The occurrence of leafminers and their parasitoids on vegetables and weeds in Hangzhou area, Southeast China

Leafminers are the most important insect pests of vegetables in Hangzhou area, Zhejiang province, Southeast China as well as in the rest of China, but have never been investigated for species composition, relative abundance and their associated parasitoids. A survey was conducted in four localities of Hangzhou area during 1998-2000 to determine the distribution of leafminers and their parasitoids on vegetable crops and weeds in the field. Over 20,000 leafminers were collected and reared. The leafminer species found were Liriomyza sativae, L. chinensis and Chromatomyia horticola, with C. horticola and L. sativae the most abundant in spring and autumn, respectively. About 11,000 parasitoid adults were reared from the leafminers collected. In total 14 hymenopteran species of four families (one braconid, 10 eulophids, one megaspilid and one pteromalid) were found. Eleven species were reared from C. horticola, nine from L. sativae and seven from L. chinensis. Opius caricivorae and Chrysocharis pentheus were the dominant species. Seven species were recorded from L. chinensis for the first time. Eleven parasitoid species were reared from leafminers on two weeds (Veronica undulata and Sonchus oleraceus). Parasitoids caused 48.5-68.8% parasitism on leafminers on crops and 83.7% parasitism on leafminers on weeds in the later growing season of vegetable crops. The results suggest that leafminer populations are regulated to a certain extent by their natural enemies in the field.