Influence of European Red Mite on Leaf and Whole-canopy Carbon Dioxide Exchange, Yield, Fruit Size, Quality, and Return Cropping in `Starkrimson Delicious' Apple Trees

• Published in: Journal of the American Society for Horticultural Science Vol. 121; no. 5; pp. 954 - 958
• Main Authors: Lakso, A.N, Mattii, G.B, Nyrop, J.P, Denning, S.S
• Format: Journal Article
• Language: English
• Published: 01-09-1996
• ISSN: 0003-1062; 2327-9788
• DOI: 10.21273/jashs.121.5.954

The hypothesis was tested that effects of late-season European Red Mite (ERM) [
Panonychus ulmi
(Koch)] injury on apple (
Malus domestica
Borkh.) fruit development are better explained by carbon physiology than by pest densities. Midseason ERM populations were allowed to develop in mature semi-dwarf `Starkrimson Delicious'/M26 trees with moderately heavy crops, then were controlled with miticides at different mite-day (activity of one mite per leaf for 1 day) levels as estimated by weekly leaf sampling. The range of final mite-days was from 250 to 2100 on individual trees. Seasonal fruit growth patterns were monitored. Diurnal whole-canopy net CO
2
exchange rate (NCER) was measured in eight clear flexible balloon whole-canopy chambers on several dates before and after mite infestations. Mite injury reduced fruit growth rates. Leaf and whole-canopy NCER were reduced similarly. Late season fruit growth and final fruit size were correlated with accumulated mite-days, but were better correlated to whole-canopy NCER per fruit. Fruit firmness, color, soluble solids and starch ratings showed no correlation to mite-days. Number of flower clusters per tree and final fruit per tree the following year were not related to accumulated mite-days, but final fruit per tree the following year were better correlated to whole-canopy NCER per fruit. These results generally supported the hypothesis.