Diagnosis of retarded growth in an apple orchard

Abstract

Soil round trees in an Adelaide apple orchard was sampled to assess the concentrations of Pythium spp., Phytophthora spp., stylet-bearing nematodes, soil texture (per cent clay), soil moisture and pH. Correlations between these factors and the size of apple trees (trunk circumference) suggested that parasitic nematodes, Pythium spp. and pH might together be important factors inhibiting tree growth. On the basis of these results, a statement is made on the possible causes of retarded growth in the orchard, and how the problem might be overcome. The main purpose of the work was to devise a simple approach that would enable diagnoses to be made of the causes of retarded growth or poor yield in a crop where several factors seemed to be involved. Such an approach might be useful to extension workers who have to deal with many plant disease problems at the same time.