EFFECT OF NEEM KERNEL AQUEOUS EXTRACT (NKAE) ON GROWTH AND DEVELOPMENT OF RED SLUG CATERPILLAR, ETERUSIA MAGNIFICA BUTL IN TEA IN NORTH-EAST INDIA, INDIA

Abstract

ABSTRACT Aqueous extract of neem seed kernel (NKAE) was tested in laboratory conditions to evaluate its effects on larval weight, larval duration, mortality percent, adult emergence percent and antifeedant activity against red slug caterpillar, Eterusia magnifica (Lepidoptera: Zygaenidae).Different concentrations of NKAE as 2,4,6,8 and 10% were used separately to evaluate the effects of NKAE. NKAE was found to be effective and concentration dependant against Eterusia magnifica. Larval weight was concentration dependant and decreased with the increase of NKAE concentrations. Antifeedant activity was in ascending order with increase in concentrations. The highest leaf area consumed were recorded at 2% concentration in fifth instar as 1158.6+254.79 sq cm and it was lowest at 8% concentration in first instar larva as 92.2+26.04 sq cm. The leaf area protection of NKAE was recorded as 48.09+12.61-61.59+11.28% in first, 22.74+13.59-54.31+14.16% in second, 60.05+11.94-87.5+2.98% in third, 33.9+10.79-65.82+15.71% in 4th and 30.32+10.2-64.48+19.35% in 5th instar larva at 2-10% concentrations respectively. Preference index obtained for NKAE in all tested concentrations indicated its deterrence against feeding of red slug caterpillar. The larval duration recorded maximum as 5.8+0.45, 6.6+0.55, 7.6+0.55, 7.6+0.55 and 13.6+2.1 days at 8 percent concentrations over control as 4.4+0.55, 5.4+0.54, 5.6+0.55, 6.6+0.55 and 10.6+1.7 days in 1st, 2nd, 3rd, 4th and 5th instar larva respectively. The larval mortality was maximum after 72 hrs of treatment at all the concentrations and recorded 12.92+0.02-98.23+2.1% in 1st, 9.07+0.4 - 39.4+2.2% in 2nd, 7.53+0.7 – 32.63 +0.8% in 3rd and 2.59+1.0 – 11.9+0.6% in 4th instar at 2, 4, 6, 8 and 10 percent concentrations of NKAE respectively. Adult emergence percent was reduced to 0-35.63+1.7 in male and 0-29.4+1.1 percent in female at 8-2 percent concentrations as against 99.1±0.6 and 97.6+0.5 respectively in the untreated control.