In vitro comparative toxicity of chemical insecticides and botanicals against ladybird beetle (Micraspis discolor F.) in Nepal

Micraspis discolor F. is the most abundant ladybird beetle in rice crop ecosystems and an effective natural predator of several economically significant agricultural pests. However, the widespread use of non-selective insecticides has disrupted natural enemy populations, highlighting the need for safer alternatives to integrate into pest management strategies. Limited research exists on the toxicity of commercial and bio-rational insecticides on beneficial insects. Therefore, this study aimed to evaluate the toxicity of various insecticides and botanicals in a laboratory setting to determine which pesticide is safest for M. discolor and to assess its mortality. The experiment followed a completely randomized design with five treatments: Azadirachtin 0.03% EC, garlic extract, Dimethoate 30% EC, Chlorpyrifos 50% EC + Cypermethrin 5% EC, and a control, each replicated five times. Mortality rates were recorded at 24, 48, and 72 hours’ post-exposure. The results showed that M. discolor was significantly affected by Chlorpyrifos 50% EC + Cypermethrin 5% EC, which caused the highest mortality (86%) after 72 hours, followed by Dimethoate (74%). Among the tested substances, garlic extract was the safest, with a mortality rate of 54%, although still higher than the control, which exhibited no mortality. These findings highlight the potential of botanical extracts as safer alternatives for pest management, aiding in the conservation of beneficial insect populations. Furthermore, in order to promote sustainable agriculture, future research should concentrate on developing safer substitutes that reduce damage to pollinators, parasitoids, and natural predators while preserving efficient pest control.