Mites and Thrips

IPM Threshold Guide for Agronomic Field Crops

Cyclamen mites have been found in a few Mary-land strawberry fields in the last few weeks. They are not much of a problem now but when we start to warm up, they may become more of a problem along with two spotted spider mites.

Spinach Crown Mites in Spinach

Broad mites Polyphagotarsonemus latus have been found in a couple of raspberry fields in Maryland in the last week or so. Most fields had light to moderate infestations of broad mites. The problem is recognizing whether or not you have broad mites because they are so small, they are very difficult to find even with a 10x hand lens and their feeding can look very similar to the damage caused by some environmental problems or by viruses (which are usually the causes of the damage symptoms).

Bulb mites (usually Rhizoglyphus spp) are a problem of garlic that easily go unrecognized. Usually growers notice a general yellowing of their garlic plants with the tips of leaves often turning brown (fig 1). If you examine the bulb it can have feeding marks on the outside of the bulb (fig. 2) or the basal plate can separate easily from the bulb (fig. 3).

With the cooler weather we have had of late I was surprised to find low levels of mites in strawberry fields, with a few hot spots of mites in some high tunnels. There were two species of mites found: the two spotted spider mite, Tetranychus urticae and the cyclamen mite Phytonemus pallidus.

I visited some strawberry fields over the last few weeks in Maryland and while most of the fields were on plastic, some were matted row production. Overall I found low levels of mites in most of the fields, with a few hot spots.

With the majority of freezing night time lows behind us, strawberry growers should begin scouting for pests during bloom. Earliglow is already in bloom on the Lower Eastern Shore and other cultivars will soon follow with the warm weather forecasted for 4/12-4/16. Be on the watch for spring pests during bloom including thrips, tar-nished plant bug, leafrollers, aphids, leafhoppers which begin attack plants during flowering in Maryland. Author: Haley Sater; Title: Spring Pest Scouting in Strawberries

About two weeks ago I heard some reports of possible damage caused by broad mites Polyphagotarsonemus latus in caneberries in the mid-Atlantic region. So I ventured out and looked at several raspberry and blackberry growing operations in Maryland. I found one farm with a light to moderate infestation of broad mites in their raspberries. This operation was relatively small consisting of a little more than a ¼ acre or so of caneberries.

I have seen several sweet corn fields lately that have sulfur deficiencies (fig 1). One of the possible reasons we are seeing more S deficiency is because less sulfur is being deposited into the soil from the atmosphere due to reductions in acid rain. In 1986 about 24 lbs/a of sulfate were deposited in Maryland soils per year, however in 2011 it was closer to just 8 lbs/a each year. Organic matter supplies most of the sulfur to the crop, but sulfur must be mineralized to sulfate-S to be taken up by crop plants.