Insecticide Inputs Research Articles

Citrus-mediated gene silencing of cytochrome P450 suppresses insecticide resistance and increases mortality in Diaphorina citri.

Asian citrus psyllid, Diaphorina citri, is a hemipteran that vectors the causal pathogen of citrus greening disease, or huanglongbing (HLB). HLB is a tree killing disease that has severely limited citrus production globally. Unfortunately, there is no cure for this disease, and mitigation depends on multiple insecticide applications to reduce vector populations. Silencing of cytochrome P450 expression associated with detoxification enzymes by RNA interference is known to increase susceptibility of D. citri to insecticides. However, dsRNA was previously introduced into psyllids by topical applications. The possible application of this technology for pest management will require effective field delivery of the dsRNA. Therefore, we evaluated a virus vector (Citrus tristeza virus; 'mild strain' T36) to deliver gene silencing directly to this sap-sucking insect via plant phloem. Citrus macrophylla plants inoculated with CTV expressing a truncated consensus sequence of CYP450 (CTV-tCYP450) constantly produced small interfering RNA in the plant phloem that targeted five cytochrome p540 (CYP450) genes in D. citri. Insecticide susceptible D. citri reared on citrus infected with CTV-tCYP450 were subsequently more susceptible to imidacloprid, fenpropathrin, carbaryl, and chlorpyrifos than those reared on citrus infected with wildtype CTV or non-infected negative controls. Additionally, nymph survival and adult lifespan were significantly reduced when psyllids were reared on CTV-tCYP450 citrus plants compared with controls. Interestingly, similar results were obtained after one and two generations of rearing. Finally, field-collected psyllids from areas with known broad-spectrum insecticide resistance were rendered more susceptible to imidacloprid and fenpropathrin after feeding on CTV-tCYP450 citrus trees as compared with those reared on controls. The integration of citrus-mediated RNA inference targeting psyllid detoxification enzymes could function as a resistance management tool and reduce insecticide input in an integrated pest management program for HLB. © 2024 Society of Chemical Industry.

Evaluating neonicotinoid insecticide uptake by plants used as buffers and cover crops

Runoff and drainage from fields planted with neonicotinoid-coated seeds often contain insecticides that adversely affect aquatic life and other non-target organisms. Management practices such as in-field cover cropping and edge-of-field buffer strips may reduce insecticide mobility, making it important to understand the ability of different plants used in these interventions to absorb neonicotinoids. In this greenhouse study we evaluated uptake of thiamethoxam, a commonly used neonicotinoid, in six plant species – crimson clover, fescue, oxeye sunflower, Maximillian sunflower, common milkweed, and butterfly milkweed – along with a native forb mixture and a native grass plus native forb mixture. All plants were irrigated with water containing 100 or 500 μg/L of thiamethoxam for 60 days, then plant tissues and soils were analyzed for thiamethoxam and its metabolite clothianidin. Crimson clover accumulated up to 50% of the applied thiamethoxam, which was significantly more than other plants and indicates this species may be a hyper-accumulator that can sequester thiamethoxam. In contrast, milkweed plants had relatively low neonicotinoid uptake (<0.5%), meaning that those species may not pose excessive risk to beneficial insects that feed on them. In all plants, accumulated masses of thiamethoxam and clothianidin were greater in above-ground tissues (leaves and stems) than in below-ground roots, with more accrual in leaves than stems. Plants treated with the higher thiamethoxam concentration retained proportionally more of the insecticides. Because thiamethoxam primarily accumulates in above-ground tissues, management strategies that include biomass removal may reduce the input of such insecticides into the environment.

The Association of Applied Biology Held a Meeting to Discuss "Bringing Biocontrol and IPM to Market"

Keith Walters welcomed delegates and chaired the first session on "New Solutions", aimed to attract presentations on latest developments and novel Biocontrol/IPM approaches nearing completion or recently launched. Lauren Diepenbrock (University of Florida) started the session in which 'Rebuilding of IPM in growing citrus' was described. Before Huanglongbing (HLG) in the good old days, farmers may have used an oil spray and they used spider webs between trees. HLG is a bacterial disease Liberibacter asiaticus, first detected in 2005 that caused yellow shoots, twig dieback, stunted growth, and overall tree decline with misshapen fruits. Another pest from 1998 was the Asiatic citrus psyllid (ACP – Diaphorina citri) that is the vector of Candidactus liberator, causal agent of HLB. With many natural enemies including ladybirds, lacewings, syrphids, spiders, ants and other parasitoids, but from 1998–2016, in Citrus Health Management areas, farmers used insecticides, including neonicotinoids, but although this achieved solid returns, it was not going to last and there was a need to return to IPM, by incorporating non-insecticidal management options and reduce insecticide inputs. A new tool was to apply kaolin clay to reduce psyllid infestation and increase plant health. Another new idea was to protect individual trees with Exclusion bags to prevent ACP access to trees and improve scouting for pests. While successful with young trees, more research is needed to improve the return on investment.

Impact of Reducing Synthetic Chemical Inputs on Pest and Disease Management in Commercial Onion Production Systems

Onion production is reliant on synthetic chemical inputs such as fertilizer and pesticides to ensure its profitability. In the Great Lakes region (USA), onion thrips (Thrips tabaci) and a complex of bacterial pathogens that cause bulb rot disease threaten the sustainability of onion production. The potential exists for reducing T. tabaci infestations and bulb rot disease incidence in onions by decreasing the amounts of fertilizer applied at planting and the insecticide applied to foliage during the season. In a three-year study that included 20 New York commercial onion fields, the impact of synthetic fertilizer (no fertilizer, half rate, and full rate) and insecticide use (action threshold-based application program and weekly application program) on T. tabaci populations and bulb rot disease incidence was examined. Results indicated that the amount of fertilizer applied to an onion at planting had no impact on T. tabaci population levels, bulb rot disease incidence, or onion bulb size and yield. In contrast, insecticide use had the greatest impact on reducing T. tabaci densities. Both the action threshold-based program and weekly spray program reduced T. tabaci infestation levels below the economic injury level, but the action threshold program averaged 2.3 fewer applications per season. The insecticide program had no effect on bulb rot incidence, bulb size, or yield. We conclude that synthetic fertilizer and insecticide inputs can be reduced substantially without compromising onion bulb yields, and this should lead to greater profits and a reduction of chemicals in the environment.

Nanomaterials for Targeted Delivery of Agrochemicals by an All-in-One Combination Strategy and Deep Learning.

The development of modern agriculture has prompted the greater input of herbicides, insecticides, and fertilizers. However, precision release and targeted delivery of these agrochemicals still remain a challenge. Here, a pesticide-fertilizer all-in-one combination (PFAC) strategy and deep learning are employed to form a system for controlled and targeted delivery of agrochemicals. This system mainly consists of three components: (1) hollow mesoporous silica (HMS), to encapsulate herbicides and phase-change material; (2) polydopamine (PDA) coating, to provide a photothermal effect; and (3) a zeolitic imidazolate framework (ZIF8), to provide micronutrient Zn2+ and encapsulate insecticides. Results show that the PFAC at concentration of 5 mg mL-1 reaches the phase transition temperature of 1-tetradecanol (37.5 °C) after 5 min of near-infrared (NIR) irradiation (800 nm, 0.5 W cm-2). The data of corn and weed are collected and relayed to deep learning algorithms for model building to realize object detection and further targeted weeding. In-field treatment results indicated that the growth of chicory herb was significantly inhibited when treated with the PFAC compared with the blank group after 24 h under NIR irradiation for 2 h. This system combines agrochemical innovation and artificial intelligence technology, achieves synergistic effects of weeding and insecticide and nutrient supply, and will potentially achieve precision and sustainable agriculture.

Future of Insecticide Seed Treatment

Seed treatment as a method of local application of pesticides in precise agriculture reduces the amount of pesticides used per unit area and is considered to be the safest, cheapest and most ecologically acceptable method of protecting seeds and young plants from pests in the early stages of their development. With the introduction of insecticides from the neonicotinoid group in the mid-1990s, the frequency of seed treatment increased. Due to suspected negative effects on pollinators, most of these insecticides are banned in the European Union. The ban has therefore led to a reduction in the number of active substances approved for seed treatment and to an increased re-use of active substances from the group of pyrethroids as well as other organophosphorus insecticides, which pose potentially very serious risks, perhaps even greater than those of the banned neonicotinoids. The objective of this review is to analyze the advantages and disadvantages of seed treatment and the potential role of insecticide seed treatment in reducing the negative impact of pesticides on the environment. The main disadvantage of this method is that it has been widely accepted and has become a prophylactic protective measure applied to almost all fields. This is contrary to the principles of integrated pest management and leads to an increased input of insecticides into the environment, by treating a larger number of hectares with a lower amount of active ingredient, and a negative impact on beneficial entomofauna. In addition, studies show that due to the prophylactic approach, the economic and technical justification of this method is often questionable. Extremely important for a quality implementation are the correct processing and implementation of the treatment procedure as well as the selection of appropriate insecticides, which have proven to be problematic in the case of neonicotinoids. The ban on neonicotinoids and the withdrawal of seed treatments in oilseed rape and sugar beet has led to increased problems with a range of pests affecting these crops at an early stage of growth. The results of the present studies indicate good efficacy of active ingredients belonging to the group of anthranilic diamides, cyantraniliprole and chlorantraniliprole in the treatment of maize, soybean, sugar beet and rice seeds on pests of the above-ground part of the plant, but not on wireworms. Good efficacy in controlling wireworms in maize is shown by an insecticide in the naturalites group, spinosad, but it is currently used to treat seeds of vegetable crops, mainly onions, to control onion flies and flies on other vegetable crops. Seed treatment as a method only fits in with the principles of integrated pest management when treated seeds are sown on land where there is a positive prognosis for pest infestation.

Persistence and vertical distribution of neonicotinoids in soils under different citrus orchards chrono sequences from southern China

Continual input of neonicotinoid insecticides occurs in the citrus orchards from southern China. However, it is still unknown about the variations in the distribution and accumulation of neonicotinoids in soil profiles along a long-term chronosequence of cultivation and the driving factors contributing to these shifts. Here, changes of neonicotinoids in the 0–100 cm soil profiles with distinct orchard cultivation age (1, 10, and 20 years) were investigated, and their related factors were further determined. The results showed that the total levels of five target neonicotinoids (∑5NEOs) in the soil profiles were in the range of 0–25.76 ng/g dw. Imidacloprid was the most dominating neonicotinoid, followed by thiamethoxam. We observed higher neonicotinoid accumulations in the soil profiles from the citrus orchards after 10 and 20 years of cultivation. Neonicotinoids migrated deeper into the soil profiles in orchards with a longer time since cultivation. Imidacloprid, thiamethoxam, and the total amount of neonicotinoid (∑5NEOs) were mainly affected by the cultivation age of citrus orchards (accounting for 58.9% variance; P < 0.001); whereas clothianidin, acetamiprid, and thiacloprid were mainly influenced by soil depths (accounting for 66.9–85.2% variance; P < 0.05). Redundancy analyzes further indicated that the enhanced accumulation of neonicotinoids was mainly correlated with the increase of soil organic carbon (SOC) content and soil porosity, and the reduction of bulk density in the profiles of citrus orchards with increasing cultivation age. This study highlights the finding that we should give more concerns about the contamination and ecological risks of neonicotinoids in the orchards with a long cultivation age.

Comparative profitability analysis and resource use efficiency of beekeeping using wooden and poly hive in some selected areas of Bangladesh

Apiarist traditionally adopt wooden hive in beekeeping. Modern poly hive provides a superior environment to raise and keep the honeybee population more vigorous due to its high-tech internal facilities and sanitary system. This study was conducted to examine the comparative profitability and resource use efficiency of beekeeping using traditional wooden hive and modern poly hive in Bangladesh during 2017-18. A total of 60 beekeepers, all have traditional wooden hive and 15 have modern poly hive, were randomly selected from Sirajganj, Gazipur and Satkhira districts to conduct farm level survey with pre-tested questionnaire. Findings of the study reveal that per hive gross and net return were Tk. 11019.26 and 4082.45 for wooden hive and Tk. 27373.34 and 19838.42 for poly hive, respectively. Total cost of beekeeping was Tk. 6936.81 and 7534.92 per hive for wooden and poly hive, respectively. Besides, benefit-cost ratios (BCR) were 1.59 and 3.63 for wooden and poly hive, respectively. Cobb-Douglas production function analysis reveals that labour, transportation, insecticide, equipment, hive and rental costs had significant influence on the returns of beekeeping. More than two times higher BCR and significant positive dummy variable “modern poly hive” indicate the greater profitability of beekeeping in modern poly hives. Resource use efficiency analysis indicates that labour, insecticide, equipment, and honey extraction inputs were under-utilized while feed, transportation, marketing, hive, colony and rental inputs were over-utilized. Beekeeping is also affected by some constraints including high costs of modern poly hive accessories, lack of skilled labour and initial capital, inadequate transportation and marketing facilities. Government and other related organizations should take necessary measures to mitigate those problems. Based on the findings, it is recommended to adopt modern poly hive in beekeeping.&#x0D; Int. J. Agril. Res. Innov. Tech. 11(1): 84-91, June 2021

Phytoene desaturase-silenced citrus as a trap crop with multiple cues to attract Diaphorina citri, the vector of Huanglongbing

Huanglongbing (HLB) is one of the most destructive diseases in citrus worldwide. Unfortunately, HLB has no cure and management relies on insecticides to reduce populations of the vector, Diaphorina citri Kuwayama (Hemiptera: Liviidae). We propose an attract-and-kill strategy using a trap crop as an alternative to vector control to reduce transmission of the pathogen, ‘Candidatus Liberibacter asiaticus’. We evaluated vector response to phytoene desaturase-silenced citrus trees using virus-induced gene silencing technology. Citrus tristeza virus (CTV) was used to produce a phytoene desaturase-silenced citrus (CTV-tPDS) that expresses visual, olfactory, and gustatory cues to attract D. citri. We found that D. citri were more attracted to CTV-tPDS plants with noticeably better fecundity and overall population fitness than on control plants. Moreover, rearing D. citri on CTV-tPDS plants significantly increased their survival probability compared with those reared on control plants. CTV-tPDS plants possessed reduced content of both carotenoid and chlorophyll pigments resulting in a consistent photobleached phenotype on citrus leaves which provided a sufficient close-range visual attractant to stimulate D. citri landing. Additionally, CTV-tPDS plants exhibited an enriched profile of volatile organic compounds (VOCs), which offered adequate olfactory cues to attract psyllid from long-range. Finally, CTV-tPDS plants exhibited an enriched metabolite content of phloem sap and leaves which offered appropriate gustatory cues that influenced probing/feeding behavior. We believe that introducing CTV-tPDS plants (as a trap crop) to D. citri-infested orchards will attract and congregate psyllids to facilitate their removal from the target crop with insecticides or by other means. This new strategy could be deployed relatively quickly and economically to HLB-impacted citrus industries. Moreover, it is an eco-friendly strategy because it should partially reduce the input of chemical insecticides ameliorating the indirect cost of HLB infection.

Effect of hollow‐tine cultivation on crabgrass infestation in cool‐season turf

AbstractHollow‐tine cultivation is a common management practice in cool‐season turfgrass lawns. Research examining the effect of hollow‐tine cultivation on annual crabgrass (Digitaria spp.) infestations in the absence of preemergence herbicides is limited. Multi‐year experiments were conducted on Kentucky bluegrass (Poa pratensis L.) and tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] monostands at the Rutgers University Horticulture Research Farm No. 2 in North Brunswick, NJ to evaluate the effect of hollow‐tine cultivation in early spring, late spring, and autumn on crabgrass infestations. Herbicides to control crabgrass were not applied at any time during the experiments. These monostands were maintained as simulated lawns; mowing, irrigation, fertilizer, fungicide, and insecticide inputs were provided to maintain high turfgrass density. Crabgrass cover was evaluated in late summer each year. In the tall fescue experiment, hollow‐tine cultivation treatments did not affect crabgrass cover. However, in the third year of the tall fescue experiment, a non‐significant trend (P = .08) emerged in which early and late spring cultivation treatments resulted in more crabgrass cover (30 and 35%, respectively) than autumn (24%) and no cultivation (26%). A similar non‐significant trend (P = .056) was observed only during the first year the Kentucky bluegrass experiment as both spring cultivation treatments increased crabgrass cover. This research indicates hollow‐tine cultivation in the springtime does not appreciably increase crabgrass infestations in Kentucky bluegrass or tall fescue in the absence of preemergence herbicides.

Biological control of Halymorpha halys (Stål) (Hemiptera: Pentatomidae) in apple orchards versus corn fields and their adjacent woody habitats: High versus low pesticide-input agroecosystems

Halymorpha halys is an invasive pest in the USA that inflicts damage to specialty crops, and conventional growers have increased use of broad-spectrum insecticides to manage this pest. The impacts of pest management programs on natural enemies of H. halys were examined in high vs. low intensity insecticide input agroecosystems in western North Carolina (USA). Apple orchards and corn fields, with their adjacent wooded habitats, served as the high and low-input environments, respectively. Sentinel egg masses and yellow sticky cards were deployed in these agroecosystems to compare predation and parasitism on H. halys eggs, and presence, abundance, and richness of natural enemies. A total of approximately 85% of all sentinel eggs deployed in apple orchards in both 2018 and 2019 produced a healthy stink bug nymph, higher than all other habitats. A total of 26.6% and 32.9% of eggs deployed in wooded habitats bordering corn exhibited mortality due to natural enemy attack in 2018 and 2019, respectively. Comparatively, eggs deployed in apple borders had 10.0% and 17.8% of total eggs killed by natural enemies, in 2018 and 2019, respectively. Corn agroecosystems generally had greater predation and parasitism of sentinel eggs, and greater richness and abundance of predators detected on yellow sticky cards compared to apple agroecosystems. Wooded habitats bordering crops serve as population reservoirs for H. halys, allowing for egg laying and dispersal into crops. If these areas are protected as refuge areas free from insecticide drift, such as from apple orchards, they can also harbor thriving natural enemy populations that could reduce populations of H. halys. Wooded areas free from harsh broad-spectrum insecticides are an important component for successful conservation and augmentative biological control in neighboring crops.

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.

A comparison of repetitive releases of single or multiple natural enemy species on the suppression of Bemisia tabaci infesting poinsettias

The repetitive release of Eretmocerus eremicus (Mercet) (Hymenoptera: Aphelinidae) to manage Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a promising strategy on poinsettias in protected culture. Management of B. tabaci, however, may be improved if releases include multiple natural enemy species that attack different B. tabaci life stages. In this study, we investigate whether suppression of B. tabaci on poinsettias is improved by the combination of E. eremicus and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) compared to either natural enemy alone at release rates 1.2 – 2.7-fold the cost of conventional insecticide inputs. We found that all natural enemy treatments provided significant suppression when starting whitefly populations were below 13.7 ± 1.7 immatures per plant. The combination of E. eremicus and A. swirskii performed equally well compared to either natural enemy alone, in both a substitutive and additive design. These effects, however, were density dependent; neither natural enemy alone nor the combination of natural enemies suppressed whiteflies if initial whitefly density was above 40.8 ± 2.5 immature whiteflies per plant.

Toward the Integration of an Attract-and-Kill Approach with Entomopathogenic Nematodes to Control Multiple Life Stages of Plum Curculio (Coleoptera: Curculionidae).

Efforts to reduce insecticide inputs against plum curculio, Conotrachelus nenuphar, a key pest of apples in eastern North America, include perimeter-row insecticide sprays applied after the whole-orchard petal fall spray to manage dispersing adults and, more recently, insecticide sprays confined to odor-baited trap trees. Entomopathogenic nematodes (EPNs) are virulent to ground-dwelling stages of C. nenuphar, and may be applied to the ground underneath trap-tree canopies. Here, we (1) compared the efficacy of the odor-baited trap tree approach with grower-prescribed (=grower standard) sprays to manage C. nenuphar populations over a six-year period in seven commercial apple orchards in New England; and (2) assessed the performance of the EPN Steinernema riobrave at suppressing ground-dwelling stages of C. nenuphar. In addition, the performance of S. riobrave was compared against that of S. carpocapsae and S. feltiae in one year. Across the six years, percent fruit injury on trap tree plots averaged 11.3% on odor-baited trap trees and 1.4% on unbaited trees in grower standard plots, highlighting the ability of trap trees to aggregate C. nenuphar activity and subsequent injury. Mean percentage injury on fruit sampled from interior trees, the strongest measure of treatment performance, in trap tree plots did not differ significantly from that recorded on interior trees in grower standard spray plots (0.95 vs. 0.68%, respectively). Steinernema riobrave consistently reduced C. nenuphar populations as indicated by the significantly lower number of adult C. nenuphar that emerged from the soil, when compared to water control. Steinernema carpocapsae and S. riobrave performed similarly well, and both EPN species outperformed S. feltiae. Our combined findings indicate that an IPM approach that targets multiple life stages of C. nenuphar has the potential to manage this pest more sustainably in a reduced-spray environment.

Evaluation of Biorational Insecticides as Stand-alone Treatments for the Management of the Pigweed Flea Beetle, Disonycha glabrata (Coleoptera: Chrysomelidae), in Organic Production of Amaranthus spp.

The pigweed flea beetle, Disonycha glabrata, is the most damaging insect pest on Amaranthus spp. in the Piedmont zone of North Carolina (NC), United States. It is capable of causing severe yield loss on amaranth greens if uncontrolled. Field experiments were conducted over two growing seasons (Summer 2017 and 2018) in Greensboro, NC, to evaluate OMRI-approved biorational insecticides against D. glabrata in organic amaranth production. Insecticides evaluated included Azatin&amp;reg; O (azadiractin), Ecotec&amp;reg; (oils: rosemary, peppermint and geraniol), Entrust&amp;reg; (spinosad) and PyGanic&amp;reg; (pyrethrins) as stand-alone threshold-driven treatments applied at recommended label rates. Insecticide treatment action threshold (AT) was 2 (on a scale of 5) representing 20-40% leaf damage. The efficacy of the insecticides against D. glabrata population differed significantly within the amaranth varieties in comparison to their respective controls: treatments with Entrust&amp;reg; and PyGanic&amp;reg; on Green Callaloo and Red Leaf recorded 80% reduction in beetle population while Ecotec&amp;reg; gave only a 15% beetle reduction. The Azatin&amp;reg; O treatments recorded the highest D. glabrata population, sometimes greater than the control. Marketable fresh leaf yield from both Green Callaloo and Red Leaf amaranth was highest in the Entrust&amp;reg; and PyGanic&amp;reg; treatments. Hopi Red-Dye and Molten Fire amaranths showed some resistance to beetle damage; they are also intrinsically low yielding. These findings provide information that would make organic amaranth production possible with only limited and safe insecticide input using OMRI-approved insecticides in a threshold-driven manner, an important step towards the sustainable management of D. glabrata and amaranth production.

Comparison and Refinement of Integrated Pest Management Tactics for Halyomorpha halys (Hemiptera: Pentatomidae) Management in Apple Orchards.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) has been managed primarily with broad-spectrum insecticides in orchard systems. Recently, IPM techniques have been developed specifically for managing H. halys in apple orchards to reduce insecticide inputs and take advantage of its perimeter-driven behavior. In 2015 and 2016, we compared these IPM tactics to one another and an untreated control to measure differences in overall crop protection and insecticide inputs. Tactics included trap-based threshold-triggered spray applications, perimeter-based attract-and-kill (AK) trees treated every 7- and 14-d, and perimeter spray applications applied every 7- and 14-d. All plots were monitored with baited black pyramid traps deployed in plot interiors. In both years, mean number of H. halys captured in untreated control plot traps was significantly greater than plots managed using IPM tactics. In 2015, significantly more insecticide applications were made in 7- and 14-d perimeter and AK plots compared with trap-based threshold plots. There was no significant difference in the percentage of injured fruit in plot interiors among IPM tactics; all were significantly lower than the control. In 2016, significantly more insecticide applications were made in 7-d perimeter spray and AK plots compared with all other treatments. Significantly less injury was detected in plot interiors for 7- and 14-d perimeter and trap-based threshold plots compared with the control and 7- and 14-d AK plots. Although all IPM tactics reduced H. halys injury in apples using a trap-based treatment threshold required fewer insecticide inputs and only during brief periods of the season, while all others required season-long maintenance.

Landscape and climatic effects driving spatiotemporal abundance of Lygus lineolaris (Hemiptera: Miridae) in cotton agroecosystems

Lygus lineolaris populations have become increasingly problematic in Virginia cotton since 2013. Although production practices have changed, changes in landscape composition and climatic conditions are also anecdotally associated with increasing populations. To better understand the recent increase in L. lineolaris infestations in Virginia cotton, 56 commercial cotton fields were sampled weekly in 2017 and 2018 for a nine-week period during the growing season. Insect density was measured using sweep net and black drop cloth sampling, targeting adult and nymphal populations, respectively. Geospatial crop production and forest disturbance data were used to measure the composition and management history of landscapes adjacent to sample fields. We also used spatial climate data sets to document the relationship between increasing L. lineolaris and temperature variation. We investigated the significance of landscape composition and climatic effects increasing L. lineolaris infestation intensity using a regression modeling approach. We found the best overall predictor of L. lineolaris abundance was higher annual minimum temperatures. Several crop components in the landscape were significant, specifically corn and double-crop winter wheat and soybeans, but these habitat patches did not explain high levels of variability. Results of this study suggest that increasing minimum temperatures will favor L. lineolaris and may translate into elevated infestation intensity and increasing dependence on insecticide inputs to manage this problematic pest of cotton. Results of this study will be important to describe short- and long-term factors driving L. lineolaris infestation risk in cotton agroecosystems.

Comparing Prophylactic Versus Threshold-Based Insecticide Programs for Striped Cucumber Beetle (Coleoptera: Chrysomelidae) Management in Watermelon.

In cucurbit crops such as watermelon, implementation of integrated pest management (IPM) is important due to the high reliance on bees for fruit set, along with mounting evidence of the risks of insecticide use associated with pollinator health. Yet, IPM adoption, on-farm pesticide use behaviors, their costs, and impacts on the primary insect pest (striped cucumber beetle, Acalymma vittatum F.) are poorly known in one of the key watermelon-growing regions, the Midwestern United States. To better understand how to implement IPM into watermelon production, we assessed pest management practices on commercial watermelon farms using 30 field sites in Indiana and Illinois over 2 yr in 2017 and 2018. Across all sampling dates, beetles never crossed the economic threshold of five beetles/plant at any farm and most were maintained at densities far below this level (i.e., <1 beetle/plant). Moreover, we documented a wide range of insecticide inputs (mean ca. 5 applications per field per season; max. 10 applications) that were largely dominated by inexpensive foliar pyrethroid sprays; however, insecticide application frequency was poorly correlated with pest counts, suggesting that most of these applications were unnecessary. We calculated that the cost of the average insecticide program far exceeds the cost of scouting, and thus IPM is estimated to save growers ca. $1,000 per field under average conditions (i.e., field size, insecticide cost). These data strongly indicate that current management practices on commercial farms in the Midwest would benefit from implementing more threshold-based IPM programs with potential increases in both farm profitability and pollination services.

Cover crops improve early season natural enemy recruitment and pest management in cotton production

A shift to more ecologically based farming practices could improve the sustainability and economic stability of agricultural systems. Habitat management in and around agricultural fields can provide stable environments that aid in the proliferation of natural enemy communities that moderate pest populations and injury. Winter cover crops offer a potentially cost-effective approach to improving habitat that supports natural enemy communities early in the growing season. We investigated the effects of winter cover crops including cereal rye (Secale cereal L.) and crimson clover (Trifolium incarnatum L.) on the abundance and diversity of natural enemies, key pest populations, biological control services, and cotton yield. Winter cover crops were established on 0.4 ha replicated field plots in the fall of 2017 and 2018. Suction sampling during each cotton development stage demonstrated that a rye cover crop promoted greater abundance and diversity of natural enemy communities in early cotton stages. Extensive leaf sampling of seedling cotton showed that cover crops significantly reduced thrips infestations. Furthermore, stink bug boll injury decreased on plots prepared with a rye cover compared to cotton lacking this additional habitat. Combining end of season yield results and management practices with an economic analysis of the costs of production, the value of cotton grown into a cover crop was cost competitive with conventional (no cover) cotton production. These results suggest that conventional growers utilizing cover crops could reduce insecticide inputs through natural reductions in pest pressure, and overall do not incur additional production costs.

Nutrients and sediment modify the impacts of a neonicotinoid insecticide on freshwater community structure and ecosystemfunctioning.

Pesticides are important contributors to the global freshwater biodiversity crisis. Among pesticides, neonicotinoids are the best-selling class of agricultural insecticides and are suspected to represent significant risks to freshwater and terrestrial ecosystems worldwide. Despite growing recognition that neonicotinoid impacts may be modified by the presence of additional stressors, there is limited information about their interactions with other agricultural stressors in freshwater ecosystems. We conducted an outdoor pond-mesocosm experiment to investigate the individual and interactive effects of nutrients, fine sediment, and imidacloprid (a neonicotinoid insecticide) inputs on freshwater community structure (density, diversity, and composition of zooplankton and benthic invertebrates) and ecosystem functioning (ecosystem metabolism, primary production, and organic matter decomposition). We hypothesized antagonistic nutrient-imidacloprid, and synergistic sediment-imidacloprid interactions, affecting aquatic invertebrate communities. The three stressors had significant individual and interactive effects on pond ecosystems. The insecticide neutralized the positive effects of nutrient additions on benthic invertebrate richness and mitigated the negative effects of sediment on zooplankton communities (antagonistic interactions). Moreover, we observed compensatory responses of tolerant benthic invertebrates, which resulted in reversal interactions between sediment and imidacloprid. Furthermore, our observations suggest that imidacloprid has the potential to increase net ecosystem production at environmentally relevant concentrations. Our findings support the hypothesis that the impacts of imidacloprid may be modified by other agricultural stressors. This has important implications on a global scale, given the widespread use of these pesticides in intensive agricultural landscapes and the growing body of literature suggesting that traditional pesticide assessment frameworks, based on laboratory toxicity tests alone, may be insufficient to adequately predict effects to complex freshwater ecosystems.