The flatheaded borer is a beetle, seen right here within the larval stage, identified for attacking branches and trunks, not fruit, so current discoveries of it in Lake County, California, pears have raised questions. (Courtesy Clebson Gonçalves/College of California Cooperative Extension)
West Coast entomologists are asking pear growers to be looking out for pest harm which may be attributable to confused Pacific flatheaded borers.
Specialists in California have discovered a borer pest attacking pear fruit immediately, inflicting signs that look considerably like sunburn or codling moth harm.
The unusual half? Flatheaded borers, a household of beetles typically discovered within the North American West, are solely identified to assault bushes, typically girdling trunks or branches.
“Proper now, we don’t know precisely what we’re coping with,” mentioned Cindy Kron, North Coast IPM advisor for College of California Agriculture and Pure Assets.
Preliminary DNA testing suggests it might be the Pacific flatheaded borer, native to North America, however researchers are ready for extra conclusive identification.
The issue first surfaced in August final yr in Lake County, north of the San Francisco Bay, when pest management advisor Broc Zoller observed darkish spots on the sunny facet of pears and small entry holes close to the calyx. He lower into one and located an off-white, slender grub, the entrance a part of which was broad and flat, giving the critter its identify. A California Division of Meals and Agriculture entomologist recognized it as a flatheaded borer however not as a specific species.
Zoller discovered the borers in 4 orchards, all natural or with low pesticide use. He has seen flatheaded borers on orchard tree trunks and branches, however not often typically sufficient to matter.
“It’s not one thing we actually fear about,” he mentioned.
Zoller labored with Kron and Clebson Gonçalves, a diversified crop advisor for Lake and Mendocino counties, to concern alerts and conduct grower conferences.
California entomologists are investigating what is perhaps the Pacific flatheaded borer inflicting pear harm considerably related in look to codling moth harm and solar harm. (Courtesy Clebson Gonçalves/College of California Cooperative Extension)
There might have been extra undiagnosed influence — written off as codling moth harm — in North Coast orchards, Kron mentioned. With harvest in full swing, the researchers had no probability for systemized sampling.
In the meantime, Gonçalves despatched specimens to the College of Tennessee, the place researchers discovered their DNA per the Pacific flatheaded borer within the genomic database. Nevertheless, that’s not foolproof, Kron mentioned. Somebody may have made a mistake again within the day with earlier DNA samples.
Over the winter, Kron reared some larvae in her lab. As of Good Fruit Grower’s press deadline in early March, just one larva had pupated, however no adults had emerged. Once they do, researchers probably will be capable to determine the pest extra particularly.
One other head-scratcher is that Kron sees no reproductive benefit for feminine flatheaded borers to put eggs in fruit. Usually, they overwinter as larva within the wooden of bushes, pupating in spring and rising as grownup beetles in early summer time. Fruit would rot earlier than then, making it a dead-end host.
It’s doable a couple of females simply acquired “confused” and mistakenly laid eggs within the fallacious host, Kron mentioned. Final yr did have bizarre climate. It’s additionally doable that is some invasive species that may’t discover its regular host.
For now, Kron and Gonçalves are asking growers to observe for harm — black spots with a leathery texture on the sun-exposed facet of fruit with no exterior frass, the telltale excretion of tunneling larvae comparable to codling moth. In the event that they really feel like slicing into one of many pears out of curiosity, high quality, however avoid wasting samples for the researchers, she mentioned.
The extension crew deliberate to start out monitoring this month, utilizing sticky triangle traps.
Chris Adams, an entomologist with Oregon State College, has not seen proof of the pest, both in fruit or in tree bark within the Northwest, the place he suspects growers additionally might mistake it for solar harm.
Nonetheless, after listening to the California story, he plans to search for it this yr and can be asking growers to maintain their eyes peeled and lower open a couple of symptomatic pears.
“We’d have a few of it right here,” Adams mentioned.
—by Ross Courtney
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