By Christian Krupke, Extension Entomologist
It’s not every week that a new active ingredient is approved for use in field crops, so this is worth a newsletter entry — abamection is an effective miticide and has been for many years in a variety of specialty crops, including apples and other tree fruits.
Effective against a variety of mite species, this should prove a welcome addition to the pest management toolbox for soybean producers during mite outbreaks.
In the past, we’ve had to cobble together a management program with select pyrethroids and Lorsban (chlorpyrifos), and although this approach can work it's far from optimal and carries some hazards that include flaring mites. So this announcement is good news, because we will see mite problems again at some point, it’s just a question of “when.”
This year has not been a “mitey” summer so far — in general, crops are healthy and well-hydrated. A couple of weeks of high temps and no rain could change that so a review of mite i.d. and scouting is a good idea. Remember that a stressed soybean plant is one that is primed for mite infestation. Mites are always present, unnoticed, along field edges in grass/clover etc., and stressed soybeans along field edges will show damage first.
Foliage damage from spider mite feeding is expressed initially as subtle stippling or “sand-blasted” appearance, which may progress to a bronzing and necrosis should dry conditions persist and mites left unchecked. Bronzed foliage is irreversible, meaning the damage is done at that point.
Before considering control, it is very important that spider mites are identified as the source of yellowish or bronzed plants in a field. Many readers are familiar with the process from 2012, when mites were a problem in many, if not most, soybean fields in the state. There are many other diseases, pathogens and nutrient deficiencies that can cause similar appearance in foliage.
To confirm the presence of mites, shake some discolored soybean leaves over a white piece of paper. Watch for small dark specks moving about on the paper. Also look for very tiny, fine webbing on the undersides of the discolored leaves.
Once spider mites have been positively identified in the damaged areas of the field, it is essential that the portions of the entire field be scouted to determine the range of infestation – spider mites are very patchy in colonizing fields and are often restricted to borders – meaning there is no need to treat the whole field.