| Abstrakt: |
Adults of Panonychus ulmi (Koch) were placed on the lowest leaf of each plant of 9 selections of ‘Delicious’ apple, Malus sylvestris var. domestica, (Borkh.), from Illinois, Indiana, Michigan, Missouri, and New York grown in pots as bench grafts on seedling rootstock. Variation between mite numbers was not associated with selection. Mean numbers of mites varied widely between each strain of the same selection but the differences were not consistent. Highly significant differences in numbers of leaf hairs were found among strains but there were no significant correlations between mite populations and leaf hair numbers. A significant loss of leaf hairs occurred but the difference between numbers of live and dead mites was relatively constant. The total leaves per plant differed significantly between strains of the same selections. There was no correlation between number of leaves per plant and number of mites. Mite counts, leaf production, and leaf pubescence showed no consistent pattern of variation, but strains from different locations within USA did differ in these factors. |
