University of Maryland Extension

Odd Time to See Tomatoes with Mites

Dr. Gerald Brust, IPM Vegetable Specialist

July 2013

A couple of weeks ago I reported high mite populations in some high tunnel tomatoes. This was not too surprising as the high tunnel environment can be conducive to mite build ups i.e., a hot dry environment. But in the past 10 days I have found mite problems in several tomato fields in central and southern Maryland, in some cases the mites were defoliating plants. This is odd as it has not been that hot this summer and it certainly has not been dry as most areas of the mid-Atlantic have seen rain events several times a week. Mites usually do not do very well in a wet environment. One thing, most, but not all farms had in common was that they used pyrethroids of some kind several times early in the season to control worms, Colorado potato and flea beetles and thrips. While pyrethroids are valuable control chemicals their use should be limited (but not eliminated) in the early part of the season, because they can flare mites and sometimes thrips (if the thrips have built resistance) later in the season. Pyrethroids are most valuable later in the season when a quick knock-down of a variety of pests is needed in the field.  For pests in the early part of the tomato season, chemicals such as chlorantraniliprole (Coragen), flubendiamide (Belt), or spinetoram (Radiant) can be used for worms; for CPB or flea beetles clothianidin (Belay), dinotefuran (Venom) and for thrips spinetoram or spinosad (Entrust) as well as several neonicotinoids can be used. There are other alternative control chemicals that could be used that can be found in the Commercial Vegetable Production Recommendations. The more we can use chemicals with different modes of action throughout the season the better we will be able to manage insect pests and resistance problems.

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