Limitations in the use of thermal summation for describing the activity of pink bollworm, Pectinophora gossypiella (Saunders), in relation to phenology of Upland cotton in Punjab

Abstract

An attempt was made to apply the concept of degree-days on the moth emergence of diapausing larvae of pink bollworm, Pectinophora gossypiella as well as to relate its infestation with the crop phenology of Gossypium hirsutum cv. F 414, sown on three different dates in Punjab. Utility of degree-days was found to be limited in predicting the peaks of moth emergence during late June-early August, probably owing to extremes of high temperature (> 40°C) in May-June. The critical period of boll formation in terms of accumulated heat units (developmental zero: 15.5°C and January 1 as base) was found to be 1795-2385, 2134-2427 and 2190-2470 for the first (late April), second (late May) and third (late June) sowings, respectively. Keeping in view the peaks of moth emergence from diapausing larvae and the period of pink bollworm infestation vis-à-vis boll formation, control strategy against this pest has been suggested.