Phenology of glandular trichomes related to entrapment ofPhytoseiulus persimilisA. -H. in the glasshouse tomato

SUMMARYHigh rates of mortality in populations of the predatory mite Phytoseiulus persimilis on tomato plants in spring and summer are due to entrapment by exudate from trichomes. Trichome phenology under glasshouse conditions was analyzed from March to November; their density, size, and amounts of trichome exudate fluctuated seasonally, increasing gradually in spring and decreasing in the autumn. A growth cabinet at 22°C and 65% r.h. was used to measure the percentage of predators immobilized by trichome exudate within one hour on cut leaflet stalks from glasshouse plants. The rate of immobilization was correlated positively with the difference in temperature between the growth cabinet and the glasshouse when the temperature difference was more than +1 K. Otherwise, entrapment was correlated with trichome size and amount of exudate on stems.