A Mitey Big Disaster

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Often, one of the typical options offered when attempting to control an identified pest, is to simply do nothing!  In this year of extremely hot, dry conditions in NE Ohio, deciding to not do anything about a pest, turned into a disaster.  The pest involved was the two-spotted spider mite, which was happily feeding on tomatoes growing in a high tunnel.

 

two-spotted spider mites, tomato
Stippling on tomato leaves caused by two-spotted spider mites

 

When asked what had happened, the grower said that he saw the tomato leaves were going a little yellow, so he decided to increase the amount of fertilizer that he was applying.  After one week, he then noticed that the bottom sets of leaves on most of the tomatoes were turning brown.  So he decided to apply a fungicide to see if that would help the situation.  Another week later, the situation was rapidly getting worse, so he decided this time to apply an insecticide.

 

feeding damage, spider mites
Bronzing of tomato leaves by high two-spotted spider mite populations

 

Now, insecticides are not effective in controlling mites because mites are not insects, which are characterized by having six legs, instead they are acarids, which are characterized by having eight legs.  In fact, many entomologists say that using an insecticide, in an attempt to control mites, may cause the mite population to explode.  This is due to the impact that the insecticide has upon the predators, by suppressing or outright killing many of them, and all of them were actively munching on those mites.

 

2 spotted spider mites on tomatoes
High tunnel tomatoes showing extreme two-spotted spider mite feeding damage

 

Once the predators were eliminated, the mite population exploded in the high tunnel and most of the tomatoes began to quickly become stippled, then chlorotic, then bronze, and finally the leaves just died!  It was a disaster that could not be remedied at that point.  The take home message from this mitey disaster is to correctly identify the problem first, then decide the best management scheme to handle the problem

 

death of tomato leaves due to mite feeding
Tomatoes leaves killed by high mite populations feeding unchecked