Identification and confirmation of hotspot areas and management ofroot (wilt) disease in coconut

Abstract

Phytoplasma malady associated with root (wilt) disease in coconut is a serious threat and causes heavy economic loss to the coconut farmers in Kerala and Tamil Nadu in India. A roving survey was carried out during 2016–2019 to assess the disease incidence in Coimbatore, Tirupur, Dindigul, Theni, Tenkasi, Tirunelveli and Kanyakumai districts. From the results, Cumbum block in Theni district, Tenkasi block in Tirunelveli (Tenkasi) district and Kuruthancode block in Kanyakumari district were identified as hot spot area for root (wilt) incidence. The disease is generally recognized based on leaf symptoms, but the development of foliar symptoms in coconut palms is very slow and there is a time lag between infection and symptom expression. To the confirmation of the latent infection of root (wilt) affected palms, Direct Antigen Coated (DAC) indirect ELISA has been standardized earlier. Since this ELISA system requires 24 hours, a modified protocol was developed using leaf disc as test antigen that was simple, rapid and provide results within 7 hours. The test yielded 98% more sensitivity with respect to the visual observations. The modified protocol is used for the routine screening of coconut palms for selection of disease-free mother palms and for developing root (wilt) resistant varieties. Besides this, the test is used for confirmation of root (wilt) disease in the early stages of the infection and in newly affected areas. The result of the field experiment on root (wilt) management revealed that the soil application of microbial consortia (Trichoderma viride (Tv)+ Pseudomonas fluorescens (Pfi)+ Bacillus. subtilis) at 100 + FYM 5 kg + phosphobacteria at 200 g at quarterly intervals along with copper sulphate at the concentration of 75 g at three months intervals was effective in reducing the disease incidence from 13.33 to 8.13% after two years of treatment.