Bioecology and management of rice hispa Dicladispa armigera Oliver under mid hill conditions of Himachal Pradesh

Abstract

newline Detailed studies on rice hispa, Dicladispa armigera (Oliver) were undertaken at CSK Himachal Pradesh Krishi Vishvidyalaya, Rice and Wheat Research Centre, Malan during 2014-2016. The studies included understanding rice hispa s annual life cycle, its population build-up, assessment of losses inflicted and management with suitable insecticides and biopesticides. The life history of D. armigera consisted of four distinct stages viz. egg, grub, pupa and adult, each having an average duration of 4.5, 14.0, 9.1 and 22.4 (male); 38.7 (female) days, respectively. Both adults and grubs caused damage due to its feeding on paddy leaves. As many as 3-4 generations were recorded under laboratory conditions (mid June-mid November), but the adults of last generation failed to lay eggs. A few individuals of adults of last generation survived on rice seedlings and weed host, Cynodon dactylon (Linn.) till April-May with limited feeding and no egg-laying. Field observations recorded the incidence of hispa adults on wheat crop during February-April. With the early monsoon showers, the adults of hispa started appearing on weeds viz. C. dactylon, Cyperus rotundus (Linn.), Andropogon gayanus (Kunth), Digitaria sanguinalis (Linn.) and Panicum dichotomiflorum Michx., etc in the early June and thereafter it started feeding on paddy crop as soon as it was transplanted (July). During early stages of crop till 39th Standard Meteorological Week (SMW), both adult and grub incidence were recorded on paddy, which built-up during the season. Adults remained associated with the crop till its maturity. The population reached its peak during 31-39 SMW (August-September). Relative humidity significantly and positively influenced its build-up. Natural parasitization of grubs (or pupae) by a eulophid wasp, Chrysonotomyia sp. was reported. Damage and losses inflicted to paddy due to rice hispa as quantified by release density and phenological crop stage revealed that release at early stage (20-days after transplanting, DAT) inflicted more