Date of Award:

5-1-1983

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

Donald W. Davis

Committee

Donald W. Davis

Committee

Clive D. Jorgensen

Committee

Donald V. Sisson

Committee

Sherman V. Thomson

Committee

Wilford J. Hanson

Abstract

The biology of Quadraspidiotus perniciosus (Comstock) and its parasite, Aphytis nr. vandenboschi DeBach and Rosen, was studied. Q. perniciosus developmental time declined substantially with each increase in temperature between 18.3 and 31.0°C. Constant temperatures between 10.0 and 15.6°C or above 31°C were detrimental to A. nr. vandenboschi. The mean number of eggs laid per parasite was 12.08 at 23.8°C and 11.58 at 25.6°C. Under experimental conditions the parasite did not discriminate between previously parasitized hosts and unparasitized ones. Field investigations were in two unsprayed apple orchards, one at Brigham City and one at Hyde Park, Utah. Both male San Jose scales and female parasites responded well to the synthetic San Jose scale sex pheromone. There were no significant differences between numbers of either male San Jose scales or female parasites caught 2 m or at 4 m trap heights. All stages of San Jose scale were present throughout the spring and summer. The scales overwintered mainly as blackcaps and produced basically two generations per year. A. nr. vandenboschi was the only parasite of the San Jose scale detected at both Brigham City and Hyde Park. It passed the winter as pupae and produced three generations per one of Q. perniciosus. Parasitism reached the highest level in September 1981 when 83.3% of the adult female scales on foliage were parasitized at Brigham City. Both San Jose scale and parasite data from the Hyde Park orchard were less reliable than those from the Brigham City orchard. A predatory mite, Pyemotes herfsi (Oudemans) was the principal factor in the reduction of A. nr. vandenboschi populations under field conditions. during July and August at Brigham City and in laboratory cultures.

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .