Seasonal incidence of sucking pests and natural enemies in okra

Abstract

A study was conducted on the seasonal incidence of major sucking pests of okra and their natural enemies during spring-summer season of 2011 and 2012 at the District Seed Farm (AB Block) of Bidhan Chandra Krishi Viswavidhyalaya located at Kalyani, Nadia District, West Bengal. The results revealed that the leafhoppers first appeared in 2nd week of February (0.20−13 leaves) and reached a peak in the 3rd week of July (83.60 and 95.40−13 leaves in 2011 and 2012, respectively). Thereafter, the incidence reduced till the end of the cropping season. Aphids were observed in the first week but then showed a rise and fall with a peak during 1st week of July and 3rd week of June in 2011 and 2012, respectively. Incidence of whiteflies commenced from last week of January (0.07−13 leaves) and 1st week of February (0.13−13 leaves) during 2011 and 2012, respectively, which reached a peak population in the 1st week of June (3.97 and 3.03−13 leaves, respectively), and thereafter declined gradually till the end of the crop. Mites were first observed only from the 2nd week of March, and reached their peak in the 2nd and 1st week of June in 2011 and 2012, respectively. The coccinelid predator first appeared in the 3rd and 4th week, and reached a peak in the 3rd week of July and 3rd week of June (1.77 and 2.13−1plant) in 2011 and 2012, respectively. Chrysoperla was first observed from the last week and 3rd week of March and maintained a low population throughout. Correlation of seasonal incidence with maximum and minimum temperature, and morning and evening relative humidity revealed a positive relationship in case of leafhoppers, whiteflies, mites, coccinellids and Chrysoperla. Only the aphids had negative and non significant relationship with most weather parameters.