Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2001
Publication Date: 3/1/2002
Citation: Day, W. H. 2002. The biology, host preferences, and abundance of Mesochorus curvulus (Hym: Ichneumonidae), a hyperparasite of Peristenus spp. (Hym: Braconidae) parasitizing plant bugs (Miridae: Hemiptera) in alfalfa-grass forage crops. Annals of the Entomological Society of America. 95(2):218-222 Interpretive Summary: Plant bugs (family Miridae) are moderate to serious pests of many crops across the U.S., damaging fruit (strawberries, peaches, apples, etc.), vegetables (beans, cauliflower, celery, etc.), fiber crops (cotton), crops grown for seed, and reforestation seedlings. The USDA-ARS laboratory at Newark, DE has established two European parasites to reduce plant bug numbers. Fewer plant bugs will eliminate or reduce crop damage, which benefits farmers because less or no insecticide use is required (reducing production costs), and crop quality is higher (because some damage occurs even with insecticides). Our initial research showed that the introduced parasites were themselves attacked by MESOCHORUS, a hyperparasite (parasite of a parasite) that was already present in the U.S. However, the present study showed that parasite losses to the hyperparasite were low (1 to 11%) over a ten-year period, and were not sufficient to significantly reduce the eeffectiveness of the USDA biological control project. This research also provided much-needed basic biological information on MESOCHORUS.
Technical Abstract: MESOCHORUS CURVULUS was the only secondary parasite (hyperparasite) reared from six primary parasites (Braconidae: 5 PERISTENUS spp., 1 LEIOPHRON SP.) collected in the field, in their mirid hosts. These six braconids parasitized nymphs of four species of phytophagous plant bugs, two (LEPTOPTERNA, TRIGONOTYLUS) feeding on forage grasses, and two (ADELPHOCORIS, LYGUS) feeding on alfalfa. The principal samples were collected weekly and biweekly on commercial farms in northwestern New Jersey, over a ten year period. Although M. CURVULUS attacked six primary parasite species, it preferred PERISTENUS PALLIPES, which in turn preferred the two non-native, grass-feeding mirids. These preferences suggest that both P. PALLIPES and M. CURVULUS are also not native to North America. Rates of hyperparasitism were higher in the most abundant primary parasites, so were density-dependent. The low hyperparasitism rates observed (1 to 11%) indicate that MESOCHORUS does not have a strong negative effect on the primary parasites, several of which are useful in biological control of plant pests. Diapause in MESOCHORUS appears to be regulated by the primary parasite, rather than by photoperiod. The sex ratio of M. CURVULUS was normal (55% female).