Twospotted Spider Mite Control on Greenhouse Marigolds, 1992

Selected insecticides were evaluated for control of twospotted spider mites on potted marigolds in a greenhouse. Plants were transplanted from four-inch to one-gal pots 15 May and plants were watered once a day by drip irrigation. Plots consisted of a single, potted plant and treatments were assigned as a CRD with four replications per treatment. Sprays were applied to the point of runoff using a one gal B&G compressed air sprayer with a hollow cone nozzle tip. Insecticide applications were made on 16 and 22 Jun. Control plants received a water spray treatment. Adult and nymphal mites were counted on 6 randomly selected leaves per plant. Leaf size was estimated to the nearest cm2 by comparison with charts of marigold leaves of known area, the number of mites were converted to numbers per cm2 by dividing by leaf size prior to analysis. Visual damage estimates were made on 10 Jul by two observers.