The termicidal effects of Chlorpyrifos 48 EC, Endosulfan 35 EC, Dichlorvos 1000 EC and Diazinon 600 EC against termites in South-West Nigeria

Studies were carried out at the Cocoa Research Institute of Nigeria, Ibadan to determine the efficacy of four insecticides (Chlorpyrifos 48 EC, Endosulfan 35 EC, Dichlorvos 1000 EC and Diazinon 600 EC) ontermites (workers and soldier castes). The results showed that for both topical and residual action tests, worker caste mortality rates ranging from 70 to 100% were recorded for Chlorpyrifos, Endosulfan,Dichlorvos and Diazinon at 0.063, 0.125, 0.25 and 0.5% treatment levels within 120 min after exposure (MAE). For the soldier caste, the mortality rate was between 10 and 70% at the same treatment levelswithin the same time interval. However, the insecticide concentrations had very low fumigant action against the termites (workers and soldiers) when exposed to different concentrations of their fumes. There was no mortality recorded in any of the control petridishes. A higher mortality of the soldier caste was recorded for the topical application (10 to 70%) than the residual application, which gave a better kill of the workers caste (90 to 100%) 120 MAE. The high death rate of the workers might be due to the fact that they were generally more active during foraging and thus more susceptible to the effects of theinsecticide either by contact or systemic actions. The fact that the workers have a lower surface area and body weight than the soldiers might have also contributed to their higher vulnerability to theinsecticides. The application of these insecticides at 0.25% active ingredient is adjudged the best due to the high mortality rate achieved. Also the application at 0.25% will help to maintain cost effectiveness ofthese insecticides and minimize environmental pollution, toxicity and phytotoxicity problems associated with pesticides