabama; and Darlington County in South Carolina. Foliar flupyradifurone applications were initiated at the action threshold of 50 aphids per leaf for each hybrid. Grain sorghum hybrids ‘DKS48-07’ and ‘DKS37-07’ showed resistance to M. sacchari across study locations. The most resistant variety, ‘DKS48-07’, required no foliar insecticide. Conversely, hybrids ‘KS585’ and ‘DKS53-53’ were highly susceptible. A single foliar application of flupyradifurone immediately suppressed M. sacchari populations and no further treatments were required.

Evaluation of Tactics for Management of Sugarcane Aphid (Hemiptera: Aphididae) in Grain Sorghum.

The invasive sugarcane aphid, Melanaphis sacchari (Zehntner), is a devastating new pest of grain sorghum. Studies were conducted utilizing an integrated approach of four management tactics: planting date, insecticidal seed treatment, a foliar-applied insecticide, and plant resistance. Experiments were conducted in 2016 and 2017 at Griffin, Tifton, and Plains Georgia, and in 2016 in Texas, Alabama, and Oklahoma, United States. Early planting was effective in reducing damage and increasing yields when compared to the late planting. Use of a resistant variety reduced cumulative aphid-days, plant injury and usually prevented significant yield loss. Foliar application of flupyradifurone when aphids reached an economic threshold, was an effective management tactic preventing aphid injury and yield loss. Use of clothianidin seed treatment also reduced aphid injury and yield loss of the susceptible hybrid but generally did not prevent injury and yield loss of the resistant hybrid. We conclude that an earlier planting date coupled with a resistant variety and judicious use of an efficacious foliar-applied insecticide can effectively manage sugarcane aphid on grain sorghum. An insecticide seed treatment also may be useful to reduce the risk of sugarcane aphid damage to seedlings of susceptible hybrids.

Comprehensive Survey of Area-Wide Agricultural Pesticide Use in Southern United States Row Crops and Potential Impact on Honey Bee Colonies.

Honey bees forage across a large area, continually scouting the local landscape for ephemeral food resources. Beekeepers often rely on flowering plants in and around irrigated farmland to maintain their colonies during dry seasons, despite the potential risk of pesticide exposure. Recent declines in pollinator abundance and diversity have focused attention on the role of pesticides and their effects on honey bee health. This investigation examined two types of landscapes within a two-mile (3.2 km) radius of honey bee colonies: an intensive agricultural setting and a rural setting without intensive agriculture. More than 10,000 acres of agricultural land was surveyed to quantify the area of cultivated crops and the area treated with pesticides, including seed treatments and foliar applications of insecticides. Samples of honey, bee bread (stored pollen), beeswax, and adult bees were collected from hives in both landscape types and screened for pesticide residues to determine if foraging bees were transporting pesticides to hives. Some samples of bee bread and honey did contain pesticide residues, but these were below known lethal dose (LD50) levels for honey bees. Beeswax samples contained the highest levels of contamination, but most were still relatively low. Samples were screened for 174 common agricultural pesticides and metabolites, but only 26 compounds were detected during the two-year study. These included one defoliant, one insect growth regulator, five herbicides, six fungicides, six insecticides never used in beekeeping, and five insecticides/miticides and their metabolites, which are used in beekeeping and for various other agricultural purposes, as well as two miticides exclusively used by beekeepers to control Varroa destructor. Bee colonies foraging in agricultural landscapes are potentially exposed to numerous pesticide applications. While the residues detected in this study did not pose an acute lethal risk to adult honey bees, this study did not measure sublethal effects on bee colony health or performance, which merit further investigation.

Impact of Simulated Corn Earworm (Lepidoptera: Noctuidae) Kernel Feeding on Field Corn Yield

Corn earworm, Helicoverpa zea (Boddie) Lepidoptera: Noctuidae, has not been considered an economic pest of field corn. Historical losses estimates ranged from 1.5 to 2.5%, and a large number of foliar insecticide applications would be needed to minimize infestations. In recent years, Bt, Bacillus thuringiensis (Berliner) field corn, Zea mays (L.) Poales: Poaceae, technologies that exhibit activity against corn earworm have been introduced. However, it is unclear how much damage to corn ears (number of damaged kernels) is required to reduce yield. In this study manual damage methods were utilized to inflict defined levels of kernel damage and to impose damage at levels greater than observed with natural corn earworm infestations. Bt corn hybrids expressing the Agrisure Viptera (Vip 3A) trait were used to minimize injury from natural infestations of corn earworm. Manual kernel damage was imposed at R3 stage to mimic corn earworm feeding while avoiding interference with pollination. These methods were used in experiments where treatments were applied to individual ears and hand-harvested and in experiments where treatments were applied to all primary ears in the plot and machine-harvested. Damage of ≥60 kernels per ear was required to significantly reduce yield regardless of harvest method. Kernel damage from natural corn earworm infestations reported in other studies was much lower than 60 kernels per ear. Timely planting is a key component of all integrated pest management programs. Field corn planted during the recommended planting window for optimum yield is unlikely to experience corn earworm damage great enough to reduce yield.

Monitoring Onion Thrips (Thysanoptera: Thripidae) Susceptibility to Spinetoram in New York Onion Fields.

Onion thrips (Thrips tabaci Lindeman) is a severe pest of onion (Allium cepa L.). Their management relies on frequent applications of foliar insecticides, including spinetoram (Radiant® SC), which has a novel mode of action and is effective at controlling large populations. However, despite being widely used for the past 10 yr, susceptibility to spinetoram has not been evaluated formally in New York state, where nearly 3,000 hectares of onion are planted annually. Over 2 yr (2017-2018), the susceptibility of onion thrips to spinetoram was assessed from populations collected in commercial onion fields in New York. LC50s for adults were generated from feeding assays and ranged from 2.07 to 5.08 ppm, but grower reports indicate that onion thrips populations continue to be susceptible to spinetoram. Moreover, both regional and temporal variations in susceptibility were similar among these populations based on survival at individual concentrations tested, despite significant differences in LC50s. These results suggest some genetic heterogeneity among onion thrips populations and serve as a valuable reference for the continued monitoring of onion thrips susceptibility to spinetoram, contributing to ongoing efforts to manage insecticide resistance in this system.