Leafminers in vegetables, ornamental plants and weeds in Indonesia: surveys of host crops, species composition and parasitoids

Extensive surveys of vegetable, ornamental and weedy plant species were con ducted in highland and lowland vegetable production areas in Indonesia with the aim of recording leafminer species present and their associated natura l enemies. The most common dipterous species reared from samples was the pe a leafminer, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). Thi s introduced pest was particularly serious in highland vegetables in Java, Sumatra and South Sulawesi, causing yield losses as high as 60 - 70%. Anoth er alien species, the vegetable leafminer, Liriomyza sativae Blanchard, con tributed to problems in lowland areas on the north coast of West Java, wher e cucumbers were heavily damaged. An Asian leafminer species, Chromatomyia horticola Goureau, was more common in snow peas (Pisum sp.). Intensive samp ling of leafminer-infested leaves from surveyed host plants yielded 11 spec ies of hymenopteran parasitoids: 10 eulophids (Asecodes sp., Chrysocharis s p., Cirrospilus ambiguus (Hansson and LaSalle), Closterocerus sp., Hemiptar senus varicornis (Girault), Neochrysocharis formosa (Westwood), Neochrysoch aris sp., Pnigalio sp., Quadrastichussp., Zagrammosoma sp.) and 1 eucoilid (Gronotoma sp.). The most abundant parasitoid species was H. varicornis. Le vels of parasitism varied among crops and growing seasons, but were usually low, especially on potato (< 3%). Surveys revealed that most farmers (63%) attempted to control leafminers by applying insecticides twice weekly alth ough these applications were neither effective nor economical according to responses of about 72% of the farmers. An integrated pest management approa ch is suggested that emphasizes IPM training for vegetable farmers and incl udes reduction or elimination of broad spectrum chemicals that would advers ely affect parasitoids that may already be present as well as those that ma y be introduced. The initiation of a classical biological control programme is recommended to enhance the limited parasitoid complex present in Indone sia and increase levels of biological control.