Date of Award:

5-1-1984

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

William A. Brindley

Committee

William A. Brindley

Committee

D. W. Davis

Committee

W. J. Hanson

Committee

D. L. Turner

Committee

R. P. Sharma

Abstract

Endosulfan susceptibility and synergism with DEF (S.S.S-tributylphosphorotrithioate) and PB (piperonyl butoxide) for different strains of adult apterous spotted alfalfa aphids were examined in addition to evaluating the correlation between esterases and the aphid's tolerance or resistance to endosulfan. Unsynergized endosulfan LC50 values for populations of spotted alfalfa aphids from near Delta, Utah, Nampa, Idaho or Nyssa, Oregon, were 57.56, 37.51 and 45.60 µg/vial, respectively, while pretreatment with DEF reduced the LC50 values to 3.32, 3.2 and 4.73 µg/vial respectively. PB had either little synergistic or antagonistic effects on the endosulfan toxicity. Senergistic data suggested the dominance of esterases as detoxifying systems in T. maculata. Four esterases were detected in spotted alfalfa aphids from near Nampa while 6 esterases were found in spotted alfalfa aphids from near Delta. Based on the inhibition by eserine sulfate and dichlorovos (DDVP) they were classified as one cholinesterse and remaning carboxylesterase. Noticeable differences in the migration and staining intensity were detected between Delta and Nampa strains. Spotted alfalfa aphids from Delta showed considerably higher hydrolyzing ability toward 1-naphthyl acetate or proprionate and 2-naphthyl acetate than their Nampa counterpart. No significant difference in I50 values of the field collected samples of the two strains were found. Nevertheless, there was a dramatic increase in I50 values of the Delta greenhouse satrain after four generations of screening with endosulfan. Esterases hydrolyzing naphthyl acetates may be reasonable markers for individual spotted alfalfa aphids with resistance attributes. Finally, the Delta strain showed high cholineserase activity toward acetylthiocholine substrate and less sensitivity to eserine sulfate inhibition, in comparison to its Nampa counterpart which might suggest a minor role in resistance of the Delta population.

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