Hypsipyla grandella is the most harmful insect pest against Meliaceae, including Cedrela spp. and Swietenia macrophylla, in the tropics of the South American region. Field surveys on damages and bionomics of H. grandella conducted in the Peruvian Amazon area under the Forest Regeneration Experiment Project during the period 1983 to 1987 revealed that the population density of H. grandella increased rapidly in the rainy season, i.e. September or October to May. There were some cases where the damage ratios exceeding 50% had resulted in failures in establishing plantations because of the repeated attacks by high density population of H. grandella. The availability of feed stuffs for this species increased in the rainy season, while decreased in the dry season. The seasonal change of H. grandella density was closely correlated with that of newly sprouted host trees. C. odorata was more susceptible to H. grandella attack than S. macrophylla was. Natural enemies identified were several parasitic wasps, a few predatory wasps, a nematode, ants and fungi. Both wasps may greatly contribute to control H. grandella in nature. Mixed planting with other tree species than Meliaceae was not successful in reducing insect damages in line plantations. Since Hypsipyla adults seem to prefer young plants of the host species, planting in clear cut areas may help them identify their host trees for mating and laying eggs. Therefore, in is not advisable to employ clear cutting of more than 5 m-width or clean weeding in plantation. Planting in a small patch may be worth of testing. Natural regeneration under spot planting with shading by a forest canopy would give some effect on reducing the insect attack, though the tree growth may be reduced.