Bioecology of potato tuber moth, Phthorimaea operculella Zeller in mid hills of Himachal Pradesh

Potato tuber moth (Phthorimaea operculella Zeller) passes through seven generations annually in Kangra valley. Adult emergence begins after February from hibernating larvae of previous year. As the temperature rises to 17.5°C eggs are laid on potato leaves and the infestation gradually progresses with further rise in temperature. Eggs were white in colour measuring 0.39 × 0.33 mm in length × breadth and hatched in 4–10 days. Each larva passed through four instars. The body length × head width was 0.67 mm × 0.16 mm, 3.05 mm × 0.30 mm, 5.34 mm × 0.59 mm and 10.49 mm × 1.11 mm in the respective instars. Total larval period occupied 12–24 days from March–October upto 6th generation. However, in 7^th generation, 4^th instar larva hibernates, hence total larval period occupied 130–134 days from December–February. Pupal period varied from 5 to 30 days and the total life cycle was completed in 21–44 days from March–October. But, in 7^th generation, pest over winters completing its life cycle in 162.05 days. Average developmental 4^th period was minimum during June–july in generation. The diurnal fluctuations in temperature from 23–24°C are most favourable for this species.