Preliminary study on host selection of Pyemotes zhonghuajia
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Key Words:Pyemotes zhonghuajia, Semanotus bifasciatus, Adosomus sp., host selectivity, instar
Abstract:Pyemotes zhonghuajia Yu, Zhang & He is one of several species of recently discovered natural parasites which have been broadly applied in biological control of forest wood borers in China, such as Buprestidae, Cerambycidae and Scolytidae. In order to determine the host preference of P. zhonghuajia, experiments were conducted indoors using a specially constructed sixarmed frame. Two species of pest larvae, Semanotus bifasciatus (Motschulsky) and Adosomus sp. were used to assess host species and host instar selection by the parasite. It was found that female adult mites displayed signficant orientation towards first instar larvae of S. bifasciatus, Within 8 h, the number of female adult mites choosing 1stinstar larvae was significantly higher than those choosing 3rdinstar larvae. After 12-24 h, the number of female adult mites choosing 2nd and 3rd instar larvae increased. Differential selection of 2nd instar larvae of the two host species was also observed. The mites showed a significant preference for S. bifasciatus over Adosomus sp. during an 8~12 hour period in the sixarmed frame. After 24-36 h the mites inclined towards the larvae of Adosomus sp., showing a significant difference at 48 h. It is concluded that P. zhonghuajia shows obvious selective preferences for host species, as well as for specific instars of that host, but that these differences change significantly with time. The mite prefers early instar larvae when their skins are soft and hosts which display low activity.