Watch for mites in this dry weather
At least one soybean field in the Jackson Purchase area has suffered from mite damage. The weather that we are now experiencing is what I would expect for mites to become a problem. There is no guarantee that mites will be a problem in any particular field, but dry (low humidity) weather and drought stressed plants increase the probability of a problem occurring. If you are in an area that has had sufficient rainfall you can probably ignore this warning.
Mites will infest both corn and soybeans but in Kentucky the latter is more likely to result in an economic problem. Double crop beans could be at a greater risk than full season beans just because they are in a “younger” plant stage at the time of infestation.
The most common mite problem in Kentucky grain crops is the two spotted spider mite (Figure 1.). This is a tiny yellowish - redish pest. The mature females have two, well developed, black spots located on either side of their body. These are not insects but eight legged relatives.
In soybeans, the most important infestation window is the reproductive stages of R1 (beginning bloom) - R5 (beginning seed) and it is even more likely in fields where a synthetic pyrethroid insecticide has been used. In our current corn production situation, it may very well be too late to worry about mites. Certainly no control is warranted after the dent stage. In either case, one of the first and most important questions is: am I likely to be able to make a crop?
To sample in soybeans, shake plants over a piece of white paper and look for tiny, moving specks. You will need a hand lens to determine if the specks are actually mites, but if they are crawling across the paper you probably know the answer. In corn, scouting is much more difficult and less is known about making a control decision. The mites are no harder to find, simply follow the instructions for soybeans but use corn leaves. One simply wishes to determine if the infestation is only on the outer edges or occurs across the field. You will need to sample several areas of the field. Mites are notorious for being spotty in their distribution. They also have a very strong “edge effect” which would include waterways, etc. that may cross the field. If a treatable infestation is found, it may very well be controlled by a border application.
Deciding on the need for mite control is very difficult. Suffice it to say that the field needs to be heavily infested; so mites should not be hard to find. Also, two-spotted spider mite is difficult to control with pesticides, especially if a large population is present before they are detected.
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