Date of Award:

5-1-1967

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Entomology

Committee Chair(s)

D. W. Davis

Committee

D. W. Davis

Committee

D. V. Sisson

Committee

J. R. Simmons

Abstract

The results of various laboratory tests have shown Megachile rotundata to be generally more resistant to insecticides than are Apis mellifera or Nomia melanderi. This greater resistance is not substantiated in field tests and observations, where M. rotundata appears to be highly susceptible to most insecticides. Its biological peculiarity of using alfalfa leaf cuttings for building cells may account for these conflicting results. Consequently, studies were initiated to determine the part played by the leaf cutting habit in the danger of insecticides to this bee. Two types of exposure were studied. In the first, either the source of nectar and pollen (Phacelia tanacetifolia Benth), or the source of leaves (prebloom alfalfa), were treated with insecticide. These plants were treated both in field and greenhouse cages. In the second type of exposure alfalfa plots were sprayed in a prebloom stage and M. rotundata were caged on them at a later date to test residual effect. The materials tested were: (1) malathion, (2) parathion, (3) DDT, (4) carbaryl, (5) diazinon, and (6) azinphosmethyl. Mortality counts of adult female bees were made at night by examining, before a light, waxed straws taken from the nest blocks. Mortality counts of larvae were made by opening the cells after they had reached the prepupal stage. Azinphos-methyl was very toxic, malathion and DDT moderately toxic, and parathion and carbaryl relatively non-toxic when applied to alfalfa leaves being used as nest material by M. rotundata. No conclusions were made from the limited data collected on diazinon.

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