Temperature, Location Key To Predicting Leaffooted Bug Pressure
May 26, 2016 This year, leaffooted bugs are expected to be a significant problem in almonds and pistachios, but watching temperature and the insect’s favorite overwintering homes can help growers predict what they might expect in future years.
Kris Tollerup, University of California Cooperative Extension integrated pest management advisor based at the Kearney Agricultural Research and Extension Center, says last fall and winter’s temperatures didn’t get low enough for long enough to kill off many of the leaffooted bug populations.
The insect feeds on young almond nuts before shells harden, causing the embryos to wither and abort. Even after shell hardening, leaffooted bug can cause black spots or wrinkled and misshapen nut meats.
Similar damage can occur in pistachios.
“The pistachio shell hasn’t lignified, and it’s still penetrable. There’s basically nothing in the pistachio at this point,” Tollerup says. “But they will find it, poke into it, feed a little and destroy it.”
The pests overwinter primarily in pomegranates, though they can be found in palm fronds and pump houses, as well as some citrus crops.
“In a mild winter, they’ll make it, and in the spring, and especially in these warm springs like we’ve had the last couple of years, they’ll start to move out,” Tollerup says.
The key temperature, he’s finding, is 27°F. If the leaffooted bugs experience that temperature for a few hours at a time over the winter, they’re unlikely to survive in large numbers. Tollerup’s lab research using cold cabinets shows that about 75% of the insects succumbed to the cold after six hours at or below that temperature.
Growers and pest managers can scout by standing with their backs to the sun and using a long pole to tap upper branches of trees to get the leaffooted bugs to fly out.
“These things are big. If they fly, then you can see them,” Tollerup says.
Finding one over 20 minutes or so might not require treatment. But five or more during an orchard check would be a concern. Tollerup suggests being judicious as broad-spectrum insecticides are the only really effective control method, and they can be harmful to beneficial insects also present.
More on the leaffooted bug, as well as suggestions for control methods, can be found at the University of California Statewide Integrated Pest Management Program website.
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