Methods of Recording Aphid Populations for Use in Research on Potato Virus Diseases

Methods of counting aphids infesting potato crops are reviewed and discussed. The results of an aphid survey in different parts of England during 1946 and of counts at Rothamsted during 1947 are given and used to illustrate methods of expressing the counts; the extent of virus spread in 1946 showed no close correlation with aphid numbers. It is concluded that an estimate of the number of aphids per plant is better for virus disease research than the number per 100 leaves. A method of estimating the number of aphids per plant with tolerable accuracy is described, but it is concluded that for most surveys a method which does not necessitate the counting of the aphids is adequate. Such a method, based on the percentage of leaves infested, is described.