Spatial variation and seasonal dynamics of Earias vittella (Fabricius) and its association with weather conditions in Himalayan okra-growing environments

The shoot and fruit borer, Earias vittella (Fabricius), is an important pest of okra, and its occurrence may vary considerably across contrasting agro-climatic environments. The present study assessed the spatial variation and seasonal population dynamics of E. vittella at selected low- and mid-hill locations of Himachal Pradesh, India, and examined associations between pest activity and prevailing weather conditions. Spatial observations were conducted at eight locations, while detailed seasonal observations were recorded at Palampur. Seasonal incidence of the okra shoot weevil, Alcidodes affaber Aurivillius, was additionally monitored at Palampur and Sujanpur Tira. Earias vittella infestation varied considerably among locations, with the highest late-fruiting infestation recorded at Sujanpur Tira (48.8%). At Palampur, fruit infestation increased from 2.1% on 13 August to a maximum of 18.7% on 18 September, while larval abundance reached 4.0 larvae plant –1 on the same date. Maximum and minimum temperatures showed strong negative associations with plant infestation and larval abundance at Sujanpur Tira and Bara, whereas relative humidity and rainfall generally showed weaker relationships. Shoot-weevil infestation showed a contrasting spatial pattern, reaching 47.1% at Palampur compared with 15.4% at Sujanpur Tira. The findings indicate substantial spatial and seasonal variation in pest activity and indicate that local agro-climatic conditions and crop phenology are important considerations for surveillance. Location-specific and phenology-based monitoring may therefore improve the timely assessment of pest pressure in Himalayan okra-growing environments.