Recipient Organization
MONTANA STATE UNIVERSITY
(N/A)
BOZEMAN,MT 59717
Performing Department
ANIMAL & RANGE SCIENCES
Non Technical Summary
Incorporating biopesticide into insect management plans can conserve natural enemies and pollinators. The purpose of this study is to examine the impact of several biopesticide products on alfalfa insect pests, natural enemies and pollinators.
Animal Health Component
50%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
The overall goal is to compare the effectiveness and environmental impacts of applications of three pesticides in seed alfalfa fields including; 1. Bifenthrin, a non-selective pyrethroid insecticide. Bifenthrin is commonly used to control lygus in alfalfa. However, it cannot be used during bloom or when natural enemies are present, and there is evidence of lygus bug evolving resistance against it (Grafton-Cardwell et al. 2005. 2. Novaluron, an insect growth regulator (chitin biosynthesis inhibitor). According to the EPA, although novaluron acts mainly by ingestion, it has some contact activity. It is 'comparatively safer to beneficial insects and [the] environment and is compatible for use in an integrated pest management system' (EPA 2001). Because the mode of action of novaluron is inhibition of chitin biosynthesis during molting (Staetz 2004), it should have little direct impact on adult natural enemies and pollinators. It is currently registered for use in
greenhouses. 3. Canola oil (low erucic acid rapeseed oil), a biopesticide that has a non-toxic mode of action for the target pests (that include aphids, caterpillars, and lygus bug (EPA 1998). Canola oil should have a low residual effect because of rapid decomposition (EPA 2005). It should also have no within-nest effects on developing bees. Nevertheless, it needs to be evaluated with respect to its physical effects on alfalfa blossoms and post-application bee foraging activity. Specific research objectives: R1. Evaluate the impact of reduced-risk insecticides on densities of lygus, aphids, and alfalfa weevils in seed alfalfa; R2. Evaluate the impact of reduced-risk insecticide treatments on densities of natural enemies; R3. Evaluate the impact of reduced-risk insecticide treatments on densities and activities of native and managed pollinator species; R4. Evaluate the impact of reduced-risk insecticide treatments on the quantity, quality, and species composition of floral resources
available to flower-visiting insects (both pollinators and natural enemies); and R5. Evaluate the impact of reduced-risk insecticide treatments on alfalfa seed damage and seed yield. Outreach Objectives O1. Develop specific guidelines for lygus management using novaluron and/or canola oil, perhaps in rotation with traditional insecticides such as bifenthrin; and O2. Develop an educational outreach program for adoption of reduced-risk insecticides in the seed alfalfa production system.
Project Methods
The research will be conducted at two irrigated commercial seed alfalfa farms in Montana. Treatments will include applications of bifenthrin at a rate of 5.0 oz. per acre, novaluron applied at a rate of 8.0 oz. per acre, and canola oil at a rate of 1076 oz. per acre. One spray application will be timed to correspond with the first lygus hatch of each year, which usually occurs in late June or early July and is also the most synchronous and damaging to the alfalfa seed crop. The second application will coincide with peak occurrence of nymphal instars III and IV. Choice of insects to be sampled and counted, is based on preliminary data. Recent work in our labs has included assembling reference collections for all of the groups of insects listed below. The main focus of the study will be Lygus spp., Orius, Nabis, Geocoris, and Peristenus spp. (important parasitoids of lygus bugs), and Megachile rotundata. Because of the variety of insects to be sampled, we will use five
sampling methods to assess the composition of pollinator communities. Data on insect abundance and diversity will be analyzed using 1) repeated measure analyses of variance with insecticide treatment as the between-treatment factor and date as the within-treatment factor; 2) diversity indices, and 3) ordination (nonmetric multidimensional scaling; using PC-ORD. Pollinators, including M. rotundata, forage across much greater distances than the sizes of our plots. Pollinator include repellency, decrease in numbers and activity. We will use visual surveys to directly assess the rates of visitation to alfalfa flowers and an indirect method, assessing pollen loads carried by females. Counts of different pollen types will allow us to determine the frequency distribution of pollen types and the number of pollen grains carried by each female. Effects of insecticides on pollinators can also be manifested within nests, where developing bees may be exposed to contaminated pollen and nectar
transported to the nest by adult females. Small blocks of nest arrays will be placed in the center of each plot and prior to harvest, the nest blocks will be returned to the lab for examination. Flowers species will be surveyed along three transects in each plot. To assess alfalfa flower density, we will record 1) the density of mature, untripped alfalfa blossoms in each plot, and 2) the proportion of recently tripped blossoms. Alfalfa stem density per unit area will be recorded early in the growing season. After harvest stem samples will be taken to assess seed production and lygus damage. The project will provide information on 1) conservation of natural enemies and pollinators, 2) natural enemy/pest ratios, and 3) effects of pesticide use on pollinator activity and pollen sources for leafcutting bees.