Among the major oil palm pest insects in the Cote d'Ivoire,Latoia viridissima Holland [Lepidoptera, Limacodidae] is the most frequently observed defoliator. During a pullulation of this species, a natural epizootic permitted us to demonstrate the occurrence of a small isometric RNA virus of 30nm in diameter. The buoyant density of the virus particles was 1.34. The virus capsid contained 2 major proteins with molecular weights of 30,000 (55%) and 31,000 (20%) and 3 minor proteins. One genome component was detected with molecular weight 2,9×106. Agarose gel diffusion tests showed this virus was distinct from any other described insect Picornavirus. Trials with different doses of viral suspensions were tested on industrial oil palm plantation, allocated byL. viridissima, from ground level, using an automatic air carried sprayer. One week after the treatment, a mortality gradient, increasing from 11 to 61% according to the dose applied, was obtained. Two weeks after the treatment the mortality reached 92% of the larvae in the treated parcels. During the next generation, the number of caterpillars on the same parcel was very low.