Seasonal incidence of insect-pests affecting Aonla (Emblica officinalis Gaertn.) in relation to abiotic factors

Abstract

The observations were recorded at Sardarkrushinagar, Gujarat during 2021 at fortnightly intervals in field from 1st Standard Meteorological Week (SMW) to 52nd SMW. The damage due to Betousa stylophora Swinhoe ranged between 0.80 and 48.8 percent with its peak (48.8% twig damage) in the 35th SMW, while the leaflet damage due to leaf rolling caterpillar ranged between 0.11 and 12.48 percent and exhibited its peak (12.48%) during the 31st SMW. In the case of bark eating caterpillar, the infestation ranged between 2.00 and 10.00 percent branch damage and reached its peak level (10.00%) during 26th SMW. Commencement of aphid appearance was recorded from 15th SMW with 0.02 aphid index, which reached its first peak (2.78 index) during 24thSMW and second peak (1.12 index) during 31st SMW. Physical factors viz. minimum temperature (MinT), morning relative humidity (RH1), evening relative humidity (RH2), rainfall (RF) and bright sunshine (BSS) established significant correlation with ‘r’ value of 0.521**, 0.578**, 0.887**, 0.605** and -0.665**, respectively with gall forming black caterpillar. The infestation of leaf rolling caterpillar established significant correlation with MinT (r= 0.592**), RH1 (r= 0.636**), RH2 (r= 0.883**), wind speed (WS) (r= 0.395**), RF (r= 0.521**) and BSS (r= -0.770**). The activity of bark eating caterpillar established significant positive correlation with physical factors viz., MinT (r= 0.436*), RH2 (r= 0.404*) and WS (r= 0.663**) whereas, aphid showed positive association with MinT (r= 0.588*), RH1 (r= 0.424*), RH2 (r= 0.385*) and WS (r= 0.824**). Key words- Aonla, Betousa stylophora,Cerciaphis emblica,Gracillaria acidula, Inderbela tetraonis,, Insects, Seasonal incidence