Spider mites in soybeans
Don’t spray unless it is needed!
- We have seen some fields that were sprayed early with an insecticide/fungicide tank-mix and those fields have the highest populations of spider mites
- The insecticide killed predatory insects that eat the mites and the fungicide controlled the mite-pathogenic fungi!
Other things to consider:
1) Mites are worse near alfalfa and dry areas, often starting in small border areas and then expanding
a) High temps increase spider mite activity
2) Adult spider mites are very small and have two dark spots on the body
a) Webbing can often be seen on the leaves
b) If you cannot see them on the leaves, shake a plant over a piece of white paper and look for the very small moving mites
3) Spider mite damage first appears as stippling (yellow spotting) on the lower leaves
a) As damage progresses, leaves will become brown or bronze, and damage will progress upwards through the canopy
b) There is currently no good treatment threshold in soybeans, but if stippling reaches mid-canopy, you should probably spray
4) Chlorpyrifos (Lorsban), at 0.75 - 1 pint, has activity on mites (with limited egg activity) and has very little residual
a) Use at least 20 GPA to get good coverage
b) Pyrethroids (with the exception of bifenthrin), will cause spider mite populations to flare
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