The effect of European red mite, Panonychus ulmi, on chlorophyll content and chlorophyll a/b ratios of apple, malus domestica borkh., leaves in a growth chamber study (acarina: tetranychidae)

Abstract

The effect of European red mite feeding on the total chlorophyll content and the chlorophyll a/b ratios on 5 selections of apple were determined using potted grafts. The study was conducted in a growth chamber with initial infestation levels of 0, 30, 60 or 120 mites/graft, respectively. Significant differences (P< .05) were found among selections in the number of mites following infestation. Selection 2175-7 supported the fewest and selection 1769-3 had the most mites. In the presence of mites leaf chlorophyll content decreased with time and total chlorophyl content was inversely related to the chlorophyll a/b ratios. Pre-infestation chlorophyll values were not significantly different among selections, but they were lower (P< .05) after the 28th day of infestation and thereafter when mites were present. A recovery of leaf chlorophyll content after the removal of mites was not evident. The results suggested that chlorophyll changes due to European red mite feeding were different between resistant and susceptible selections, due possible to differences in the levels of feeding.