| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The utilisation of aphid-attacking aphelinid parasitoids indigenous to Japan was assessed as biological control agents against Aphis gossypii and Myzus persicae, pest aphids of horticultural crops in glasshouse. As parasitoids of these aphids were confirmed four species of Aphelinus, of which Aphelinus gossypii and Aphelinus sp. B (nr.varipes) are important. The mean developmental period (*) in 15L-9D was 21.9 days at 18ﾟC and 12.3 days 25ﾟC in Aphelinus gossypii, and 23.3 days at 18ﾟC and 13.7 days at 25ﾟC in Aphelinus sp.B.The mean total numbers of eggs deposited per female and the mean total numbers of aphids killed by host feeding in 15L-9D were, respectively, 57 and 11 in Aphelinus gossypii at 18ﾟC,and 48 and 24 in Aphelinus sp.B at 25ﾟC.Aphelinus gossypii accepted both Aphis gossypii and Myzus persicae as hosts, but the latter was inferior in suitability to the former. Aphelinus sp.B readily oviposited and developed successfully to adulthood not only in these two aphids but also in Aphis craccivora, which is useful for mass production of the parasitoid. Aphelinus sp.B showed geographical variation in the ability to enter diapause in response to short photoperiod : Hokkaido and Kyoto populations diapaused at 10L-14D,18ﾟC,but Okinawa population did not diapause. The effects of three insecticides (malathion, pirimicarb and fenvalerate) on Aphelinus gossypii were tested in the laboratory condition. LD50 values were greater when applied directly to adult parasitoids than when applied to mummified aphids (including parasitoid pupae) : 16-fold in malathion, 38-fold in pirimicarb and 6-fold in fenvalerate. Compared to LD50 values of susceptible and resistant clones of Aphis gossypii, pirimicarb seemed to have minimal adverse effects on this parasitoid among these three insecticides.
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