Sunday, August 16, 2009

Spider Mites are not considered to be a serious threat to modern day soybean production but when they do appear they can cause their fair share of yield reduction. So when you see them be prepared to control them.They will always start at the field edge like the above photo shows and then work their way on into the field.You will recognize them by how they stunt and lighten up the crops colour.Notice how the soybeans are a lighter green in the foreground of the field shot below.Don't be surprised if you feel itchy after walking through a soybean field infected with spider mites.They will cause you to feel that way.Spider mites can infest corn as well but it is far more rare than soybeans and it will generally only happen under the severest of droughty conditions.
You can detect their presence by taking a severely stippled soybean leaflet like the one below and firmly shaking it against a blank white sheet of paper.Spider mites will be just barely visible to the naked eye.They are .5-1.00 mm in length rounded, eight legged and yellowish brown with two dark spots on the sides of their abdomen.
When you tap a leaf like the one shown here against a white sheet of paper don't be surprised if you see hundreds of small microscopic round bodies moving on the paper.These will be spider mites.Though they are small they can cause a great deal of damage.In fact when left uncontrolled in a hot dry year they can kill an entire field of soybeans.
Notice the reddish bronzing on the underside of this leaf.Careful inspection with a magnifying lens will show that there is a lot of cobwebbing already present and a high pressure of spider mites evident.Here's a magnified lens shot of what a spider mite looks like.
Once the wheat crop matures or wheat harvest is completed spider mites will begin their move into green lush soybean fields like that shown above.Two Spotted Spider mites will generally only infest soybean fields when grassy borders or adjacent fieldcrops have dried up from heat and drought stress.They move in from the field edge much like that shown in the photo below.Their early dectection is key to curbing their activity.A field perimeter spray application of Cygon,laygon or Matador can stop their further movement.
Spider mites feed on the underside of the soybean leaf.Their feeding will cause leaves to first start showing a stippling appearance and then eventually curl and bronze.

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