Ecological investigations on the potato tuber moth, Phthorimaea operculella (Zeller)(Lepidoptera: Gelechiidae).
The influence of some environmental factors on the biology of Phthorimaea operculella (Zell.) was investigated in the laboratory in South Africa. Eggs hatched at 11 deg C, with the lower threshold of development at 9.5 deg C, and required about 1550 hour-degrees C. to hatch. Development and adult emergence were not influenced by relative humidity, and larval mortality was generally low, up to 96% of the larvae surviving under optimal conditions to pupate. Temperature influenced pupal development but relative humidity did not. High light intensity inhibited egg laying, and the optimal temperatures for oviposition lay between 20 and 30 deg C. The potato plant is an excellent food-plant for P. operculella, but Datura stramonium and other solanaceous plants are sometimes attacked. Native plants are not important in maintaining populations of P. operculella in the Transvaal because larval development continues throughout the winter on the Transvaal Highveld in tubers that have been overlooked at harvest, and this facilitates carry-over on to the new crop.