Onion thrips management: Section 18 exemption for Movento
The Section 18 exemption for Movento is available in Michigan and onion growers can use this product for onion thrip management in 2013.
The Section 18 exemption for Movento (spirotetramat), used for onion thrips management in Michigan, has a minimum interval between applications of seven days, a pre-harvest interval of also seven days and the maximum amount of Movento that can be applied in a single growing season is 10 fl oz/acre, with 5 fl oz/acre as the only approved rate of application.
According to the Section 18 label, two applications of Movento can be made to onions within a growing season, and these should be done consecutively, seven to 10 days apart, for insecticide resistance management purposes. Movento has to be tank-mixed with a non-ionic (penetrating) surfactant to maximize leaf uptake since this product moves systemically in the plants. This means that tank-mixing Movento with fungicides that have spreader-stickers can reduce efficacy of this insecticide. For example, Chloronil tank-mixed with Movento reduces thrips control, but Dithane F45 Rainshield, Rovral 4F, Scala SC and Quadris F tank-mixed with Movento doesn’t impact onion thrips control negatively.
Movento is more effective at suppressing larval onion thrips, therefore Michigan State University Extension recommends that it’s used in the early part of the growing season, before thrips population pressure peaks. The MSU Vegetable Entomology Lab recommends that the first Movento application in the growing season is made when thrips pressure reaches the one thrips per leaf stage in the growing season.
To scout for onion thrips, visually survey onions and count the number of thrips and the number of leaves per plant. Check 10 plants per location and check at least five different locations spread throughout the onion field to get an average for onion thrips and leaf numbers per plant. Divide the average number of onion thrips per plant with the average number of leaves per plant to calculate the average thrips per leaf. For example, if you find that on average you have three thrips per plant and that plant on average has three leaves, then you have reached the one thrips per leaf threshold, and an application is warranted.
For more information, please visit the MSU Vegetable Entomology lab website.
Dr. Szendrei’s work is funded in part by MSU’s AgBioResearch.