Effects of foliage quality of different Pinus sylvestris L. clones on Diprion pini L. biology (Hymenoptera, Diprionidae) | [Effet de la qualite des feuilles de differents clones de Pinus sylvestris L sur la biologie de Diprion pini L. (Hymenoptera, Diprionidae)
1999
Pasquier Barre, F. (Institut National de la Recherche Agronomique, Olivet (France). Centre d'Orleans, Station de Zoologie Forestiere) | Auger Rozenberg, M.A.
The sawfly Diprion pini causes significant damage in Europe on Pinus sylvestris. The biological cycle of this pine sawfly demonstrated three different interactions between foliage and life stage: 1/ the females which choose a plant to deposit their eggs; 2/ the eggs which are inside a needle damaged by the females with their ovipositor and 3/ the larvae which eat the foliage. To evaluate the effect of foliage on the 3 life stages, oviposition tests with or without host-choice, feeding bioassays and egg survival tests were simultaneously perfommed. D. pini females were able to deposit their eggs on all the tested clones but demonstrated significant host-choice preference among Scots pine clones. Egg survival differed significantly between the clones. Eggs oviposited on some clones resulted in poor egg hatching. These experiments enabled us to determine P. sylvestris clones favorable and unfavorable to sawfly egg survival. Larval feeding bioassays revealed the importance of foliage quality to survival and development of D. pini larvae and permitted grouping clones into two categories according to their effects on larval survival. Nevertheless, no correlation was found between D. pini oviposition preference, egg survival and larval performance. Some clones were always suitable for the sawfly, others were always unsuitable and most were suitable for some life stages and unsuitable for the others. Consequently the differential response of adults and offspring could be used in P. sylvestris breeding programs to prevent high levels of insect populations
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