Development of a system for sampling population levels of subterranean Eriosoma lanigerum (Homoptera: Aphididae) in apple orchards
Sampling systems for population studies of subterranean woolly apple aphid, Eriosoma lanigerum (Hausmann) (Homoptera: Aphididae), are not available. Therefore, a system for monitoring underground population levels of this species was developed. A standard soil sample was taken to a depth of 15 cm using an auger with an internal diameter of 5 cm. Either a hand or mechanical auger may be used. Distance from the trunks of apple trees, and the amount and nature of root material in the samples, affected the number of aphids recorded. More aphids were recorded in soil samples containing root material, particularly if the roots had galls resulting from the feeding of E. lanigerum, than in samples in which there were no roots. The number of E. lanigerum in samples decreased as the distance from the trunk at which they were taken increased. The distance from the trunk at which samples were taken was standardized to 30 cm. The system will be suitable for detecting changes in subterranean population levels over time and for comparing soil treatments for woolly apple aphid control, but not for decision making regarding the necessity for control actions.