Holy Guacamole! Tiny Bug Threatens U.S. Avocado Supply
California’s epic drought isn’t the only thing putting a chip in your guacamole dip supply. Now a tiny but deadly beetle looms as another big threat in a state that grows 95 percent of the United States’ avocados.
Farmers already had been abandoning their groves in San Diego County—the nation’s avocado capital—as water rates soared. For those still in business, a mysterious new pest that recently began attacking a range of trees seems to have a particular affinity for avocados.
“We’ve found that the beetle is drawn to 138 tree species, and it attacks 13 agricultural crops, but it can only reproduce on avocado trees,” said Akif Eskalen, a plant pathologist with the University of California, Riverside. “Why, we don’t know.”
That has the California Avocado Commission worried. The trade group has given $800,000 to Eskalen and other researchers to figure out how to stop the polyphagous shot hole borer.
The beetle is no bigger than a sesame seed, but the damage it can wreak is huge. And scary.
It’s so new to the U.S. that entomologists at first struggled to identify it. But what really worries them is that the beetle seems to target perfectly healthy trees, not sick ones, and it doesn’t leave the tree until it’s completely destroyed.
“This is the first time we’ve found it in such a large scale in Southern California, in commercial groves,” Eskalen said.
About 40 percent of California’s avocado crop is grown in San Diego County, according to the California Avocado Commission.
“We don’t know what kind of damage it can do, how soon it will kill the plant, or how it spreads,” Eskalen said. “We’re also trying to find out how we can control it.” Related Kiss Your Guacamole Good-Bye: Drought-Stricken California Farmers Stop Growing Avocados
Avocado trees on about 1,000 acres in San Diego have been infected in just a few months. That represents 5 percent of the county’s avocado groves. Researchers expect those trees to die, based on what happened in Israel when the beetle invaded groves in that country.
The tiny creature is a crafty enemy.
True to its name, the shot borer drills tunnels deep into the heart of the host tree and sows fungus spores as it travels. The beetle feeds on the fungus, which ultimately kills the tree. Because the pest hides inside the tree, it has proved largely impervious to pesticides.
The beetle was first found in an avocado tree in a residential backyard, prompting efforts to educate homeowners about the invasion to stem its spread.
“Homeowners may not know to identify the beetle. They may cut it down and dump the tree someplace, and the beetle can spread that way,” said Timothy Spann, a plant biologist and the California Avocado Commission’s research program director. “So part of our effort is educating the landscaping industry, the nursery men and other stakeholders, to make sure it doesn’t spread because of human action.”