Establishment of pine woolly aphid, Pineus pini (Gmelin) (Adelgidae) on some host trees in Kenya
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The establishment of Pineus pini (Gmel.) on 6 common species of pine in Kenya was examined in the laboratory in relation to possible causes for observed differences in the rates of infestation on different host species in the field. In some circumstances crawlers were positively phototactic, but they did not settle on surfaces exposed to strong light, to which they appeared negatively phototactic, consequently tending to settle in hidden and tight crevices. The undersides of lateral branches which received only moderate light tended to harbour a higher concentration of aphids than the upper surfaces. Possibly positive thigmotaxis and negative phototaxis operated together, tending to bring crawlers into situations satisfying feeding and thigmotactic responses. Pinus halepensis was the most favourable food-plant for rapid build-up of infestation and high adult aphid survival. P. elliottii, P. caribaea var. hondurensis and P. oocarpa were also favourable and are recommended for mass rearing and experiments on resistant traits. P. patula and P. radiata were less favourable.