Peddes, Angelo (2017) Ruolo dei parassitoidi autoctoni e di quello esotico introdotto nel controllo biologico del cinipide galligeno del castagno in Sardegna. Doctoral Thesis.
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The Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) (ACGW) is considered as a major pest of Castanea species worldwide. The classical biological control based on the release of the parasitoid Torymus sinensis Kamijo (Hymenoptera, Torymidae) is considered to be the only effective method of controlling D. kuriphilus.
The parasitism rates of native parasitoids species are typically low (2-10%), thus they cannot control chestnut gallwasp keeping its population below an economic threshold.
A multi-year monitoring of exotic and native parasitoids of this pest was carried out in Sardinia by collecting specimens inside the galls. At the same time D. kuriphilus infestation and T. sinensis settlement in some release sites has been monitored.
The data collected clearly indicate that D. kuriphilus is decreasing as demonstrated by the decrease of number of galls, infested shoots and number of cells per gall.
Until 2014, the density of T. sinensis has been extremely low in sites different from those of release reaching levels well below those relative to native parasitoids (between 40 and 50%). However, in two years since then T. sinensis became the dominant species in some sites parasitizing 99% of gall wasp cells.
T. sinensis is well established in all release sites but some differences were in density values between galls collected in spring-summer (diapausing larvae) and emergences from “winter” galls suggesting some mortality of overwintering larvae.
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