The effects of infection on level of the twospotted spider mite, Tetranychus urticae Koch, on injury and, contents of chlorophyll and inorganic substances in apple leaves
1988
Lee, S.W. | Lee, M.H. (Rural Development Administration, Suwon (Korea R.). Agricultural Sciences Inst.) | Shin, K.C. (Rural Development Administration, Suwon (Korea R.). Horticultural Experiment Station) | Hyun, J.S. (Seoul National Univ., Suwon (Korea R.). Coll. of Agriculture)
Studies were conducted to investigate the effects of infection level of the twospotted spider mite, Tetranychus urticae, populatio2048ns on visual leaf injury and contents of chlorophyll and inorganic substances in apple leaves of the young apple trees. Visual leaf injuries over 50 % leaf areas occurred when the population densities were maintained at about 10 adult females per leaf for several days. Many of the injured leaves at late June dropped from late July to August. Therefore, it seems that early season infestation causes severe reductions in total number of leaves at much lower population. Chlorophyll contents were reduced in proportion to the degree of visual leaf injury. The concentrations of nitrogen, potassium, and calcium were significantly reduced at high injury levels. No reduction in phosphorus concentration was observed at any injury level. On the other hand, magnesium concentration was increased at high injury le
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