Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Includes bibliographical references. Issued in print and online. Available via ProQuest Digital Dissertations.

Honey bees (Apis mellifera L.) were exposed to six pyrethroid insecticides using four application techniques. Toxicities of the insecticides were compared. Results of topical and contact tests placed the six pyrethroids in one of three categories based on their relative toxicity to honey bees; highly toxic (cyfluthrin, cypermethrin, and permethrin), moderately toxic (flucythrinate and fenvalerate), and non-toxic (fluvalinate). The residue tests, by contrast, simulated field conditions by using sprayed cotton leaves for exposure. This test showed that both compound and formulation played an important role in determining toxicity. The conditioning test combined some of the previously used techniques and refined them into a test for detecting behavioral changes to bees following sublethal exposure to pesticides. Insecticide-treated honey bees had a lower learning curve than their respective control group. This indicates that, although bees may survive poisoning from pesticides, certain physiological functions are affected.

Part I: In the first study of pyrethroids, twenty-one novel pyrethroid esters bearing strong electron-withdrawing groups (e.g., halomethylketo and nitro groups) in the double bond side chain of the cyclopropane acid moiety have been synthesized and evaluated for insect toxicity. Rather than the usually employed Wittig reaction for these syntheses, the novel pyrethroid acid moieties were prepared by amino acidcatalyzed Knoevenagel condensations under mild conditions. In the second study of pyrethroids, fourteen pyrethroid-like carbonates were synthesized by condensation of a variety of alcohols and the chloroformates of the corresponding known pyrethroid alcohols.

No description available.

A laboratory selected strain of Heliothis virescens demonstrating a 400-fold resistance to permethrin exhibited no differences in penetration and only a slight enhancement of metabolism when compared with a susceptible strain. Synergism with piperonyl butoxide and DEF produced similar synergist ratios for the resistant and susceptible strains, but the resistant strain showed a much larger synergist difference. Thin layer chromatography of extracts from larvae dosed with 14C-labelled permethrin demonstrated a small increase in metabolism of the cis-isomer by the resistant strain, but no differences in metabolism of the trans-isomer. The synergism study and the 14C-labelled permethrin experiment both indicate that there is a small increase in metabolism of permethrin in the resistant strain, but not enough to account for the greatly increased LD50 value. Cross-resistance to DDT indicated that target site insensitivity may play a major role in resistance to pyrethroids in this strain.

No description available.

No description available.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 168-181). Also available on the World Wide Web.

Pyrethroid-resistant Hyalella azteca with genetically-confirmed voltage gated sodium channel mutations were identified at three geographically isolated locations in Central California. In December 2013, H. azteca were collected from Mosher Slough in Stockton, CA, a site with reported pyrethroid concentrations at approximately twice the LC50 for laboratory-cultured H. azteca and shipped to Southern Illinois University Carbondale. These H. azteca have been maintained in pyrethroid-free culture since December, 2013 with one supplement of organisms from the same site in March, 2014. Abundant research exists on fitness costs of insecticide resistance to pest species including reduced fecundity, fertility, reduced overwintering success, and reduced survival to adulthood. The current study showed that after 22 months in culture, resistant animals had approximately 53 times higher tolerance to permethrin than non-resistant H. azteca. After 16 months in culture, the resistant animals maintained complete loss of the wild-type allele at the L925 locus and had non-synonymous substitutions that resulted in either a leucine-isoleucine or leucine-valine substitution. Finally, the resistant animals showed lower reproduction, lower upper thermal tolerance, and were more sensitive to the common contaminants DDT, copper (II) sulfate, and NaCl. As shredders that consume epiphytes, animal and plant detritus, and filamentous algae, H. azteca aid in nutrient cycling through the breakdown and fragmentation of detritus and can serve as an important food source for larger invertebrates, fish, amphibians, and waterfowl. The results of the current study also hold implications for biomonitoring programs, toxicity testing, and laboratory culture procedures, as cryptic species complexes with varied sensitivities could dramatically alter results of these programs.

Chronic exposure to pyrethroid insecticides can result in sublethal impacts to non-target species in aquatic systems, driving population-level changes. Characterizing the underlying mechanisms of resistance is essential to better understanding the role and potential consequences of contaminant-driven microevolution. The current study found that multiple mechanisms enhance the overall phenotypic expression of resistance characteristics in Hyalella azteca. In VGSC mutated H. azteca, both adaptation and acclimation traits appear to play a role in the attenuation of the adverse effects to pyrethroid exposures. Pyrethroid resistance is primarily attributed to the heritable mutation at various loci of the voltage-gated sodium channel, resulting in reduced target-site sensitivity. However, some additional reduced pyrethroid sensitivity was also conferred through reversible physiological responses to environmental conditions, such as enhanced enzyme-mediated detoxification. Cytochrome p450 monooxygenases (CYP450) and general esterases (GE) were the biotransformation pathways that significantly contributed to the detoxification of permethrin in H. azteca. Over time, VGSC mutated H. azteca retained most of their pyrethroid resistance, though there was some increased sensitivity from parent to offspring when reared in the absence of pyrethroid exposure. The permethrin 96 h LC50 declined from 1809 ng/L in P0 individuals to 1123 ng/L in the F1 generation, though still remained well above the 20.4 ng/L of wild-type individuals. This reduction in tolerance was likely related to alterations in acclimation mechanisms conferring resistance traits, rather than changes to target-site sensitivity. Enzyme bioassays indicated decreased CYP450 and GE enzyme activity from P0 to F1, whereas the VGSC mutation was retained. The permethrin LC50 values in resistant H. azteca were still two orders-of-magnitude higher than non-resistant populations indicating that the largest proportion of resistance was maintained through the inherited VGSC mutation. Thus, some variation in phenotypic expression of resistance characteristics in H. azteca over time is likely associated with uninheritable genetic factors or non-constitutively expressed traits controlling enzyme pathways which overlie a strong heritable component of resistance. A better understanding of the mechanistic and genomic basis of variable acclimation will be necessary for better predicting the ecological and evolutionarily consequences of contaminant-driven change in H. azteca.