Pigeonpea is an important food legume crop in semi-arid tropical and sub-tropical farming systems. Pigeonpea is drought-tolerant leguminous crop representing about five percent of world legume production. Among various constraints for low productivity of pigeonpea, infestation of the insect pests and loss caused by them is main contributory factors. Although biopesticides still represent a very small portion of plant protection at present, but their role is significant from future aspects point of view as they provide environment friendly alternative to chemical insecticides. With this view, the present study was planned to understand the relationship between pest incidence and natural enemies of pigeonpea with weather parameters.
It concluded that incidence of the four pod borers (Helicoverpa armigera, E. atomosa, M. obtuse and M. vitrata) and the damage to the pigeonpea pods caused by them had positive relationship with maximum temperature (Tmax). Whereas, the minimum temperature (Tmin) showed negative correlation with average larval population of these pod borers as well as the pod damage caused by them. The correlation between larval incidence and percent pod damage of H. armigera, E. atomosa, M. obtuse and pod damage due to M. vitrata showed positive correlation with morning relative humidity (RH I). Moreover, the rainfall had negative correlation with all the pod borer complex infestation, while sunshine hours had positive correlation with all the pod borer pests in respect of their larval population as well as pod damage in pigeonpea.
Correlation between occurrence of natural enemies and weather parameters indicated that maximum temperature (Tmax) and morning relative humidity (RH I) had significant positive correlation with coccinellid, chrysopid and spider population but the morning relative humidity (RH I) showed positive correlation with coccinellids. Also, sunshine (hrs) had positive correlation with the occurrence of coccinellids, chrysopid and spiders in pigeonpea crop. Whereas, minimum temperature (Tmin), evening relative humidity (RH II) and rainfall exhibited significant negative impact on the occurrence of natural enemies viz., coccinellids, chrysopid and spiders in the pigeonpea field.
International Journal of Statistics and Applied Mathematics
