Twospotted Spider Mite on Marigold in the Greenhouse, 1996

In late May 1996, 108, 6-inch-tall marigolds were planted in 6 inch pots at the Pesticide Research Center, Michigan State University. The plants were infested with twospotted spider mites, raised on bean plants in the laboratory, by placing 3 infested leaves on each test plant. Pretreatment counts were made on 13 Jun by collecting 4 leaves from each plant and counting the number of mites on the underside of each leaf with a dissecting microscope. The plants were then blocked by the pretreatment counts. All treatments were sprayed on 19 Jun with an R&D CO2 sprayer with an 8008 flat fan nozzle at 50 psi to first runoff. Each treatment was replicated 6 times with each replicate being an individual plant. Reps 1-3 were of the variety ‘Orange Boy’ and reps 4-6 were of the variety ‘Little Devil Yellow’. Post-treatment counts were made on 21 Jun, 25 Jun, 1 Jul and 9 Jul in the same manner as the pretreatment counts.