Mites and Thrips

There have been problems in our vegetable fields with three pests, which include striped cucumber beetles, leafhoppers and twospotted spider mites. I think most of the problems we are having with these three comes from our mild winter as each has had an outbreak population after a mild winter sometime in the last 12 years.

I visited some strawberry fields over the last few days in Maryland. Most of the strawberry fields were on plastic but some were matted row production and a few in high tunnels. With the cooler weather we have had of late I was surprised to still find low levels of mites in the fields, with a few hot spots of mites in some high tunnels. There was only one species of mite found: the two spotted spider mite, Tetranychus urticae.

Insect Pest Management in Peppers

Insect Pests of Tomato

High tunnels (HTs) are up and running now and we usually do not see many pest problems early on, but there are some potential problems that could develop later in the season that get their start now. One potential problem is when the HT was not cleaned up after the previous year’s crop was finished. Many of these are old tomato plantings, most of which had their plastic, stakes and drip-tape removed but the plants were left to rot in the HT over the winter.

It is unusual that I see or hear about broad mites (Polyphagotarsonemus latus) being a problem in our tomato high tunnels. A grower was having symptoms of twisted growth and browning/bronzing of their tomato leaves this spring and guessed they might have broad mites. They did, with some plants severely damaged while others were fine. The grower had a late fall crop of cherry tomatoes that they kept into December but did not clean up their high tunnel until 2 weeks before they planted their spring crop of tomatoes. Unfortunately, the grower had a small infestation of broad mites in the fall crop of tomatoes that was able to overwinter.

The hotter temperatures we have had have caused thrips and to a lesser extent two spotted spider mite, TSSM (Tetranychus urticae) populations to rapidly increase in some vegetable fields. These pests feed by puncturing the outer layer of plant tissue and sucking out the cell contents, which results in stippling, discolored flecking, or silvering of the leaf surface (fig.1).

Over the past few weeks we have seen several greenhouse (GH) and high tunnel (HT) vegetable (basil and tomato mostly, but also lettuce, pepper and spinach) operations from around Maryland having problems with thrips.

Cyclamen mites have been found in a few mid-Atlantic strawberry fields as well as more widespread to the south of us in North Carolina. So once we start to really warm up they may become more of a problem along with two spotted spider mites.

In the past, field trials I have conducted on gold flecking were inconclusive as to its causes as they showed more problems caused by environmental concerns than by thrips or mites. However, upon several visits to growers’ fields over the last 4 years that were having mite or thrips outbreaks there were almost always greater rates of gold flecking in the most heavily infested areas of the tomato field.