SEASONAL INCIDENCE, YIELD LOSSES AND FIELD EFFICACY OF INSECTICIDES AGAINST SUCKING PESTS OF SUMMER GROUNDNUT 2520
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Date
2018-03
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JAU,JUNAGADH
Abstract
Experiments were conducted on “Seasonal incidence, yield losses and field efficacy of insecticides against sucking pests of summer groundnut’’ at Instructional Farm, College of Agriculture, Junagadh Agricultural University, Junagadh during summer, 2016.
Studies on seasonal incidence of the major sucking pests of groundnut, variety TG-37, revealed that the aphid population initiated from the 1st week after sowing i.e. the fourth week of February with 0.48 nymph/ 3 leaves/ plant. The population of the pest increased gradually from the 1st to 7th week after sowing and reached the peak population (5.44 nymphs/ 3 leaves/ plant) in the 7th week after sowing coinciding with the 2nd week of April. However the second peak of population (4.64 nymphs/ 3 leaves/ plant) was observed in the 8th WAS i.e. the 3rd week of April. Aphid population was found to occur throughout the crop period. The population declined gradually towards the end of the crop period and remained at zero level at the time of harvest i.e. the 13th week after sowing. The correlation matrix indicated that the population of aphids exhibited significant positive correlation with maximum temperature, mean bright sunshine hours and significant negative correlation with morning relative humidity and wind velosity.
The population of whitefly (0.00 whiteflies/ 3 leaves/ plant) appeared from the 1st WAS i.e. the fourth week of February and start to emergence remained active throughout
the crop period. The pest population increased gradually and reached the first peak level of 4.56 whiteflies/ 3 leaves/ plant during the 8th WAS coinciding with the second week of April. Later on, it was found to decline drastically (0.12 whiteflies/ 3 leaves/ plant) at the time of harvest of groundnut. Correlation coefficient values stated that the population of whitefly exhibited positive correlation with maximum temperature, and bright sunshine hours.
The results indicated that the population of thrips (1.12 thrips/ 3 leaves/ plant) appeared from the 1st WAS i.e. the 4th week of February and remained active throughout the flowering period. The pest population increased gradually and reached a peak level (8.24 thrips/ 3 leaves/ plant) during the 8th WAS coinciding with the second week of March. The population declined gradually during the successive weeks and reached zero level at the time of harvest of groundnut. The correlation coefficient values indicated that the population of thrips exhibited positive correlation with maximum temperature, bright sunshine hours and significant negative correlation with morning relative humidity.
Significantly higher yield of 1600 kg/ ha was recorded from the plots protected against the sucking pests of groundnut, while yield of 1240 kg/ ha was recorded from the unprotected plots. The increase in yield in protected plots over unprotected plots was found to be 360 kg/ ha. This showed 22.60 per cent increase in yield and 29.03 per cent avoidable loss.
The results from the two sprays on aphids have revealed that flonicamid 0.015 per cent, imidacloprid 0.005 per cent, dinotefuran 0.0010 per cent and thiamethoxam 0.01 per cent were found to be the most effective insecticides.
The results of relative efficacy of eleven different insecticides revealed that flonicamid 0.015 per cent and acetamiprid 0.008 per cent gave very good results against the whiteflies.
In accordance with the results obtained from two sprays, spinosad 0.015 per cent and fipronil 0.01 per cent were the most effective of the insecticides against thrips population.
Flonicamid 0.015 per cent recorded the highest yield (1742 kg/ha) and highest cost benefit ratio (1:84.32) was also obtained from the treatment of dimethoate 0.03 per cent.
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ENTOMOLOGY