Item

Some aspects of the reproductive biology and chemosterilisation of the potato moth, Phthorimaea operculella (Zeller) (Gelechiidae: Lepidoptera) : A thesis submitted for the degree of Doctor of Philosophy, University of Canterbury [Lincoln College]

Nabi, Mohammad Nur
Date
1978
Type
Thesis
Fields of Research
ANZSRC::300804 Horticultural crop protection (incl. pests, diseases and weeds)
Abstract
A report of a study on some aspects of reproductive biology and chemosterilisation of the: potato moth is presented. Investigation on reproductive ·biology comprises mating, egg laying, adult body weight, adult longevity, sperm activity and fertility. Mating occurred in this moth within 24 hours of eclosion and they are polygamous; however, single mating was more often than multiple mating or lack of mating. Moths which lived longer mated more often. No strong relationship was found between moths' body weight and mating number. Egg laying by females was found to be related to many factors: mating, body_ weight, longevity, temperature, photoperiodism and kind, colour and position of the substrates. On average, more eggs were laid by mated females than unmated females. Two kinds of sperm - apyrene and eupyrene - were found in this moth. In each mating, a single sperrnatophore was passed to female. Containing both types of sperm. Sperm storage was observed in males in the duplex and in the mated females in the sperrnatheca. The fertility of eggs was more than 90 per cent. The duration of sperm survival was found to be from one to 12 days after mating, determined by egg hatching. Parthenogenetic reproduction in the tested females was nil. The chemosterilants thiotepa and hempa were used in circulatory fumigation chambers for male and female sterilisation. In biological testing, eggs laid, eggs hatched, longevity of treated moths and their partners, and mating were determined. Thiotepa was extensively studied for its persistence (in biological testing) and effects of abiotic factors such as temperature, exposure time and concentration. This compound did not lose its sterilant activity when used successively up to five times during the same day or once weekly for a total of four weeks. The sterilant activity was related to temperature, exposure time, concentration and rate of airflow of the circulatory fumigation chamber. It was possible to sterilise fully male and female moths without adverse effects on mating and longevity. Generally, males were more susceptible to sterilisation than females. No definite relationship of egg laying, longevity of moths and mating with dose level used was found and they were unaffected in comparison to the control groups. The effect of inherited sterility was determined and it was found that some reduction of fertility was observed; however, no complete sterility was observed in the adults of F1 generation which were paired with untreated moths of the opposite sex. The mating competitiveness of sterilised males showed that two sterile males were equally competitive with a single male to a single female in the laboratory test. The longevity and mating appeared to be unaffected in this competition. Mating competition studies in the field cages with sterile males and normal males to untreated females showed that sterile males were slightly less competitive than the test in the laboratory; however, they were effective in suppressing the population in the cages in comparison to the control. Investigation on the sterilant activity of hempa on potato moth revealed that this chemical was less effective than thiotepa. A limited sterility effect on male and female potato moths led to the limitation of experimentation with this compound effect was little higher on males than females.
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