POPULATION DYNAMICS AND INFESTATION PATTERNS OF MAJOR INSECT PESTS OF MAIZE IN RELATION TO ABIOTIC FACTORS

Abstract

Maize is a strategic cereal crop, but its productivity is reduced by recurring infestations of stem borers, fall armyworm and aphids. A field study was conducted at the Hazara Agriculture Research Station, Haripur, during the kharif season of 2024 to document the seasonal occurrence of Chilo partellus, Spodoptera frugiperda and Rhopalosiphum maidis and to examine their relationships with weather variables and selected natural enemies. Weekly observations were taken from crop establishment until maturity from replicated maize plots. Stem borer and fall armyworm damage were recorded as percentage damaged or infested plants, whereas aphids were counted as individuals per leaf. Weather variables included maximum and minimum temperature, morning and evening relative humidity, sunshine hours and rainfall. Stem borer appeared during the 29th standard meteorological week and reached a peak of 27.5% damaged plants during the 31st week. Fall armyworm also initiated during the 29th week and reached the highest infestation of 45.0% during the 31st week. Maize aphid appeared later, during the 33rd week, and peaked at 5.61 aphids per leaf during the 37th week. Minimum temperature and sunshine hours were positively associated with stem borer and fall armyworm incidence, while maximum temperature was positively associated with fall armyworm. Rainfall was negatively associated with aphid abundance. Aphid abundance increased together with spiders and ladybird beetles, while carabid larvae followed fall armyworm occurrence. These results show that pest pressure in Haripur maize is highly seasonal and weather sensitive. Timely scouting around the 29th to 37th standard meteorological weeks can support location-specific integrated pest management decisions.

Keywords: Zea mays; Chilo partellus; Spodoptera frugiperda; Rhopalosiphum maidis; weather factors; natural enemies; IPM.