Occurrence of insect pests of sugarcane and their natural enemies in relation with weather parameters and effect on cane quality

摘要

Field studies were conducted with one cane cultivar in Punjab, India to monitor the incidence of key insect pests and their natural enemies in Sugarcane. The incidence of early shoot borer was 2.96% and cumulative incidence of top borer was 13.20%. Stalk borer infestation at harvest was 9.62%. Over the period 2006-09, Pyrilla perpusilla incidence was low (0.33 insects per leaf) while Aleurolobus barodensis incidence varied from nil to traces. Isotima javensis, Rhaconotus scirpophagae and Stenobracon sp. were recorded as major parasitoids of top borer larvae and pupae from March to September in each season/year. While Cotesia flavipes was recorded as major parasitoid of stalk borer in all the years under study. Top borer had positive correlation with weather parameters such as maximum, minimum temperature, relative humidity and rainfall. Early shoot borer numberswere positively correlated with maximum and minimum temperatures but negatively correlated with relative humidity and rainfall. Stalk borer incidence was negatively correlated with maximum temperature, minimum temperature and rainfall but positively correlated with relative humidity. I. javensis, S. sp. and R. scirpophagae numbers/populations were positively correlated with the maximum and minimum temperature during the period of this study years. Four cane cultivars viz. CoS 8436, CoJ 83, CoJ 89003 and CoJ 88 were used to study the effect of insect damage on sugarcane quality. Cane quality parameters viz. pol% juice, purity and CCS% decreased due to the damage by these insect pests.