News release: Tomato Insects

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640

Release Date: August 4, 2016
Headline: Tomato Insects

In my last column, I discussed the types of diseases which typically plague tomatoes in Missouri, and gave a few examples of each type.  This week, I would like to cover a few of the major insect pests that you will need to keep a lookout for when growing those prize winning tomatoes.

One of the more dramatic insects that attacks tomatoes, at least in terms of visible damage in short order, is the tomato hornworm.  These insects can strip tomato stalks bare of leaves very quickly.  They are also very large in size, up to four inches in length.  Green in color, they can blend right into the foliage and hide easily, in spite of their size.  To control tomato hornworms, you can easily pick them off if there are only a few per plant.  If you have a large infestation or number of plants, you can use insecticides such as Sevin, or a biological control such as Bt.  Be sure to follow all directions and observe pre-harvest intervals when using any agricultural chemical.

A similar insect is the tomato fruitworm, which is also known as the corn earworm.  Yes, the same worm that messes up your perfect ear of sweet corn can also attack your tomatoes.  Be sure to destroy any infected fruit, so that the worm won’t be around to reproduce.  Insecticides are the same as those used for the tomato hornworm.

Yet another type of worm is the cutworm, which can attack tomatoes at any stage of growth, from seedlings to mature plants including tomato fruits.  Sevin can be used to control them.

Several insects attack tomato leaves, leaving them injured or deformed and less able to supply sugars to those growing tomato fruits.  One example is the aphid.  These insects typically curl and deform leaves.  While the damage may not look extensive, there is a problem beyond what you see.  Aphids are known to transmit a number of viral diseases, and once your tomato has a viral disease, it cannot be eliminated.  Other insects that transmit viral diseases include flea beetles, leafhoppers, thrips, and whiteflies.  These should be controlled with an appropriate insecticide.

Two other beetles that can cause problems in tomatoes include the Colorado potato beetle and the blister beetle.  They will eat foliage, and can be controlled with sevin.

Leafminers occasionally attack tomatoes, leaving long, slender tunnels inside the leaves, which are visible and appear as white streaks.  You can also see damage from stink bugs, which suck juices from the fruits and cause hard, cloudy or irregular whitish spots under the surface of the skin. Again, you may need to spray to control these pests.

The final pest that I will mention is actually not an insect at all.  It’s the spider mite, which is microscopic in size, and feeds on leaves.  These pests cause small yellow areas in the leaf.  Their populations can expand rapidly under hot, dry weather.  Control can be achieved using a miticide, or if you spray diligently, an insecticidal soap.