Efficacy of Different Insecticides and Botanicals Against Greenish Silk-Moth, Trilocha varians (Lepidoptera: Bombycidae) under Laboratory and Greenhouse Conditions

Ficus benjamina, often known as weeping fig, is planted in tropical and subtropical areas and the Greenish silk moth, Trilocha varians has been its major pest since 2019. This newly emerged pest (larvae) of horticultural crops is causing 100% defoliation and even death of plants. A severe attack of this pest has been seen on F. bejamina. The current pest is invading other ornamental plants, especially jackfruit. There was a need to minimize the pest population, but still, no management strategies have been adopted to control this pest in the world. In the current study, the toxicity of three insecticides (belt, runner and radiant), and four plant extracts (Azadirachta indica, Nicotiana tabacum, Moringa oleifera and Eucalyptus globulus) were evaluated against 2nd instar T. varians. Belt was found to be a more toxic insecticide followed by runner and radiant. LC50 of the belt was 25.200, 20.708, 6.374, 2.893, 2.907 and 2.216 ppm after 12, 24, 36, 48, 60 and 72 hours, respectively, while LC90 of the belt was 392.833, 58.822, 148.741, 126.018, 105.504 and 33.039 ppm after 12, 24, 36, 48, 60 and 72 hours of application, respectively under laboratory conditions. The mean larval mortality differed significantly between treatments during the 1st (f = 2.26; df = 3; p = 0.002) and 2nd spray (f = 3.18; df = 3; p = 0.001) under greenhouse conditions. Belt was the most effective insecticide with an LT50 value of 9.749 h (1.865-17.953) followed by runner 11.926 h (5.364–23.813) and radiant 12.857 h (6.516-28.339). Azadirachta indica caused 17.85, 26.79, 37.76, 46.11, 55.77, 71.42 and 88.99% of mortalities at 12, 24, 36, 48, 60, 72 and 96 h of post-treatment, respectively. Probit analysis showed A. indica, N. tabacum, M. oleifera and E. globulus as effective botanicals with LT50 values of 119.761 h (99.443–148.015), 128.175 h (102.091–148.531), 151.681 h (144.347–189.368) and 157.182 h (149.331–201.152), respectively. The leaf damage by larvae differed significantly between both insecticide and botanical treatments in all rounds of spraying. The current findings could assist farmers in mitigating this pest and aid policymakers in developing Integrated Pest Management (IPM) strategies. Our results are particularly valuable for screening effective insecticides, contributing to the overall management of this pest.