Management of Yellow Vein Mosaic Disease of Okra and Study of Virus-vector Relationship Thesis

Abstract

Okra (Abelmoschus esculentus L.) is an important vegetable crop belongs to family Malvaceae. India is the largest producer of okra in the world with total area of 0.52 million hectares and production of 6.26 million tonnes green pods, whereas productivity of the crop is 12.1 mt/ ha (Anonymous, 2012). Yellow Vein Mosaic (YVM) is the most important and destructive disease of okra and is a major constraint in okra production. The present investigations were carried out on "Management of yellow vein mosaic disease of okra and study of virus-vector relationship " during 2014-15. In pot experiments different level of vectors (whitefly) such as 1, 5, 9, 12, 15 and 20 were used to study the transmission of OYVMV. The single viruliferous white fly transmitted minimum (18.75% and 15.38%) disease in first and second experiment respectively, whereas maximum transmission (100%) was found with 20 viruliferous whiteflies which significantly increased transmission of OYVMV on test plant. The highest transmission percentage of OYVMV (75 .00% and 76.96%) was found to be with 6 hrs acquisition feeding period on test plants in first and second experiment respectively. The lowest transmission percentage of OYVMV was recorded with 15 minutes acquisition feeding period. The highest susceptibility to virus was recorded (100%) in the 15 and 20 days old plants in both experiments and remaining plants were also found susceptible to OYVMV. In another experiment, the effect ofplant leaf extracts (2.0%), bio agent (1.0%) and chemicals (0.1%) .were found to be effective for reducing whiteflies population. The maximum number of decrease in whiteflies population were recorded after 7 and 14 days of spray using combination of Azadirachtin 0.03% + Imidacloprid 70 WG + Beuveria bassiana (5.33 and 5.67) and (3.67 and 4.00) in both experiments. The minimum number of whitefly decrease by Bhang extract (11.33 and 11.67) and (8.33 and 8.67) in both experiments, whereas untreated control was recorded with (17.00 and 18.00) white fly at 7 and 14 days after first spray and (18.67 and19.33) white fly at 7 and 14 days after second spray