Influence of feeding on foliage of previously defoliated Scots pine upon subsequent development and fecundity of Diprion pini L. (Hymenoptera, Diprionidae)
1990
Geri, C. (Institut National de la Recherche Agronomique, Ardon (France). Centre de Recherches Forestieres. Station de Zoologie Forestiere) | Goussard, F. | Levieux, J.
Experiments were carried out in 1985, 1988 and 1989 to show the influence of the consumption of previously defoliated Scots pine foliage on Diprion pini. Studied trees have been defoliated by the insect itself. In standard laboratory conditions (20 degrees C, 16 h/8 h photoperiod) groups constituted by 40 or 50 Diprion larvae were fed from the 4th instar to cocoon spinning, using foliage of defoliated pines or foliage of undefoliated pines. In the first experiments, pines were neighbouring trees of the same age and of the same nursery. In the following experiments, defoliated and control pines belonged to the same clone. Defoliation during the previous year proved to reduce significantly fecundity. Insect weight was also reduced and change in diapause rate may be observed. Insect survival is unaffected. Recent defoliations does not harm D. pini. In both cases no decrease of development rate is observed. Conversely larval development may be accelerated. Induction of fecundity decrease by defoliation appears to play a part in population dynamics of D. pini
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