The allium leafminer, a tiny fly whose larvae infect leeks, onions, garlic, chives, shallots and green onions, was first discovered in December on an organic farm in Lancaster County, Pennsylvania. Since then it has been identified on two farms in Lehigh County. Chester, Dauphin and Delaware counties have also confirmed the pest.
"The initial report [in Lancaster] was turned in by an organic grower who was reporting 100 percent loss" of onions and leeks, said Sven Spichiger, entomology program manager for the Department of Agriculture. "When you get 100 percent crop loss, it causes you to spin your head."
The leafminer likely arrived the way most other invasive species have, stowed away in cargo shipments from overseas.
At 3 millimeters long, the leafminer is easy to miss. But it can cause outsized damage.
"We do a lot of garlic so obviously we're concerned about it," said Dax Funderburk, who grows about 10,000 bulbs of garlic on a quarter-acre of his Beets Workin' Farm in Mertztown.
"Because we grow sustainably we don't use pesticides, so it's maybe more challenging for us than for a conventional grower," Funderburk said.
Indeed, research suggests the pest is a greater threat to organic, non-commercial farms, which eschew pesticides in favor of plant coverings and other means to keep pests down.
"It's becoming more and more challenging," Funderburk said. "There's not a lot you can do unless you're going to go to the expense and trouble of covering everything with insect matting, which is not 100 percent foolproof."
It's also expensive. A 600-foot roll costs nearly $1,000.
The adult leafminers appear around March. The females lay eggs on the base of stems, and emerging larvae mine downwards, feeding on the bulbs.
Damage caused by feeding and mining results in softening of the plant parts and increased susceptibility to bacterial and fungal infections. The leaves of infected plants appear wavy, curled and distorted with a row of white dots.
Onions, garlic and related plants aren't major crops in Pennsylvania. The National Onion Association, a trade group, says fewer than 800 acres of Pennsylvania farmland are dedicated to that crop, compared to 23,000 acres in the state of Washington. And the overwhelming majority of the nation's garlic production is in California.
Even so, "for our farmers an infection of this pest could mean a loss in production of allium crops," Agriculture Secretary Russell Redding said in a statement. "And for our consumers, this could result in a lack of availability of these crops for consumption."
Source: mcall.com
