|Budget Amount *help
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥1,400,000 (Direct Cost: ¥1,400,000)
Six indigenous aphid-parasitizing aphelinid species, Aphelinus abdominalis, A. gossypii, A. albipodus, A. asychis, A. maculatus and A. varipes were known to parasitize four pest aphids, Aphis gossypii, Myzus persicae, Macrosiphum euphorbiae and Aulacorthum solani. The present study investigated the host range, diapause, long-term cold storage and release of the indigenous Aphelinus species, especially A. asychis and A. albipodus to use them as bio-pesticides.
The host aphids of the six species were listed up from the data from field-collecting specimens and some experiments on host preference in the laboratory. Acyrthosiphon pisum was one of the most suitable alternative hosts for mass production of A. asychis and A. albipodus. Short photoperiod in combination with medium temperature could induce diapause at the last-instar larval stage within the mummy in A. gossypii, A. albipodus and A. varipes, but at the adult stage in A. asychis (all Kyoto populations). A. asychis was different in the rate of diapause according to geographical populations. Among three populations examined the rate of diapause was highest in Kyoto population, and lowered in Kochi population, Kagoshima population in order. At least 6 and 20 weeks storage of non-diapausing and diapausing adults, respectively, of A. asychis could be achieved without significant decrease in survival and post storage reproduction when adults were maintained at 5℃,10L-14D condition from just after emergence.
A. asychis and A. albipodus were released on tomato plants infested by Macrosiphum euphorbiae in three small vinyl houses at Kyoto in the spring of 2003. Both parasitoids succeeded for establishment and multiplication in the vinyl houses, but did not result in reduction of aphid numbers during a three-month period, measured by direct counts and indirect monitoring of sticky traps. Rates of parasitism stayed low throughout the season, less than 40%, resulting in severe damage of the tomato crop.