Recipient Organization
AGRICULTURAL RESEARCH SERVICE
800 BUCHANAN ST, RM 2020
BERKELEY,CA 94710-1105
Performing Department
(N/A)
Non Technical Summary
Alfalfa is one of the most important crops grown in the United States, as it provides vital feed for the dairy and livestock industries. However, Lygus bug is a major insect pest of alfalfa grown for seed and is an ongoing challenge for growers. Some effective pesticides that control Lygus are no longer widely available for use by alfalfa growers, and alternative pesticide options often come with other issues, such as negative impacts on beneficial insects. This can lead to detrimental impacts, such as the loss of insect predators of Lygus bugs or pollinators that are a vital part of alfalfa seed production. Therefore, alternative control measures for Lygus bugs are needed that are both effective at controlling this devastating pest and that minimize harm to beneficial insects. In this project, we will be testing alternative pesticides for their effectiveness in controlling Lygus bugs, and their impacts on beneficial insects such as predators of Lygus and pollinators. We will also be testing non-pesticide control options such as the use of biocontrol (e.g. parasitoid wasps) and physical barriers (e.g. netting) to reduce Lygus damage to the crop. The ultimate goal of this work is to provide alfalfa seed growers with effective Lygus control management recommendations that increase seed yields and minimize production costs. This project will be conducted with continuous input from alfalfa seed growers to ensure that our objectives and recommendations meet the needs of the industry.
Animal Health Component
90%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
0%
Goals / Objectives
Effective and efficient control of insect pests remains one of the major concerns for the agricultural industry. Growers' reliance on insecticides is nowhere more apparent than in alfalfa grown for seed. With recent concerns regarding insecticide resistance and off-target effects of insecticides on beneficial species, alfalfa seed growers are facing increasing pressure to effectively manage and protect commodities in all aspects of their farming operation. The goals of this project will be expanding availability of reduced-risk, selective insecticides to protect pollinators and other beneficial arthropods, along with developing new integrated pest management strategies for the continued sustainability of alfalfa grown for seed.For optimized production of alfalfa grown for seed, proper control of arthropod pests and pollinator health must be considered side-by-side. With the current restrictions and expected future loss of insecticide chemistries (organophosphates including chlorpyrifos) to control arthropod pests in alfalfa, growers are facing an uphill battle and uncertainties for production. We propose a multi-pronged IPM approach that encompasses four research objectives and two Extension/learning objectives that will generate new integrated pest management strategies for the control of the primary pest in this production system, Lygus bug. Proposed strategies will also prioritize the protection of pollinators (essential to seed production) and other beneficial arthropods (a vital part of Lygus control).Objective 1: Test chemical alternatives for Lygus bug control without the use of chlorpyrifos. We will examine both registered and unregistered but commercially viable insecticide compounds for their efficacy against Lygus bugs, as well as optimize timing and rates of insecticide application. This will be completed using a combination of both field and laboratory studies.Objective 2. Test the establishment of physical barriers to prevent adult migration of Lygus from fields of alfalfa produced for forage into fields of alfalfa produced for seed. This simple but effective method has been demonstrated to reduce the migration of pentatomid stink bugs in orchard systems in Washington State (Marshall 2020) and from forage alfalfa into cotton in the Southwest. By erecting temporary barriers when alfalfa forage hay is swathed, we may prevent a substantial number of Lygus adults from migrating into alfalfa seed fields. An additional benefit is that we will be able to quantify the migration of other beneficial, pest, or benign arthropods when they are captured in these passive barrier traps.Objective 3: Develop IPM strategies to increase efficacy of biological control measures for Lygus bug control. We will measure the efficacy of commercially available biological control measures including Anaphes spp. (parasitic wasps) and entomopathogenic fungi Beauveria bassiana, Isaria fumosorosea, and Metarhizium brunneum, all of which have been suggested as biorational and useful pathogens for Lygus bug control. We will also test the safety of selective versus broad-spectrum insecticides for natural enemies.Objective 4: Determine the safety for alfalfa leafcutting bees of insecticides useful for Lygus bug control. We will measure the sublethal effects from multiple insecticide chemistries used for Lygus bug control on alfalfa leafcutting bees, the most important managed pollinator in alfalfa seed production systems in the western region.Objective 5: Complete a comprehensive annual survey to provide insight on Integrated Pest Management practices employed to control problematic insect pests of alfalfa while protecting pollinators and other beneficial arthropods. Developing an appropriate integrated pest management program can be complicated and has become even more challenging as chemistries become unavailable. We will annually survey alfalfa seed producers regarding the timing of pesticide inputs, pollinator management, and production guidelines and analyze this information toward developing best management practices to be used in alfalfa seed production. The development and focus of this survey and subsequent analyses will be guided by grower stakeholders. This information will flow directly into Objective 6.Objective 6: Conduct an annual project evaluation with a focus group to quantify project value, assess grower behavior change, and pilot the subsequent year's research priorities based on project performance. Where the aforementioned survey in Objective 5 is largely quantitative, collecting many data points from a large number of growers, this follow-up objective is qualitative in nature, involving in-depth discussion with a highly engaged subset of stakeholders.
Project Methods
Objective 1: Study sites will be established at Washington State University to examine a suite of insecticidal compounds for control of Lygus bug. Using labeled recommendations, we will examine the highest and reduced labeled rate of each chemical compound for Lygus bug control, application timing, application method, and tank mixes of multiple compounds. The field trial will be arranged as a randomized complete block with 4 replications of treatments and an untreated control. Following applications, the plots will be sampled by sweep net pre-treatment and then 1, 4, 7, 10, 14, and 21 days post-treatment to determine which active ingredient(s), application timing(s), application method(s), and combination of insecticides controls Lygus bug effectively. Repeated measure analysis of variance will be calculated by treatment within field. If the results pass the F-test, pair-wise t-tests will be calculated for the abundance of adult Lygus bug and small and large nymphs in treated plots against the abundance of Lygus bug in untreated plots. Trials will be completed and recorded throughout all three years of our study.Objective 2: We will construct net barriers between alfalfa forage and alfalfa seed fields in four commercial alfalfa seed fields. The netting will be folded over itself at 1, 6, and 9 feet below the top and clipped to itself creating 6-inch insect capture flaps at those respective heights. Each barrier will be visually inspected 3 days after it has been drawn during forage alfalfa swathing events and the number of Lygus bugs and beneficials including bees will be quantified for both sides of the net barrier. At each site, both the forage and alfalfa seed fields will be sampled by sweep netting and the swathed status of the forage field. Lygus adults, flies, bees, weevil larvae and adults, aphids, caterpillars, ladybird beetles, and syrphid fly larvae will be counted. Seasonal trends will be analyzed using the mean number of Lygus bugs captured at each height in the barrier and in the sweep net samples on each post-swathing date. Treatment differences will be analyzed using PROC MIXED and PROC GLIMMIX. For the in-situ counts (barrier counts and trap counts), seasonal means of each treatment will be calculated and analyzed using analysis of variance with a normal distribution.Objective 3, Part 1: We will purchase parasitic wasps and entomopathogenic fungi from commercial vendors in the spring of 2024 and establish a randomized complete block field trial. Once an infestation of Lygus bug is noted, 15 field cages (6.2 x 6.2 x 2 m3) will be placed within the fields and treatments applied in three replications (4 experimental treatments - Anaphes, B. bassiana, I. fumosorosea, and M. brunneum, and 1 control treatment - nothing added/applied), using industry/label recommendations for the treatments. The plots will be sampled by stand counts at pre-application and then 4, 7, 10, 14, and 21 days post-treatment to determine which commercially available biological control methods exhibit efficacy as a Lygus bug control. We will use generalized linear mixed modeling (GLMMs) with a Poisson distribution conducted in R, lme4 package to test if treatments (biological controls) significantly reduce Lygus infestation numbers in cages. Treatment and sampling day will be included as fixed effects, and cage will be included as a random effect.Objective 3, Part 2: Geocoris and/or other alfalfa pest predators present in sufficient abundance will be collected and sorted into cohorts of between 5 and 10 individual insects. The beneficial arthropods will be treated with the Potter precision spray tower with serial dilutions of candidate insecticides. We will develop dose response curves for the beneficial arthropods to these candidate insecticides using Polo Probit™ software.Objective 3, Part 3: We will test the impact of the selective insecticide sulfoxaflor on the presence of natural enemies of Lygus bugs, including parasitoid wasps (Perestinus spp), big-eyed bugs (Geocoris spp.), minute pirate bugs (Orius spp.), spiders and carabid beetles. Similar fields grown by the same grower collaborators will be treated with either the synthetic pyrethroid bifenthrin or sulfoxaflor. These fields will be monitored weekly by sweep net through June of each year and the abundance of the beneficial arthropods detailed above as well as pest arthropods including Lygus bugs, alfalfa weevils, and aphids will be quantified. Larger 3rd to 5th instar Lygus bug nymphs will be dissected under a dissecting microscope for the presence of larval parasitoids. Counts of natural enemies and Lygus bugs will be compared between treatments using generalized linear mixed models (GLMMs) with a Poisson distribution. Counts of either natural enemies or Lygus will be analyzed separately, with the treatment and time post treatment included as fixed effects, and the field and managing grower included as random effects.Objective 4: We will use cage studies to determine if exposure to the insecticides sulfoxaflor and afidopyropen result in sublethal effects on alfalfa leafcutting bees, such as reduced foraging effort or reproductive output. Field cages will be erected over a planting of alfalfa. A polystyrene bee board will then be secured to a metal pole in each cage along with 40 male and 20 female alfalfa leafcutting bees. We will use videos to record foraging behavior pre- and post- applications, to evaluate sublethal impacts on the bees. To monitor nesting progress, nests will be x-rayed weekly, and the number of completed nests will be recorded. After the completion of the field trial, we will track the development of brood. We will also measure residues in alfalfa leaf pieces and nest provisions to determine field exposure levels. We will use generalized linear mixed models (GLMMs; package lme4 in R) to measure the effect of pesticide treatments and residue concentrations on each of the recorded behaviors. We will use a before-after control-impact (BACI) study design to determine if these behavioral data are affected by the fixed effects of week (before-after variable) and pesticide treatment (Table 2), with individual bee nested within cage included as a random effect to accounted for the repeated measures (e.g., BehavioralData ~ Week*Treatment + (1 Bee/Cage)). Objective 5: We will conduct a yearly workshop over the course of this project associated with the Western Alfalfa Seed Growers Association (WASGA) annual convention held each January to assess grower attitudes, practices, and learning. For approximately one hour, growers will be asked specific questions about the operation and demographics of their farm; the pest management practices they employ (including adoption of IPM practices such as sampling and economic thresholds); the number of pesticide applications made in the prior year for specific pests, diseases and weeds; and plans for pest management practices that may be employed the following year.Objective 6: We will recruit focus group participants from alfalfa seed growers and affiliated industry members in attendance at the WASGA annual conference. These participants will serve as a qualitative sounding board to provide additional, in-depth feedback. We will meet on the Tuesday afternoon in January directly following the conclusion of the annual WASGA meeting. This workgroup will discuss the results from the survey of growers completed on Monday morning at the convention. Following this we will have frank discussions on our prior year's research results followed by a planning session where we will formulate our subsequent year's project activities based on regional growers' input.