Date of Award:
5-1-1993
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Biology
Department name when degree awarded
Biology
Committee Chair(s)
Diane G. Alston
Committee
Diane G. Alston
Committee
Vincent J. Tepedino
Committee
Edward W. Evans
Committee
Kimberly A. Sullivan
Abstract
Reproduction by entomophilous, endangered plant species may be threatened by insecticide applications if these applications are shown to have detrimental effects on pollinators. Pediocactus sileri Benson is one endangered plant that may be affected by carbaryl bran bait (2% A.I.) applications currently being considered for use on the rangelands of the Arizona Strip. This study was conducted to determine the potential effects of carbaryl bran bait applications on the pollination of P. sileri. In an experiment designed to reduce pollinator visits by 2/3 to 4/5, P. sileri was not shown to be pollinator limited. Therefore, reductions in P. sileri pollinator populations may not be accompanied by reduced P. sileri reproduction. Twenty species of native, solitary bees were collected visiting P. sileri. Ashmeadiella and Dialictus were the most abundant genera collected. P. sileri visitors were collected from early April to late June, the time period coinciding with optimal grasshopper control. Timing insecticide applications to have a minimal effect on P. sileri pollinators may, therefore, be difficult. Attempts to determine the distances that native bees commonly fly were unsuccessful. This information would help provide a recommendation for the size of insecticide-free buffer zones around endangered plant populations. Experiments conducted to determine the lethal effects of carbaryl bran bait on a representative bee species, Megachile rotundata Fabricius, revealed no harmful effects on adult bees. M. rotundata larvae fed provisions contaminated with 2 mg or 1 mg of carbaryl bran bait did experience greater mortality than those fed uncontaminated provisions. Both doses, however, are large and unlikely to be encountered in nature. Carbaryl bran bait appears to be nontoxic to M. rotundata at levels likely to occur in the field. No sublethal effects of bait on adult, female M. rotundata were apparent as measured by the number of days spent nesting, number of nest cells produced, rate of cell production, offspring weight, investment in offspring, or offspring sex ratios. Additionally, no effects through time were evident. Finally, no sublethal effects on larval M. rotundata were obvious. Larvae fed contaminated provisions gained as much weight as those fed uncontaminated provisions.
Recommended Citation
Peach, Matthew, "The Lethal and Sublethal Effects of Carbaryl Bran Bait on a Representative Pollinator of Rare Plants, The Alfalfa Leafcutting Bee (Hegachile rotundata F.), And Potential Effects on the Reproduction of the Endangered Plant, Pediocactus sileri Benson" (1993). Biology. 600.
https://digitalcommons.usu.edu/etd_biology/600
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