Tuesday, July 18, 2017

Could Two-spotted Spider Mites be Lurking in your Soybean Field?

Spiders. These creepy crawlers makes a lot of peoples skin crawl with discomfort, but how would you feel if you had to deal with spider mites? Occasionally, we can have a problem of two-spotted spider mites.  They are very, tiny greenish-yellow arachnids, overwinter as adults, and then lay eggs in the spring. The hatching mites establish colonies on the undersides of leaves and produce webbing over the leaf surface, prompting the name “spider” mites. 

Spider mites occur during periods of hot weather and drought, when there is low humidity.  Their symptoms can range from silvering, yellowing, browning, lower leaf loss and death, or could possibly be mistaken for drought symptoms.

Drought is a big contender in outbreaks of mites, along with natural enemies, weather, and host quality. This is because drought will enhance the spider mites acceleration of reproduction as well as  movement to a crop from surrounding vegetation as it improves food quality for mites.  Since fungal diseases flourish in wet, cool conditions, drought diminishes the diseases that normally attack spider mites. 

Now let’s get to the important stuff, scouting! The best time to scout for spider mites is during times of hot and dry weather.  The first place you should look for mites are in areas where soybeans are stressed.  If you are in an area where the leaves looked sandblasted, take a clipboard with a white piece of paper and tap the leaves on it. After you tap the leaves and there appears to be yellow, brown, or black speckles on the white paper, you probably have found some mites! Crush the speckles on the paper and if they appear to be a reddish-brown spots, then you have spider mites. 

There have not been thresholds established for two spotted spidermites in soybean as of yet, but we do know that we need to protect the canopy during the most critical growth stages during pod and seed development.  Since these pests are "mites", not all insecticides will kill them, so be sure to apply a miticide only in severe infestations. 

(Maggie Prather, Burrus Agronomy Intern and Stephanie Porter, Burrus Sales Agronomist)

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