Evaluation of recent fungicides for the management stem bleeding disease in coconut

Abstract

Stem bleeding disease caused by Thielaviopsis paradoxa is an important disease of coconut in Andhra
Pradesh. Among the chemical fungicides tested in-vitro, the most effective in the order of merit were combi fungicide viz., carbendazim 12% + mancozeb 63% WP showed maximum inhibition of 91.11%,95.19% and 97.41% at 100 ppm, 250 ppm, and 500 ppm respectively. The second best treatment was hexaconazole 5% + validamycin 2.5% SC which showed 89.26, 93.70 and 96.30 followed by Azoxystrobin 11% + Tebuconazole 18.3%SC [77.78%, 77.78 and 88.52% respectively]. Based on the in vitro studies, the best chemical fungicides were forwarded to evaluate under field conditions. The treatments were followed with quarterly schedule for a period of two years to observe its affects on the disease. After 27 months of quarterly treatment with root feeding of hexaconazole 5% + validamycin-2.5% SC @4 ml in 100 ml water + soil drenching (@2ml litre-1 ) 15 litre palm-1 (at quarterly interval) has been recorded 42.00 % reduction over initial followed by the positive check with root feeding with hexaconazole @4 ml in 100 ml of water palm-1) with 36.05 % reduction over initial. The next best treatment was root feeding of hexaconazole + validamycin 4 ml in 100 ml of water palm-1 showed 31.17 % reduction over initial. The treatment with root feeding of azoxystrobin 11% + tebuconazole-18.3% SC @ 4 ml in 100 ml water + soil drenching (@ 2ml litre-1 ) 15 litre palm-1 (at quarterly interval) recorded 24.75 % reduction over initial.