Field evaluation of fungal pathogens and plant extracts against arecanut root grub, Leucopholis lepidophora Blanchard.

Field evaluation of bioagents and plant products was carried out for three consecutive years during 2006–08 against root grub, Leucopholis lepidophora Blanchard at Sirsi, Karnataka, India. The results revealed that, chlorpyriphos 20 EC at the rate of 6 ml per palm was highly effective treatment with 77.36 per cent mortality of grubs and was significantly superior over all other treatments. The next best treatment was phorate 10G at the rate of 25 g per palm with 68.13 per cent mortality of grubs. Among the plant products, aqueous mixture of soapnut and neem oil at the rate of 10 percent emerged as next best treatment with 53.71 per cent mortality and was on par with its lower dosage i.e., aqueous mixture of soapnut and neem oil (5%) with 49.93 per cent mortality. The results of the large scale trials conducted over two locations during 2009 revealed that, the eco-friendly treatment viz., aqueous mixture of soapnut and neem oil at the rate of (5%) recorded 53.55 per cent mortality as compared with the best chemical treatment viz., chlorpyriphos 20 EC at the rate of 6 ml per palm (63.95% mortality). Thus, this botanical could be used in field to combat the pest and it will be effective up to 60 days. Among the two mycopathogens under study at two different dosages, Metarhizium anisopliae with 2 x 10⁸ conidia per g at the rate of 20 g per palm recorded the mortality (31.38%) similar to that of aqueous strychnine seed extract at the rate of 5 percent (31.64%). As there is a overlapping of generations in field, it is advisable to incorporate the fungus culture with the onset of monsoon, when beetles emerge in large numbers and lay eggs.