Factors affecting the attractiveness of foliage for oviposition by Cardiaspina albitextura.

Abstract

Field observations and experiments show that, when Eucalyptus blakelyi is heavily infested by Cardiaspina albitextura, the attractiveness of leaves for oviposition is affected greatly by the psyllid itself. It appears that the attractiveness of leaves depends not only on such factors as leaf age and position on the growing shoot but also on the quantity of favourable food available in them. Heavy feeding either by nymphal or adult psyllids greatly reduces the attractiveness of leaves as oviposition sites. On the other hand, the presence of eggs increases the attractiveness of leaves in proportion to the number laid on them. At times of very high psyllid abundance, the majority of eggs are laid on part only of the small quantity of foliage which escapes severe damage by the nymphal stage. The contagious distribution of eggs laid on such foliage is probably due largely to the increased attractiveness of some leaves as oviposition sites, owing to the presence of eggs, and to the reduced attractiveness of others resulting from heavy feeding by adult psyllids.