Host-plant acceptance on mineral soil and humus by the pine weevil Hylobius abietis (L.)

1 The pine weevil Hylobius abietis (L.) (Coleoptera, Curculionidae) is an economically important pest of conifer forest regeneration in Europe and Asia. 2 Soil scarification, which usually exposes mineral soil, is widely used to protect seedlings from weevil attack. However, the mechanism behind this protective effect is not yet fully understood. 3 Field experiments were conducted to determine the pine weevil's responses to visual and odour stimuli from seedlings when moving on mineral soil and on undisturbed humus surface. 4 One experiment measured the number of pine weevils approaching seedlings, with and without added host odour, on mineral soil and undisturbed humus. Seedlings with added host odour attracted more weevils on both soil types. Unexpectedly, somewhat more weevils approached seedlings surrounded by mineral soil. 5 In a similar experiment, feeding attacks on seedlings planted directly in the soil were recorded. Only half as many seedlings were attacked on mineral soil as on undisturbed humus. 6 In the first experiment, the weevils were trapped 2.5 cm from the bases of the seedlings' stems, whereas they could reach the seedlings in the experiment where seedlings were planted directly in the soil. We conclude that the pine weevils' decision on whether or not to feed on a seedling is strongly influenced by the surrounding soil type and that this decision is taken in the close vicinity of the seedling. The presence of pure mineral soil around the seedling strongly reduces the likelihood that an approaching pine weevil will feed on it

Feeding behaviour of the black pine beetle, Hylastes ater (Coleoptera: Scolytidae)

1 The feeding behaviour of Hylastes ater was investigated at 15 °C and 20 °C on a range of tree species. The role of an aggregation pheromone and the part played by olfactory cues in food selection was also investigated. 2 A distinct hierarchical preference at both 15 °C and 20 °C such that Pinus radiata > Pinus sylvestris > > Picea abies > > Rubus fruticosus=Betula pendula was shown. 3 Feeding on P. sylvestris led to the highest weight gain, closely followed by P. radiata and P. abies. Slightly elevated feeding was observed at 20 °C compared with 15 °C. 4 Reduced feeding in the presence of B. pendula suggests the possibility of an antifeedant effect and predamaged wood was found to be less nutritious, possibly due to greater plant defences. 5 The role of an aggregation pheromone was not supported. Olfactory cues enabled the detection of woody hosts, although differentiation between host was not observed. 6 These results are likely to be important in helping to design an effective integrated control approach against this pest