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Blister beetles

Blister beetles are long, slender, three-fourths inch long beetles; either gray, black, or striped in color. They feed on leaves and flowers.

Blister beetles are an occasional, isolated problem. Some species produce the toxin cantharidin, an irritant that can cause blisters on internal and external body tissues. The toxin, not beetle feeding, is extremely significant because it causes sickness in livestock and can even kill them. Even if beetles are killed, the problem may not be solved. Cantharidin remains in the bodies of dead beetles and can still cause injury if baled with the hay. There are very few reported fatalities in cattle and sheep, but contaminated hay can be deadly to horses (cantharidin from only a few dead beetles can kill a horse). Therefore do not sell blister beetle infested hay to horse owners.

Females deposit from 50 to several hundred eggs in the soil crevices. After hatching, larvae feed on grasshopper and cricket eggs. Adults fly into fields, where they feed on foliage. The beetles are usually found in late spring and summer. Blister beetles are often worse in fields adjacent to weedy grassy areas that contain an abundance of grasshopper eggs (Crop Science OSU). One thing that I have found to work on most garden pests is real easy to make at home, and it may help with deer. I found that mixing 5 cloves of garlic, 4 tablespoons of red pepper flakes, 1/4 cup of dish soap and 2 gallons of water in a garden sprayer work quite well. I use all natural dish soap which is detergent free and organic garlic and red pepper flakes. I have not used this on any tomato plants. I have a certified organic farm and there for I am very cautious about what goes into and onto my produce. The only real draw back to this is that you have to wash all produce, no more walking threw the garden and grabbing a piece of lettuce or green bean.

Blister beetles (Epicauta vittata and other closely related species) appear in swarms in summer, just as tomatoes, beans and other crops start looking good. This native species does one service � the larvae eat grasshopper eggs � but then the adults strip leaves from a dozen different plants. Hand-picking them can be dangerous, because a toxin in the beetles� bodies can irritate the skin. Blister beetles often drop to the ground and play dead when disturbed, so the best way to collect them is to quietly sneak up and shake them into a pan of soapy water placed beneath the plants. Wear gloves to pick up any stragglers.

Some gardeners grow calendulas as a trap crop, or you can skip over a few pigweeds (Amaranthus species) when weeding and let them serve as blister beetle magnets. Old-time gardeners used pine branches to sweep the beetles into water-filled pits. If all else fails, spray infested plants with Monterey Garden Insect Spray, which contains spinosad, a biological pesticide made by fermenting a naturally occurring soil-borne bacterium.

Organic Control: Hand pick but wear gloves to prevent blisters.

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