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Thesis (M.S.)—University of Nebraska—Lincoln, 1972. Department of Entomology.


Copyright 1972, the author. Used by permission.


This study was divided into four major experiments. All the studies were conducted at the North Platte Experiment Station from beetles collected near North Platte. The purpose of the first experiment was to determine the susceptibility of field collected WCR beetles to Bux0, diazinon and thimet. The second experiment was conducted to examine the effects of age on beetle resistance to these insecticides and to see whether the LD50 values of beetles of known age were comparable to those of beetles of unknown or mixed ages. The third experiment was undertaken to find out if significant differences in LD50 values existed between male and female WCR beetles. The fourth experiment was conducted to ascertain the effect of photoperiod on beetle susceptibility to diazinon, thimet and Bux0.

The test methods used for the four experiments were basically the same. Briefly, the beetles were collected from corn plants with a specifically modified vacuum cleaner powered by a portable electric generator. After collecting, the beetles were placed in holding cages and provided with corn silk and water. The WCR beetles were always treated within 24 hours of collection. Six to eight test doses were used to assey each insecticide. Twenty insects (two replicates of ten beetles each) were used for each test dose. For all tests twenty beetles were treated with acetone and served as controls. The controls functioned to indicate that the acetone solvent was not toxic and to assure that all test equipment was free of insecticide contamination.

Advisor: Harold J. Ball