A presence-absence sampling plan for pink bollworm Pectinophora gossypiella (Saunders), was developed to provide a more accurate index of moth activity. A field validation of this plan proved a better simulation of the field-collected data.

Cotton plant phenology affected the egg distribution patterns and female moths oviposited principally on vegetative cotton parts until mid-July and on vegetative parts and cotton bolls until August and principally on the cotton bolls thereafter. Two to three week-old bolls were the most preferable for oviposition. Eggs on bolls were placed on the inside surface of bracts or under the calyx.

Different application programs based on egg sampling and larval-age structure in comparison with the conventional automatic spray system were evaluated for their initial effects (boll infestation and cotton yield) and latent effects (population density in the following season) to determine whether egg-sampling or larval egg-structure methods rather than the conventional method provided more optimal timing of control.

Improved timing of insecticidal applications, coinciding with egg population peaks, resulted in reduced boll infestation, highest cotton yield and lowest population density in the following season. Applications on the basis of larval age-structure reduced the use of insecticide thus giving better results. An increased number of applications also showed pronounced effects when properly timed and suitably distributed through the cotton season. Improper timing of application gave bad results regardless of the number of applications. An automatic spray schedule showed negative effects in comparison to the untreated check because of lack of proper timing of application.