Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
2 results
Search Results
Item Exposure and risk to non-target receptors for agricultural spray drift of formulation types and adjuvants(Montana State University - Bozeman, College of Agriculture, 2017) Preftakes, Collin James; Chairperson, Graduate Committee: Robert K. D. Peterson; Jerome J. Schleier III, David K. Weaver, Greg Kruger, Ryan Henry and Robert K. D. Peterson were co-authors of the article, 'Effect of insecticide formulation and adjuvant combination on agricultural spray drift' which is contained within this thesis.; Jerome J. Schleier III, David K. Weaver and Robert K. D. Peterson were co-authors of the article, 'Non-target insect risk assessment of drift reduction insecticide formulations and spray adjuvants' which is contained within this thesis.Agricultural applications of crop protection products can have negative economic and ecological consequences when spray drift occurs. Among the ways to reduce spray drift is to manipulate the physical properties of the spray solution with formulated products and tank additives, but further research is required to better understand their effects. By measuring spray drift under field conditions and using the results to estimate ecological risk, we characterize the effect on drift for two formulation types and two adjuvants. A field study was conducted where off-target ground deposition and droplet size were measured to indicate spray drift for different combinations of the formulations and adjuvants, accounting for environmental conditions. Each treatment combination was also sprayed in a wind tunnel set up to precisely measure droplet spectra so that these could be related to deposition in the field. Finally, an efficacy experiment was conducted to test for tradeoffs between drift reduction and pest control. Results from the field study suggest that as much as 32% drift reduction was achieved by selecting between the tested formulation types, and as much as 62% by incorporating certain spray adjuvants, but this effect depended on the formulation/adjuvant combination. Treatments with smaller droplet sizes had greater drift, and there was no tradeoff between drift reduction and pest control. We assessed ecological risk for terrestrial insects in non-target habitats using a novel approach to estimate insecticide residue on plant surfaces based on ground deposition data from the field study. Exposure concentrations were combined with a cumulative distribution of species sensitivities to statistically represent the risk of toxicity for the active ingredient that was used and the levels of drift that were observed. We found that substantial reductions in the percentage of insect species affected in an off-target area could be achieved by certain formulation types and adjuvants. This work could be useful for developing a classification scheme for formulated products and tank additives based on their potential for reducing spray drift and ecological risk to non-target receptors.Item Toxicity, exposure, and risk of insecticides used for mosquito management on the alfalfa leafcutting bee, Megachile rotundata(Montana State University - Bozeman, College of Agriculture, 2017) Piccolomini, Alyssa Margaret; Chairperson, Graduate Committee: Robert K. D. Peterson; Shavonn R. Whiten, Michelle L. Flenniken, Kevin M. O'Neill and Robert K. D. Peterson were co-authors of the article, 'Acute toxicity of permethrin, deltamethrin, and etofenprox to the alfalfa leafcutting bee, Megachile rotundata (Hymenoptera: Megachilidae)' which is contained within this thesis.; Michelle L. Flenniken, Kevin M. O'Neill and Robert K. D. Peterson were co-authors of the article, 'Leaf residue toxicity and risk of mosquito insecticides to the bees, Megachile rotundata and Apis mellifera' which is contained within this thesis.; Michelle L. Flenniken, Kevin M. O'Neill, Ruth P. O'Neill, Casey M. Delphia and Robert K. D. Peterson were co-authors of the article, 'The effects of an ultra-low-volume application of etofenprox for mosquito management on Megachile rotundata (Hymenoptera: Megachilidae) larvae and adults in an agricultural setting' which is contained within this thesis.The alfalfa leafcutting bee, Megachile rotundata F. (Hymenoptera: Megachilidae), is one of the most managed solitary bees and is an important pollinator of many crops, especially alfalfa, Medicago sativa L. However, little is known about its response to insecticides, specifically pyrethroids, which are frequently used to manage populations of adult mosquitoes that inhabit the same areas. Current regulatory requirements for insecticide toxicity to non-target insects focus on one pollinator, the honey bee, Apis mellifera L., but this species does not represent all insect pollinator species in terms of response to insecticides. Therefore, we characterized the toxicity and risk of three pyrethroid insecticides (permethrin, deltamethrin, and etofenprox) on adult M. rotundata in both laboratory and field settings. The median lethal dose, LD 50, was estimated for adult M. rotundata females when exposed to each pyrethroid to serve as a baseline toxicity test to determine the susceptibility of M. rotundata to these insecticides. The range of concentrations for permethrin and etofenprox ranged from 0.0075-0.076 microgram/bee and the range for deltamethrin was 0.0014-0.0075 microgram/bee. The estimated LD 50 results for permethrin, etofenprox, and deltamethrin were 0.057, 0.051, and 0.0016 microgram/bee, respectively. After obtaining the LD 50 values, we compared female respiration rates after dosing of each LD 50 endpoint. In a field study, we applied a formulated version of each active ingredient at the maximum labeled rate of 0.017 kg/ha over an alfalfa field via ultra-low-volume (ULV) applicator and observed mortality of both adult A. mellifera and M. rotundata for 48-hr after exposure. In both species, there was no significant difference in mortality between control and treated groups for any of the formulations. In another field study, a formulated version of etofenprox was applied in an alfalfa field at the half-maximum labeled rate of 0.003 kg/ha and directly targeted to M. rotundata nests. There was no significant difference in mortality between control and treated groups. We also did not observe a significant difference in the number of adults reared between treated vs. control shelters. Results from the field studies suggest that the risk of mortality from these insecticides applied via ULV applicators may be relatively low.