Biochemical responses of cucumber to Tetranychus urticae Koch (Acari: Tetranychidae) mediated biotic stress

The effect of two spotted spider mite (Tetranychus urticae Koch) feeding on leaf level physiological characteristics of cucumber (Cucumis sativus Linnaeus) was investigated. Young cucumber plants were artificially infested with different densities of T. urticae (5, 10, 15 and 20 mites/ grown up leaf) while uninfested plants acted as control. Post infestation, the plants differed in their support to mite density in accordance with initial infestation density and observation period. Highly significant negative correlation of -0.92, -0.93, -0.95 and -0.92 for total chlorophyll, chlorophyll a, chlorophyll b and carotenoids, respectively, at the highest infestation level) was recorded between mite density and photosynthetic pigments in infested leaves as compared to uninfested ones. There was a significant decrease (P= 0.05) in the level of (a progressive decline from 2.82, 0.36 and 2.17% dry weight in control to the maximum of 2.09, 0.26 and 1.87% dry weight for N, P and K, respectively, at highest infestation level) in the infested leaves in response to mite infestation. Interaction between initial infestation level and observation period also suggested a significant impact of T. urticae infestation on the leaf phytochemicals of cucumber (P= 0.05)