Abstract
Studies were made on season based incidence, biology, damage assessment, population estimation and management of two lepidopteran lac predators Eublemma amabilis Moore and Pseudohypatopa pulverea Meyr. during 2007 to 2010 cropping seasons. In baishakhi crop, the incidence of both the predators commenced in February with the formation of lac cell and reached peak in May. In kartiki crop, E. amabilis started its appearance in August and showed a sharp rise of population in early September whereas proliferation of P. pulverea was found till harvesting in October. Both the predators oviposited either singly or in batch on or near the lac encrustation with maximum egg deposition in the first two days showing fecundity of 214 and 24 with the hatching success of 94 and 66%, respectively. The creamy white larva of E. amabilis measured 10.70 mm in length and 2.25 mm in breadth whereas larva of P. pulverea was blackish in colour measuring 11.20 mm length and 1.95 mm breadth. The pupa of E. amabilis measured 9.10 and 2.75 mm and P. pulverea 5.00 and 2.10 mm in length and breadth. Male and female moth of E. amabilis measured 7.70 and 8.55 mm in length and 17.60 and 19.75 mm wing span, respectively. The P. pulverea male and female measured 4.75 and 5.40 mm in length and 12.95 and 14.25 mm wing span, respectively. The incubation, larval and pupal period, adult male and female longevity of the predators varied with season with the average of 8.83, 30.70, 14.30, 7.73, 8.30 days respectively for E. amabilis and 8.30, 36.33, 10.17, 7.63 and 8.50 days for P. pulverea. A single larva of E. amabilis destroyed 60-80 immature or 5-10 mature lac cells, in contrast P. pulverea caused destruction of 135-190 immature or 10-30 mature lac cells. Population development of E. amabilis and P. pulverea from 2-8 pairs of individuals in the field ranged 42-208 and 10-49 larval population in baishakhi lac crop and 70-234 and 10-53 in kartiki lac crop respectively. Damage potential of E. amabilis was 2-3 times higher than P. pulverea and their respective yield loss ranged 16.53-64.40% and 4.96-33.40% in kartiki crop and 13.91-57.82% and 4.17-28.17% in baishakhi crop. Population of P. pulverea in storage was 10 times higher than E. amabilis in baishakhi lac stick and 2.5 times higher in kartiki lac stick and it became 60 to 70 times higher in stored scrapped lac of both the crops. Sun drying of scrapped lac for 2, 4 and 6 days and aluminium phosphide as fumigant were found to be highly effective in controlling P. pulverea in storage for a period of 90 days. Sun drying for 2 days followed by use of aluminium phosphide as fumigant reduced 8-10% yield loss of lac in storage. In managing the predators in the field, the suitability of the treatments of chemicals and botanicals could be ranked as 10g/L neem seed kernel extract (NSKE)>ficom 0.05%>ficom 0.02%>1% neem oil>1% mehogoni oil>1% karanja oil> ficom 0.01%. Considering the efficacy against the predators, impact on lac insect, net return and cost benefit ratio, the treatments NSKE @ 10g kernel/litre of water and 0.05% malathion (ficom 57EC) were found to be superior in successful management of lac predators in the field and this could be recommended for commercial production of lac.