ZYGOGRAMMA BICOLORATA PALLISTER, A POTENTIAL BIOCONTROL AGENT OF PARTHENIUM HYSTEROPHORUS L. AND ITS PREDATORSAND PARASITOID

摘要

The success of any biocontrol agent in a natural system is determined by biotic and abiotic factors over a period of time. Some predators and parasitoids have been reported which may reduce the survival rate of the beetle Zygogramma bicolorata Pallister (Coleoptera-Chrysomelidae). This beetle is a natural biocontrol agent for exotic weed, Parthenium hysterophorus L. The weed is spreading in India like a wild fire in all sort of land available to it A tachinid parasitoid Palexorista sp. (Diptera- Tachinidae) is observed, parasitizing 3rd and 4th stages of the grub and percent of parasiteization varied 2.0 to 9.2% in the field and in lab 55-89 percent. Harpactor manginatus (Heteroptera-Reduviidae), attack grubs and adult beetles both and its percentage of predation is recorded 5 to 25% in field and 55 to 70%. In lab. Another predatory bug Eocanthecona furcellata is also observed feeding on the body content of the grubs as well as adult beetles and the percent of predation for this bug was observed 2to 16% in field and 68 to 76% in laboratory. These, parasitoid and predators decreases the biocontrol efficacy of Z. bicolorata by killing them.