Tomatoes—the mere mention of this luscious red fruit can make many people’s mouths water, unless you use the words “blister beetle” in the same sentence. One of the most common of the tomato plants’ many invaders, the blister beetle is a striped gray or black insect (usually about ½ inch long) that often attacks the plants in swarms, consuming the green foliage in massive amounts. Failing to be prepared for a blister beetle infestation can leave you with a crop of pillaged tomato plants. Check your tomato plants daily for early signs of blister beetles so you can control the problem before it gets out of hand.
Identify early signs of blister beetle damage on your tomato plants. According to the University of Illinois Cooperative Extension, blister beetles are chewing insects that attack your tomato plants by chewing holes in the foliage. Look for small holes on your tomato leaves. This pest typically travels in groups, so you should also be able to find the insect itself fairly easily.
Isolate infested tomato plants. Check any surrounding tomato plants to identify those that are infected, looking for the bugs themselves, as well as signs of any leaf damage. If your tomato plants are in movable containers, remove the infected tomato plants immediately so the blister beetles can’t get to your other tomatoes.
Remove the blister beetles from your tomato plants by hand. Don rubber gloves before touching the beetles, since their bodies secrete a chemical (called cantharadin) that can cause blisters if they touch your bare skin. This toxin also burns and wilts the foliage on your tomato plants after the insects have begun consuming the greenery.
Drown the blister beetles in a nearby bucket of water so you don’t have to risk damaging your skin by crushing them. Avoid using alcohol to drown them since the toxic cantharadin actually dissolves in the alcohol itself, which can then cause blisters on your skin if your skin comes in contact with it, according to Texas A&M University Cooperative Extension.
Apply an insecticide to kill any remaining blister beetles. Avoid the temptation to wait before using an insecticide. These insects act so quickly when consuming your tomato plants that the sooner you use an insecticide, the quicker you can save your plants. According to Oklahoma State University Cooperative Extension, approved insecticides you can use to kill blister beetles include Sevin and Thiodin. Organic options include natural chemicals such as pyrethrum and rotenone, according to the National Sustainable Agriculture Information Center. Follow the product directions carefully to ensure that you kill all remaining blister beetles.
Continue to check your plants daily throughout the rest of the growing season for signs of blister beetles. Treat your tomato plants with insecticide when necessary.