|TWOSPOTTED SPIDER MITES|
|Effects of Spider Mite¹ Injury on
Transpiration and Leaf Water Status in Peppermint²
JACK D. DE ANGELIS, K. C. LARSON, RALPH E. BERRY, AND G. W. KRANTZ
Department of Entomology, Oregon State University, Corvallis, Oregon 97331
© 1982 Entomological Society of America
Environ. Entomol. 11: 975-978 (1982)
Studies were conducted to examine effects of feeding injury by the spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), on diurnal transpiration and daytime leaf water status in peppermint, Mentha piperita L. A new approach to investigate mite injury of the leaf epidermis and cuticle is presented. Feeding injury significantly affected daytime stomatal transpiration and nighttime cuticular transpiration. High rates of nighttime transpiration that resulted from mite injury to leaf epidermal cells and overlying cuticle caused leaf water stress during the day. Differences in rates of transpiration during the day and night, between uninjured and injured leaves, were correlated with a leaf injury index developed for this study. Water stress (more negative leaf osmotic potential) developed in injured leaves during the day and the magnitude of stress was correlated with our leaf injury index. Continued water loss at night from miteinjured leaves is discussed in terms of the underlying cause of water stress during the day.