Lettuce was a leaf vegetable with short growing term and cold-tolerant plant. We grew it the whole year. The price of lettuce is the most expensive from July to September. But damages by lots of insect pests appear to greenhouse grown lettuce in summer season. In this study, we observed biological controls of western flower thrips(Franklinella occidentalisi) by the predator mites, Amblyseius swirskii and Neoseiulus cucumeris in lettuce greenhouse from July 7 to September 10. Hypoaspis aculerfer larvae and adults were released 30 individuals per m2 at the first one time as lettuce was planted on the greenhouse. We checked the density of F. occidentalis every 10 days on the 30 lettuce leaves. When the population of F. occidentalis reached 1~5 individuals per a leaf, A. swirskii larvae and adults were released 35 individuals per m2 at 1~3 times and Neoseiulus cucumeris larvae and adults also were released 150 individuals per m2 at 2~3 times in each lettuce greenhouse. During the high temperature season, Amblyseius swirskii was more effective biological controls of F. occidentalis than Neoseiulus cucumeris.

When paprika is cultivated during summer season, thrips starts to occur in the early growing season and reaches its peak in late June. In the treatment using Orius laevigatus and Neoseiulus cucumeris, natural enemies to thrips, thrips density was 87.6/trap and 51.31trap on June 23. After Orius laevigatus and Neoseiulus cucumeris were treated twice on June 24 and July 23, the number decreased considerably. On August 23, it was 36.9/trap and 40.3/trap and from the mid August to early September thrips density remained low. Effect of Orius laevigatus and Neoseiulus cucumeris on suppression of thrips density was 35.7% and 44.6% on July 22, however, the number went up to 88.8% and 80.5% on September 3.