Thrips Insecticide Rotation Recommendations Available

Published: December 31, 2016

Some growers in the central part of Missouri have noted difficulty in controlling thrips on tomatoes the last couple of years, both field and in tunnels. Dry bulb onions have gained in popularity by many growers as well. While onions have always been noted as being plagued by thrips, tomatoes do not have thrips listed as a pest in the 2017 Midwest Vegetable Production Guide for Commercial Growers. We expect thrips to be added as a tomato pest to the 2018 edition of the guide. The 2017 edition of the guide expanded its insect control section to provide both an action threshold, and a recommended insecticide rotation. Note the example below which was developed for onion.

Example of Insecticide Rotation for Onion Thrips Management
The table below provides an example of an insecticide rotation growers can use to manage onion thrips in dry bulb onion. It provides thresholds for use with each product. Note: Only apply Exirel® a maximum of two back-to-back applications during the season.

Growers could use this rotation for other crops, such as tomatoes in the field or a tunnel. When growers struggle with thrips control, it is often because they get established on the tomatoes early. Use of sticky cards can be helpful to notice an emerging population. Then be conscientious about regular applications of pesticides while the plants are smaller or when thrips pressure is high. Thrips often develop on onion sets and move to tomatoes, or move to tomatoes from adjoining fields, such as when hay is cut. Therefore, isolating tomato plants from crops known to harbor thrips (e.g. onion) is an important part of thrips management.

It is worth noting that two of the products in the above rotation are relatively new: Movento and Exirel. Both are in chemical classes not used much, IRAC #23 and 28, respectively. Use of Agri-Mek (IRAC #6) for thrips control may not be familiar to many growers, as it is more known for spider mite control. If a grower expects problems with thrips, obtaining products such as Exirel, Movento and Radiant (IRAC #5) ahead of time may be worthwhile, since they are not as readily available as other pesticides. Unfortunately, none of these products is recommended for stink bug control. Additionally, the guide’s revised thrips control section for onions notes several pyrethroid products (e.g., Ambush, Pounce & Warrior II) have lost effectiveness against thrips due to the development of resistant populations.