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United States Department of Agriculture

Agricultural Research Service

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Research Project: Effects of Pest Management Practices on Pests and Alfalfa Leafcutting Bees in Alfalfa Seed

Location: Pollinating Insect-biology, Management, Systematics Research

Project Number: 2080-21000-015-20-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2014
End Date: May 30, 2018

More insecticide applications are made for control of lygus bugs than for any other insect attacking alfalfa seed in southwest Idaho. Many of these compounds are broad-spectrum organophosphates, carbamates and pyrethroids that have significant toxicity to alfalfa leafcutting bees. Several lower-risk insecticides have received section 3 labels for use in alfalfa seed: novaluron (Rimon 0.83 EC), acetamiprid (Assail 70 WP) and flonicamid (Beleaf 50 SG), and others (e.g. sulfoxaflor (Transform) and flupyradifurone (Sivanto) currently are undergoing evaluation for efficacy and impact on alfalfa leafcutting bees (ALCB) and may be labeled for use on alfalfa seed. The proposed work provides the local and regional alfalfa seed industry with information concerning the efficacy of these and other compounds against lygus bugs and other alfalfa seed pests, including pea, blue alfalfa and spotted alfalfa aphids, and on the safety of these compounds to (ALCB) and important natural enemies of alfalfa seed pests. I will 1) conduct laboratory, greenhouse, and/or field experiments examining the efficacy of currently labeled and new insecticides against lygus bugs and other pests of alfalfa, and 2) conduct laboratory, field, and/or greenhouse experiments to examine the impact of currently labeled new insecticides on the activity of ALCB and natural enemies of alfalfa seed pests. Year 2: 1. Conduct laboratory, greenhouse, and/or field experiments examining the efficacy of currently labeled and new insecticides against lygus bugs, aphids and other pests of alfalfa. In 2016 our focus will continue to be on bee safety of Transform, and on trials begun in 2015 evaluating the efficacy of low (2.8 oz./ acre) vs. high (4.2 oz./ acre) rates of Beleaf against Lygus bugs and aphids. 2. Conduct laboratory, field, and/or greenhouse experiments to examine the impact of currently labeled and unlabeled insecticides (e.g. Beleaf at the high rate of 4.2 oz./ acre, and Transform) on the activity of ALCB: lack of bee safety data was cited in the cancelation of Transform.

(See original documents for Year 1 approach) 1)Experiments will be conducted at the Parma Research and Extension Center in Parma ID (UI Parma) or in grower fields in southwest Idaho that compare the efficacy against lygus bugs of individual and combinations of currently labeled (e.g. Beleaf, Rimon) and experimental/ unlabeled compounds (i.e. Transform, Beleaf @ 4.2 oz./acre). An untreated control and standard bloom period applications of dibrom, Bifenthrin, or dibrom plus Beleaf will be included in all trials. The bloom period treatments in all experiments will be proceeded by pre- bloom clean-up applications (e.g., lamda cyhalothrin) applied 5 to 7 days prior to alfalfa leafcutting bee release. Studies will be conducted on 0.01 (minimum size) acre plots of established alfalfa seed with plots arranged in a randomized complete block design with four replications and an 11ft.buffer between plots. Foliar broadcast applications will be made using a tractor-drawn boom sprayer or CO2 pressurized sprayer calibrated to apply 30 gpa at 32 psi using 8002VS flat fan nozzles on 22" spacing. Lygus bug and natural enemy abundance will be estimated prior to and 7, 14, 21, and 28 days after treatment by taking three, 180-degree sweep from each plot on each date (on larger plots 5 sweeps per plot will be used). The number of pea aphids + blue alfalfa aphids, and spotted alfalfa aphids also will be recorded. Yield (lbs/acre) will be collected from each plot. All registered materials will be applied according to label specifications. 2)Replicated experiments will be conducted in the laboratory using field-treated alfalfa foliage to determine the residual toxicity of selected alternative pesticides and pesticide tank mixes to adult alfalfa leafcutting bees. Insecticides will be applied labeled or anticipated labeled field rates with a CO2 pressurized sprayer 114 l (30 gallons) per acre using a hand-held boom with 4 nozzles applied to 0.01 acre plots of first or second growth alfalfa. The untreated control will consist of a similar plot treated with water only. Field-weathered residual test exposures of 2 hr, 8 hr, 24 hr, 48 hr and 96 hr will be replicated 4 times with 4 foliage samples per treatment and time interval. Foliage samples consisting of about 500 cm of foliage taken from the upper 15 cm portions of plants clipped to 2.5-cm lengths will be placed into cages constructed from plastic Petri dishes (15 cm diameter) whose tops and bottoms are separated by a wire screen (6.7 meshes/cm) insert (45 cm long and 5 cm wide). Alfalfa leaf cutting bees used in studies will be collected from an insecticide-free alfalfa seed field at the UI Parma or from grower fields, anesthetized with CO2 and placed into cages. Insects in cages will be provided syrup (1:1 sucrose: water) in a wad of cotton (5 x 5 cm), and held at 27' C for 24 hour mortality counts and residual toxicity values will be calculated.

Last Modified: 06/25/2017
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