The Plumas-Sierra Agricultural Department has confirmed the presence of blister beetles in Sierra Valley, marking the first confirmed sighting in the area. The identification was made by the California Department of Food and Agriculture (CDFA) Plant Pest Diagnostics Center, which analyzed multiple insect samples submitted by concerned Sierra Valley residents.
The identified blister beetle species is about ½ inch long, with a narrow and elongated body and soft, flexible wing covers. Other variations of blister beetles, including gray or striped, are also known to exist, often characterized by yellow, orange, and black stripes.
Blister beetles feed on grasshopper egg pods and the eggs of ground-nesting bees. They also consume alfalfa, clover, and other flowering plants found in native hay meadows and pastures. In the absence of blooms, these beetles resort to feeding on leaves.
While typically not a major problem in California, blister beetles pose a significant threat due to their secretion of a toxin. The toxin can cause blisters on the skin and be lethal to livestock. To reduce livestock mortality check hay before feeding to livestock and reduce the incidence of blister beetles in hay by cutting before peak bloom
The toxicity levels of blister beetles vary across species. In some cases, as few as 30 beetles can be lethal to an adult horse, while other species require over 1,000 beetles to reach lethal toxicity levels. Given the unknown toxicity levels, caution is advised.
UC Cooperative Extension Weed Ecology and Cropping Systems Advisor stated some insecticides are registered and may be effective for blister beetle control, however, considering the crop’s growth stage when the application would need to be made and the required pre-harvest intervals for various products, there are pros and cons to making an application. Cutting the field before the beetles start to move into the field before bloom may be the most economical option.”
For further information or questions, contact Tom Getts with UCCE at (530) 251-2601 or Willo Vieira at the Plumas Sierra Agricultural Commissioner’s office at (530) 283-6365.
