Onion Thrips Control, 1989

Abstract

Onions were direct seeded at approximately 15/row ft on 20 Apr at Keilen Farms, Inc., Lansing, MI. Plots were 2 rows wide (6 inch double rows), 30 inch spacing between double rows, 25 ft long, arranged in a randomized complete block design with 4 replications. One double row was left unsprayed between each plot. Treatments were applied with a hand-held COa sprayer, 2 nozzle boom (1 nozzle/row), at 40 psi and 30 gpa. On 1 Jun, malathion (1.25 lb (AI)/acre) was applied by air. Treatments were applied 9, 17, and 25 Aug. On 20 Jul a pre-spray sampling of 10 samples (20 plants/sample) was conducted, leaf bases of the pulled plants were rinsed with 70% ethanol. The rinsate (with thrips) was collected in a cup and returned to the lab. Samples were filtered through a Buchner funnel onto filter paper, and the number of thrips counted under the binocular microscope (120 x). On 3 Aug a second pre-spray sampling of 16 samples (20 plants/sample) was done. On 14, 23 and 31 Aug, 20 plants/plot were randomly selected. Numbers of thrips collected from each plot for all of the post-spray samples were summed to estimate season long impact.