Screening of germplasms and population dynamics of major insect pests of spring green gram Vigna radiata (Linn.)
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Date
2021-09
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation was conducted during Spring season of 2021-22 at Norman. E. Borlaug. Crop Research Centre of G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand) and Morphology laboratory of Department of Entomology with the objectives screening of germplasms of green gram in field as well as laboratory conditions, occurence major insect pests in field conditions. Major insect pests observed in green gram during spring season were whitefly, Bemisia tabaci (Gennadius), thrips, Megalurothrips distalis (L.), jassids Empoasca kerri (Pruthi) and tur pod bug Clavigralla gibbosa (L.). The population dynamics indicated that incidence of Bemisia tabaci and Empoasca kerri were recorded during the vegetative stage and attained their peak population at 17th SMW, while infestation of Megalurothrips distalis was recorded during flowering stage attaining the peak at 19th SMW and highest population of Clavigralla gibbosa was seen during pod formation stage reaching peak insect population at 19th SMW. Correlation studies indicated that max and min temperature, max RH and sunshine hours showed significant positive correlation with whitefly population whereas, thrips population showed significant positive correlation with max temperature, min temperature and max RH. Jassid population showed significant positive correlation with max temperature, min RH. In regression analysis coefficient of determination varied from 0.96 to 0.99 and the percent eigen values of principle component 1 was 4.76 whereas eigen values of principle component 2 was 1.27. Screening of seventy green gram germplasms under field conditions indicated that twenty germplasms were found promising having lower mean population of insect pest. Among the twenty germplasms four (SSME 21-70, SSME 21-55, SSME 21-47, SSME 21-41) showed less preference to S. litura as compared to check PM-05. The four less preferred germplasms were checked to see the effect of trichome density and length on tobacco caterpillar feeding. It was seen that length and density of trichomes varied significantly among the germplasms and proved that the most tolerant germplasm (SSME 21-70) having more trichome density (215.6e) followed by SSME 21-55 (194.6d) as compared to PM-05 (118.3 a) whereas, maximum length of trichomes were seen in SSME 21-70 (1357d) followed by SSME 21-55 (1186.3c) as compared to PM-05 (918a) which indicated that higher trichome length and density contributed to less preference to insect feeding.