Insecticide Programs Research Articles

A Novel Interaction of Nesidiocoris tenuis (Hemiptera: Miridae) as a Biological Control Agent of Bactericera cockerelli (Hemiptera: Triozidae) in Potato.

Nesidiocoris tenuis (Hemiptera: Miridae) is a generalist predator commonly used to control the whitefly Bemisia tabaci in Europe. This mirid has been found and established in South Texas, where it was initially observed feeding on nymphs of the psyllid Bactericera cockerelli (Hemiptera: Triozidae) in open tomato fields. B. cockerelli is the vector of the fastidious bacterium "Candidatus Liberibacter solanacearum" that causes diseases in several solanaceous crops, including zebra chip (ZC) disease in potatoes. There is a need to better understand how this predator impacts the control of important crop pests, such as potato psyllids. We assessed the interactions between N. tenuis and B. cockerelli in three different environmental settings. First, we estimated the numeric response of N. tenuis preying on B. cockerelli under laboratory and greenhouse conditions. Second, we evaluated the predator-prey interaction under controlled field cage conditions. Then, we exposed N. tenuis under controlled field release conditions to the natural occurrence of B. cockerelli. Finally, we assessed the compatibility between the use of N. tenuis as a biological control agent in a field study and its impact on ZC disease incidence, severity in potato tubers, and potato yield. Laboratory and greenhouse experiments resulted in diverse types of functional model responses, including exponential and linear mathematical models. Our findings revealed a significant predation effect exerted by N. tenuis, resulting in a reduction of more than fourfold in the number of B. cockerelli nymphs per cage. Specifically, the nymphal population decreased from 21 ± 3.2 in the absence of N. tenuis to 5 ± 1.6 when N. tenuis was present. Furthermore, the combination of N. tenuis with a reduced insecticide program increased potato yields, but only reduced ZC tuber incidence in one of two potato cultivars evaluated, and in one season. Findings from these studies indicate that N. tenuis could be effective as a biological control agent for B. cockerelli in potato production in South Texas. This is the first report of N. tenuis preying on immature stages of any psyllid species.

Evaluation of Torac in full-season insecticide programs for thrips control in onion in Wisconsin, 2023

Evaluation of Torac in full-season insecticide programs for thrips control in onion in Wisconsin, 2023

Managing insect and plant pathogen pests with organic and conventional pesticides in onions.

Onion thrips (Thrips tabaci Lindeman, Thysanoptera: Thripidae) is a significant insect pest of onions (Allium cepa L., Asparagales: Amaryllidaceae). In addition to feeding on onion foliage, they may spread plant pathogens. Currently, onion thrips and pathogens are managed as separate pests with insecticides and fungicides. It may be beneficial to manage these pests simultaneously as limiting onion thrips may reduce pathogen damage. We tested combinations of bio- and conventional pesticides in a season-long management program in Michigan onion fields. From 2020 to 2022, we counted onion thrips weekly and visually estimated plant foliage necrotic damage (%) in experimental plots each year. In 2020, we tested 6 treatment programs including: azadirachtin, spinosad, a copper-based fungicide, azadirachtin + copper-based fungicide, spinosad + copper-based fungicide, and untreated control. The thrips populations were not significantly reduced compared to the control, but necrotic damage was reduced significantly in spinosad-treated plots. In 2021, we tested a combination of 8 bio- and conventional pesticide programs. Compared to the control, the bioinsecticides did not reduce onion thrips populations, but the conventional pesticide programs reduced both onion thrips numbers and necrotic damage. In 2022, we tested only conventional insecticide programs but included 3 different action thresholds for initiation and applied them with or without a fungicide, for 8 treatments. All insecticide programs reduced onion thrips compared to the control, the action threshold did not impact thrips numbers significantly. Overall, the use of action thresholds can lead to fewer insecticide applications and a lower incidence of leaf damage.

Profiling lipidomic changes in dengue-resistant and dengue-susceptible strains of Colombian Aedes aegypti after dengue virus challenge.

The mosquito Aedes aegypti is the primary vector for all four serotypes of dengue viruses (DENV1-4), which infect millions across the globe each year. Traditional insecticide programs have been transiently effective at minimizing cases; however, insecticide resistance and habitat expansion have caused cases of DENV to surge over the last decade. There is an urgent need to develop novel vector control measures, but these are contingent on a detailed understanding of host-parasite interactions. Here, we have utilized lipidomics to survey the profiles of naturally DENV-resistant (Cali-MIB) or susceptible (Cali-S) populations of Ae. aegypti, isolated from Cali, Colombia, when fed on blood meals containing DENV. Control insects were fed on a DENV-free blood meal. Midguts were dissected from Cali-MIB and Cali-S females at three time points post-infectious blood meal, 18, 24 and 36h, to identify changes in the lipidome at key times associated with the entry, replication and exit of DENV from midgut cells. We used principal component analysis to visualize broad patterns in lipidomic profiles between the treatment groups, and significance analysis of microarray to determine lipids that were altered in response to viral challenge. These data can be used to identify molecules or metabolic pathways particular to the susceptible or refractory phenotypes, and possibly lead to the generation of stable, DENV-resistant strains of Ae. aegypti.

Evaluating Options to Increase the Efficacy of Biocontrol Agents for the Management of Pantoea spp. Under Field Conditions.

Center rot of onion is caused by a complex of plant pathogenic Pantoea species, which can lead to significant yield losses in the field and during storage. Conventional growers use foliar protectants such as a mixture of copper bactericides and an ethylene-bis-dithiocarbamate (EBDC) fungicide to manage the disease; however, organic growers have limited management options besides copper-protectants. Biocontrol agents (BCAs) provide an alternative; however, their efficacy could be compromised due in part to their inability to colonize the foliage. We hypothesized that pretreatment with peroxide (OxiDate 2.0: a.i., hydrogen peroxide and peroxyacetic acid) enhances the colonizing ability of the subsequently applied BCAs, leading to effective center rot management. Field trials were conducted in 2020 and 2021 to assess the efficacy of peroxide, BCAs (Serenade ASO: Bacillus subtilis and BlightBan: Pseudomonas fluorescens), and an insecticide program (tank mix of spinosad and neem oil) to manage center rot. We observed no significant difference in foliar area under the disease progress curve (AUDPC) between the peroxide pretreated P. fluorescens plots and only P. fluorescens-treated plots in 2020 and 2021. Peroxide pretreatment before B. subtilis application significantly reduced the foliar AUDPC as compared with the stand-alone B. subtilis treatment in 2020; however, no such difference was observed in 2021. Similarly, peroxide pretreatment before either of the BCAs did not seem to reduce the incidence of bulb rot as compared with the stand-alone BCA treatment in any of the trials (2020 and 2021). Additionally, our foliar microbiome study showed comparatively higher P. fluorescens retention on peroxide pretreated onion foliage; however, at the end of the growing season, P. fluorescens was drastically reduced and was virtually nonexistent (<0.002% of the total reads). Overall, the pretreatment with peroxide had a limited effect in improving the foliar colonizing ability of BCAs and consequently a limited effect in managing center rot.

Study the Application of Insecticide Program and its Impact on the Relationship between Leaf Miner Liriomyza huidobrensis Populations and the Early Blight Disease in Potato Fields

Study the Application of Insecticide Program and its Impact on the Relationship between Leaf Miner Liriomyza huidobrensis Populations and the Early Blight Disease in Potato Fields

Does IPPM bear fruit? Evaluating reduced‐risk insecticide programmes on pests, pollinators and marketable yield

Abstract Integrated pest and pollinator management (IPPM) has been touted as a novel approach to control pests while mitigating negative effects of insecticides on pollinators. In addition to non‐chemical approaches, IPPM programmes focus on insecticide treatments with low bee toxicity, threshold‐based applications and restricted timings to avoid sprays during pollinator foraging. However, the singular and combined effect of this approach on pollination services and pest management is understudied and generally lacks field validation. In two field studies, we evaluated the effect of IPPM insecticide programmes on striped cucumber beetle (Acalymma vittatum) management, pollination and watermelon yield. The first trial (2020) featured insecticide treatments representing a factorial combination of (1) products varying in bee toxicity (bifenthrin, cyclaniliprole and acetamiprid), (2) application frequencies (weekly vs. threshold‐based) and (3) application timings (AM vs. PM), as well as an untreated control. These data were then used to inform a second trial (2021) that applied two insecticide treatments (IPPM based or grower standard) to commercial‐scale (20–30 acres) fields in collaboration with regional watermelon farms. Weekly beetle densities, pollinator visitation and yield data were collected to determine programme efficacy. Overall, beetle infestations were successfully managed with all insecticide treatments, none of which compromised marketable yield. In 2020, threshold‐based insecticide programmes offered statistically similar levels of pest control but required 20%–80% fewer applications compared to a weekly programme. Furthermore, pollinator visitation was increased in threshold‐based programmes by ~42% across all products. The on‐farm validation trial in 2021 upheld these findings; IPPM fields had effective beetle control but with 1–7 fewer insecticide applications compared to grower standard fields. IPPM fields also had 62% greater pollinator visitation and 49% more melons during harvest compared to grower standard fields. Synthesis and applications. Our study demonstrates the capacity of IPPM programmes to manage pests while mitigating negative effects on pollinators. In particular, administering insecticide applications by pest thresholds led to the greatest enhancement in pollinator function. These findings also suggest that growers can benefit from this approach with reduced insecticide costs while encouraging pollination in pollinator‐dependent crops.

Development and validation of a larval bioassay and selection protocol for insecticide resistance in Drosophila suzukii.

The rapid invasion of Drosophila suzukii (Matsumura) throughout Europe and the Americas has led to an increased reliance on calendar-based broad-spectrum insecticide programs among berry and cherry growers. Relatively few active ingredients (AIs) are currently available for effective D. suzukii management, and studies from multiple growing regions indicate that susceptibility to at least some of these materials is declining. Greater effort is needed to understand the status of susceptibility across field populations and the potential for increased resistance to develop, as well as the possible fitness costs incurred by resistant individuals. However, current bioassay protocols used for resistance monitoring and selection studies (i.e. resistance risk assessments) are labor-intensive and costly, making large-scale studies difficult to conduct. Here, we first present a novel bioassay protocol using larvae that requires little effort or cost to implement beyond what is needed for basic D. suzukii laboratory colony maintenance. We then perform dose-response bioassays using this protocol to identify larval lethal concentrations for three commonly used insecticides (malathion, spinosad and zeta-cypermethrin) in a susceptible population. Finally, resistance risk assessments were conducted using a population of D. suzukii from commercial caneberry fields near Watsonville, CA. We find that five generations of larval selection with a discriminating dose is sufficient to significantly increase both larval (malathion and spinosad) and adult (spinosad) resistance to the target AIs. This approach provides a simple, cost-effective tool for assaying susceptibility of D. suzukii populations to insecticides and for selecting resistant insect lines for resistance management research.

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.

Developing a mealybug pheromone monitoring tool to enhance IPM practices in New Zealand vineyards

Mealybugs are phloem-feeding insects found on many crops worldwide. In New Zealand vineyards, they transmit the economically important Grapevine leafroll-associated virus 3 (GLRaV-3). For some mealybug species, synthetic sex pheromones have been commercialised, and are used as monitoring tools. The mealybugs Pseudococcus longispinus and Pseudococcus calceolariae are major pests in many New Zealand vineyards. We present work on the development of a combined P. longispinus and P. calceolariae pheromone lure. The optimal dose for monitoring P. longispinus was found to be 10 µg of the (S)-(+)-enantiomer, either alone or in the racemic mixture. Addition of the corresponding alcohol did not improve trap catch of P. longispinus. Both the P. longispinus and the P. calceolariae pheromone lures remained active in the field for 90 days. Combining the 2 species’ pheromones had no negative effects on male mealybug trap catch for either species. We conclude that the pheromone ester alone is the best lure for the male P. longispinus. Combining the two mealybug species’ pheromones into a single lure provides the New Zealand viticultural industry with an efficient monitoring tool. Late-vintage deployment of baited lures will provide information on mealybug abundance and local distribution that will inform the scope of future insecticide programmes, to target areas based on need rather than an area-wide application by default.

Impact of insecticide programs on pests, the predatory mite Phytoseiulus persimilis, and staked tomato profitability.

Various insecticides are available to manage diverse pest complexes in commercial vegetable production, but knowledge gaps exist regarding their overall performance in pest suppression, profitability, and compatibility with biological control. We conducted trials in staked tomatoes in western North Carolina in 2017-2018 to compare how different insecticide programs managed key pests and their interactions with Phytoseiulus persimilis Athias-Henriot, a predator of the twospotted spider mite (TSSM, Tetranychus urticae Koch). Treatments compared no insecticides to broad-spectrum ('hard') foliar applications, selective ('soft') foliar applications, and to chemigation of selective systemic insecticides. Treatment efficacy was based on pest control, net profitability, and Environmental Impact Quotient (EIQ) ratings comparing environmental and human health risks. All programs similarly suppressed aphids, while flower thrips and flea beetle populations were low and unaffected by program. Only the 'hard' foliar program suppressed TSSM (including P. persimilis), which quickly rebounded. This program inhibited biological control, and eventual TSSM suppression was likely caused by P. persimilis immigrating from nearby plots. All programs were generally equivalent in reducing fruit damage. Net profits were similar among insecticide programs, which were significantly greater than in untreated plots. Yield and profit trends were similar both years, but impacted by record flooding in 2018. Safer and more selective chemigation and 'soft' foliar programs were as effective and economical as the 'hard' foliar program, while also conserving biological control. These results support existing research demonstrating that improved insecticide use can be integrated with biological control for more profitable and environmentally sustainable vegetable production. © 2022 Society of Chemical Industry.

Annual bluegrass weevil (Listronotus maculicollis) and paclobutrazol control annual bluegrass (Poa annua) in creeping bentgrass fairways

AbstractThe annual bluegrass weevil (ABW) is a pest of fine turfgrass, but recent research has found that withholding insecticides for ABW control can reduce annual bluegrass cover. The objective of this research was to evaluate threshold-based insecticide and paclobutrazol programs for annual bluegrass control. The effect of three insecticide programs (preventive, threshold, and no insecticide) and four rates of paclobutrazol (0, 70, 105, or 210 g ha−1 applied monthly) were evaluated. Replicate experiments were conducted from April to November in both 2018 and 2019 on a mixed creeping bentgrass and annual bluegrass fairway in North Brunswick, NJ. By the conclusion of both experiments, all paclobutrazol programs exhibited reduced annual bluegrass cover compared with the nontreated plots. In threshold and no-insecticide programs, reduction in annual bluegrass cover was enhanced by paclobutrazol applied at 105 g ha−1 in both years, and at 70 g ha−1 in the 2019 experiment. Paclobutrazol at 210 g ha−1 resulted in annual bluegrass cover of &lt;20% regardless of insecticide program. In 2019, threshold-based ABW control without paclobutrazol provided similar annual bluegrass control as monthly applications of paclobutrazol at 70 and 105 g ha−1 with the preventive insecticide program. A reduction in turfgrass quality from threshold-based insecticide programs persisted for a shorter duration than the no-insecticide program, regardless of paclobutrazol treatment. Threshold-based ABW insecticide programs that allow ABW feeding damage to occur can result in reduced annual bluegrass cover. These reductions were further enhanced by paclobutrazol applications. The combination of threshold-level insecticide with moderate rates of paclobutrazol (70 to 105 g ha−1) provided reductions in annual bluegrass cover that were similar to the highest rate of paclobutrazol (210 g ha−1) without ABW damage. Turfgrass managers who integrate the threshold-level insecticide approach and monthly paclobutrazol applications may achieve greater annual bluegrass control than either strategy alone if temporary reductions in turf quality can be tolerated.

Pheromone Deployment Strategies for Mating Disruption of a Vineyard Mealybug.

The mealybug, Planococcus ficus (Signoret), is a primary vineyard pest in California and other grape-growing regions throughout the World. Mating disruption programs are commercially available to manage Pl. ficus, but widespread adoption has been limited, in part, by high costs compared with insecticide programs. To improve mating disruption economic effectiveness, different deployment technologies (passive, aerosol, and microencapsulated formulations) were individually examined. Adult male Pl. ficus captures in pheromone traps and categorical ratings of vine infestation or crop damage suggest that all deployment strategies lowered mealybug densities or damage. Using passive dispensers, deployment rates of 310 and 465 per ha lowered Pl. ficus crop damage similar to 615 per ha, a rate commonly used in commercial operations; reduced rates would lower product and deployment costs. Meso dispensers, containing more a.i., deployed at 35 per ha did not have a treatment impact, but a microencapsulated formulation and aerosol canisters lowered male flight captures and/or crop damage. Male mealybug flight activity was greatest from 0500–1100 hr, which coincided with temperatures >16° and <32°C. These restricted times and temperatures suggest programable dispensers might allow pheromone deployment to coincide only with flight patterns. A large field trial using passive dispensers found greater treatment separation after 3 yr of pheromone deployment. Discrepancies in results among vineyards may be related to Pl. ficus density, but combined results from all trials suggest that different deployment technologies can be used to impact Pl. ficus densities and damage, even at reduced rates, especially with continued use over multiple seasons.

Developing female removal for Cydia pomonella (Lepidoptera: Tortricidae) in organic pear in the USA and Italy

AbstractSeventeen trials were conducted using traps baited with kairomone‐based lures to evaluate female removal (FR) as an effective management tactic for codling moth, Cydia pomonella, L., in organic pear, Pyrus communis L., production in Italy and USA during 2019–2020. Studies included paired plots (0.4–1.4 ha) treated with or without 60 traps ha−1 in cultivars Bartlett and Abate Fétel. Paired plots were also treated together with or without mating disruption (MD) and with similar spray programmes. Three‐, four‐, and five‐component lures were used with several trap types: green, clear or green/white bucket traps and orange delta traps. The three‐component lure consisted of (E,E)‐8,10‐dodecadien‐1‐ol (sex pheromone, PH), (E,Z)‐2,4‐ethyl decadienoate (pear ester, PE) and acetic acid (AA); the four‐component lure was PE, (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT), 6‐ethenyl‐2,2,6‐trimethyloxan‐3‐ol (pyranoid linalool oxide, LOX), and AA, and the five‐component lure had PH added. Preliminary studies were also conducted to evaluate the trapping efficacy of non‐saturating bucket traps. A clear bucket trap baited with PE/DMNT/LOX + AA captured 97‐fold more codling moth females than an orange delta trap baited with PH/PE. However, female captures did not differ between traps when both were baited with the four‐component lure. Fruit injury from codling moth was significantly reduced with the implementation of FR in both pear production regions. At harvest, mean fruit protection in the USA studies was 65% and 27% in Italy. This difference was likely associated with the four‐component lure being less effective in Italy than in the USA. Nevertheless, results demonstrate that FR can be a useful approach to remove females immigrating into orchards and as a new tactic to reduce pest pressure in selected areas of orchards allowing both MD and organic insecticide programmes to be more effective. Further studies should investigate the cost‐benefit of matching the intensity of FR to variable pest pressures.

Resampling of wild bees across fifteen years reveals variable species declines and recoveries after extreme weather

Despite concerns about the status of wild bees, there have been few studies with repeated sampling of these insects at the same locations using the same method. There is an urgent need for longitudinal studies to understand species- and population-level dynamics and the drivers of change, especially in pollinator-dependent crop systems. We sampled wild bees in highbush blueberry fields in three multi-year sampling periods between 2004 and 2018 to determine changes in the wild bee community active during bloom. We captured 35% (162 species) of the known Michigan bee fauna across the three sampling periods. Andrena, Lasioglossum and Ceratina were the dominant genera, though species composition varied significantly between sampling periods. Wild bee abundance (measured as captures in the pan traps) declined 61% and richness declined 33% between the first (2004–2006) and second (2013–2014) sampling periods. This was followed by limited recovery in species abundance and richness in the third sampling period (2017–2018). Some species showed dramatic abundance declines, particularly the blueberry specialist Andrena carolina. By contrast, other species showed stable or increasing prevalence, and population trajectories were not correlated with life history traits. Potential causes of the observed decline include increased use of insecticides and extreme spring weather in 2012. While farms varied in pest management intensity and overall insecticide program risk increased over time, there was no correlation between bee declines and insecticide use. Insecticide program risk increased between the second and third sampling periods, while most species increased in abundance. We therefore conclude the observed declines were most likely caused by extreme spring weather in 2012 resulting in widespread damage to flowering plants that provide resources for bees. Long-term monitoring to identifying species more vulnerable to environmental perturbations can help guide conservation recommendations as extreme weather events become more common.

Annual bluegrass weevil, paclobutrazol, and overseeding for annual bluegrass control in cool‐season turfgrass

AbstractThe annual bluegrass weevil (ABW; Listronotus maculicollis Kirby) host preference for annual bluegrass (Poa annua L.) is well documented, but ABW efficacy for annual bluegrass control in mixed turfgrass stands has not been researched. This study evaluated threshold‐based insecticide ABW control for annual bluegrass control in mixed‐species golf course fairway turfgrass. To investigate integrated pest management programs for annual bluegrass control in fairways, the effects of creeping bentgrass (Agrostis stolonifera L.) overseeding, three insecticide programs (preventative, threshold‐based, and no insecticide), and the plant growth regulator paclobutrazol (280 g ha–1, applied monthly) were evaluated for annual bluegrass control in field experiments conducted over 2 yr on golf fairways in North Brunswick and Bloomfield, NJ. Treatments were replicated four times and arranged in a split‐split‐plot randomized block design. Overseeding (whole‐plot factor) did not affect annual bluegrass cover at either location. Paclobutrazol (split‐plot factor) reduced annual bluegrass cover each year at both locations. At the North Brunswick site, paclobutrazol resulted in 0% annual bluegrass cover, compared with 37% in the nontreated control at the conclusion of the 2‐yr experiment. Insecticide program (split‐split‐plot factor) only affected annual bluegrass cover at the North Brunswick site. In the absence of paclobutrazol, the no insecticide program had lower annual bluegrass cover (23%) than the threshold (37%) and preventative (44%) programs at the conclusion of the experiment. These findings show that monthly paclobutrazol applications during the growing season can reduce or eliminate annual bluegrass after 2 yr. This is the first study to show that omitting ABW insecticidal control can also reduce annual bluegrass, although efficacy was site specific.

Organic and Conventional Insecticide Programs for Control of Pear Psylla in Pear, 2020

Organic and Conventional Insecticide Programs for Control of Pear Psylla in Pear, 2020

Composting susceptible fruit wastes reduces Drosophila suzukii (Diptera: Drosophilidae) reproductive habitat.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive, polyphagous vinegar fly pest that is primarily controlled by calendar-based broad-spectrum insecticide programs. Nonchemical management tactics are urgently needed to reestablish IPM within affected berry and cherry cropping systems. Composting is a post-harvest crop sanitation strategy that could potentially be used to manage D. suzukii infestation of fruit wastes. This study found that D. suzukii emergence decreased exponentially with an increasing proportion of chicken manure, with emergence reduced by 95% in compost treatments containing 25% chicken manure. Furthermore, Drosophila melanogaster (Meigen) (Diptera: Drosophilidae) demonstrated a response similar to D. suzukii in the field. Integrating this control tactic into existing D. suzukii management programs may help to reduce the need for insecticide applications for D. suzukii as well as provide improved management of other Drosophila spp. in post-harvest systems.

Biopesticides for Management of Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) and Tomato Yellow Leaf Curl Virus.

The sweetpotato whitefly, Bemisia tabaci MEAM1 Gennadius, is a global pest of tomato, transmitting Tomato yellow leaf curl virus (TYLCV). Management of B. tabaci is challenging in part because of its ability to develop resistance to insecticides. Biopesticides include materials that control B. tabaci via mechanisms that do not select for resistance. Field experiments were conducted in the spring and fall of 2016 and 2017 at the University of Florida's Gulf Coast Research and Education Center in west central Florida to compare biopesticides to conventional insecticides for management of B. tabaci and TYLCV. Insecticide rotations were designed in part around the concept that conventional insecticide programs should group modes of action according to 5-wk treatment intervals, corresponding to an estimated 5-wk generation time for the pest. In 2016, when tomato was treated during the first 5-wk treatment interval with either biopesticides or neonicotinoid insecticides, insecticidal soap contributed to a reduction in whitefly egg numbers and percentage TYLCV that was comparable to results achieved with dinotefuran. In contrast, egg numbers and virus incidence in plants treated with kaolin clay tended to be numerically higher than the untreated control. In spring 2017, comparisons of biopesticides and conventional ovicides/nymphicides during the second 5-wk treatment interval showed that biopesticides can provide comparable reduction in nymph numbers to conventional insecticides. While data from these trials confirm that biopesticides can reduce numbers of whitefly eggs and nymphs, they indicate that season-long programs of the biopesticides evaluated may not reduce transmission of TYLCV below economically acceptable levels.

Challenges in integrated pest management: A case study of onion thrips and bacterial bulb rot in onion

Most agricultural production systems face challenges with multiple arthropods, plant pathogens and/or weed species, but few studies address the impact of multiple pests when developing integrated pest management programs. In onion production, onion thrips and bacterial bulb rot are primary constraints, and choice of onion cultivar, fertility regime and insecticide use may be important tactics to manage both. In a two-year study in New York, two independent field trials were conducted concurrently. The first experiment included either a moderately thrips-resistant cultivar (‘Avalon’) or a thrips-susceptible cultivar (‘Bradley’), multiple nitrogen rates (0, 67, 84, 118, and 151 kg/ha) and either a season-long, action threshold-based insecticide program or no insecticide program (20 treatments total). The second experiment included the same cultivars and insecticide programs but evaluated phosphorous rates (0, 56, 112, and 168 kg/ha) (16 treatments total). In both trials and years, ‘Avalon’ experienced lower thrips densities, but suffered 58% more bacterial rot, which reduced onion yields overall by 9%. Nitrogen and phosphorus fertilizer had limited impact on onion thrips, bacterial rot, and onion yield. Although, higher rates of nitrogen fertilizer increased bacterial bulb rot in 2017. In both years, low rates of fertilizer (67 kg/ha N or 56 kg/ha P) produced statistically similar yields to plants supplemented with the highest rates of fertilizer. Insecticide use reduced thrips densities and increased bulb yield in both years but did not consistently reduce bacterial bulb rot. Therefore, growers can optimize onion production by reducing rates of fertilizer and using an action-threshold based insecticide program. Furthermore, our results indicate that IPM programs should be evaluated to consider multiple biotic constraints simultaneously within an agricultural production system as IPM tactics can be counterproductive.