Cost-effective onion thrips control program 1: Choose good products, add the right surfactant

Ben Werling<werlingb@msu.edu>, Michigan State University Extension, and Zsofia Szendrei, MSU Extension, Department of Entomology - January 20, 2015

The northeast onion industry has a diverse chemical toolbox and effective surfactants to manage onion thrips.

The Midwest and northeast onion industry now has an excellent toolbox of chemistries with different modes of action that, if used right, could provide durable control of onion thrips into the future. By using the right products with the right surfactants at the right time, you can accomplish this goal while minimizing cost.

The right products

Research over the past decade has identified a short-list of effective insecticides from the many formulations labelled for thrips control in onions, including Radiant, Lannate, Movento and Agri-Mek (Table 1). Importantly, old standbys including Warrior are still labelled, but have been rendered ineffective by resistance in some onion growing regions. Recent work shows that Exirel, an insecticide with a distinct mode of action, can be an effective addition to your insecticide rotation. This means now there are five distinct modes of action which, if used in rotation at the right time, will reduce chances that our industry will face the resistance-related control failures that have occurred in the past.

Table 1. Trade names, active ingredients (a.i.), chemical class and insecticide resistance action code (IRAC) for effective thrips control products.

Product	a.i.	Chemical class	IRAC
Radiant SC	spinetoram	spinosyns	5
Lannate LV	methomyl	carbamates	1A
Agri-Mek SC	abamectin	avermectins	6
Movento	spirotetramat	tetramic acid	23
Exirel	cyantraniliprole	diamides	28

The right surfactants and tank-mix partners

The right surfactant can make the difference between excellent control and economic damage. Past work showed that a non-ionic surfactant applied at 0.5 percent v/v (percent surfactant out of total solution volume) greatly improved Movento’s ability to control thrips. Recent work has shown that a variety of other surfactants can accomplish this task; methlyated spray oils (MSOs), organosilicone, terpene, mineral oil and fatty acid products have proven equally effective in Michigan State University and Cornell University trials (Table 2).

Table 2. Examples of surfactants and rates for use with onion thrips insecticides.

Product	Chemical	Rate
JMS Stylet Oil	mineral oil	1.5% v/v
Purespray Green	mineral oil	1 gal/acre
MSO	methylated spray oil	0.25% v/v
Requiem 75EC	terpene	1 qt/acre
Dyne-Amic	non-ionic surfactant	0.25% v/v
Induce	non-ionic surfactant	0.5% v/v
M-Pede	K-salts of fatty acids	2% v/v
Silwet L-77	organosilocone	0.25% v/v

In addition, research from MSU showed that reducing the rate of organosilicone and MSO surfactants by half from 0.5 percent v/v to 0.25 percent did not compromise control. This means there are a variety of equally effective surfactants you can choose from, which can be used at reduced rates in some cases. As important as your choice of surfactant, research from MSU and Cornell has shown that tank-mixing chlorothalonil-based fungicides with Agri-Mek and Movento reduces their efficacy. However, fungicides such as Dithane, Rovral, Scala and Quadris can be tank-mixed without loss of efficacy.

Choosing the right products and surfactants is your first step towards obtaining effective thrips control. The next step is to make sure you apply them at the right time to ensure efficacy, delay resistance and save money.

Dr. Szendrei’s work is funded in part by MSU’s AgBioResearch.

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