Regular spraying recommended to prevent infestation

Photo by Ann McCrearyEven feral trees need to be treated to avoid a widespread apple maggot infestation.

Photo by Ann McCreary
Every apple tree in an affected area, even feral trees, need treatment to avoid a widespread apple maggot infestation.

By Ann McCreary

In an effort to head off any possibility of an apple maggot infestation, Okanogan County’s pest control agent is urging anyone with apple trees on their property to spray them for apple maggots.

Last year 32 apple maggot flies were caught in insect traps that are placed every summer in apple trees around the county to detect the presence of apple maggots, which can pose a serious threat to the commercial apple industry.

The flies were caught at 18 sites in Okanogan County; 15 of those sites were in the Methow Valley.

While 32 flies may not sound like a lot, any number is worrisome, said Dan McCarthy, county pest control agent. These were the first apple maggot flies found in the county since 2011.

“It was alarming. All of a sudden we had 18 positive trap sites in Okanogan County in one year,” he said.

The 15 positive trap sites in the Methow Valley extend from Carlton up the Chewuch drainage. They represent 14 different properties because one location had two positive traps.

McCarthy sent letters to all property owners in the county where traps captured apple maggot flies, and has also contacted many of those property owners in person or by phone to urge them to spray all their apple trees.

Under state law, property owners have a legal responsibility to manage insect pests in their trees.

The appropriate time to spray in the Methow Valley begins in mid-July, and spraying should continue on a weekly basis through September, McCarthy said. Everyone with apple trees on their property, whether in an orchard, a yard, or feral (uncultivated) trees, should spray, he said.

“We are trying to make the greatest effort to see if we can stop this in its tracks,” McCarthy said.

Consistent spraying

Spraying apple trees for apple maggot flies is not difficult, but needs to be done consistently from July through September, he said.

“There are products available labeled for apple maggots at the hardware stores. If people are spraying for coddling moths, that would cover apple maggots,” he said.

“It takes a few minutes per tree, depending on the technique used” to apply the spray, McCarthy said.

In addition to conventional spraying, “there is an easy to apply attract-and-kill bait that is organically certified … that takes about a minute per tree,” he said.

People who have questions or want more information about spraying can contact McCarthy at (509) 322-1286 or email

Apple maggots hatch from eggs laid under the skin of the fruit by flies. The egg laying begins in July and continues through early October. The maggots burrow through fruit, making it brown, mushy and inedible.

Last summer’s trapping found no apple maggots in the 28,000 acres of commercial apple orchards in Okanogan County, but finding the flies in trees anywhere in the county is a real concern to growers, McCarthy said.

Apple maggots are spread mostly by people transporting apples from infested backyard apple trees to non-infested areas of the state, according to WSDA. Quarantines are put in place to protect Washington’s commercial apple industry.

If the pest became established in Okanogan County, McCarthy said, the county could face quarantine, meaning fruit grown here would have to be inspected and certified as pest-free before it could be shipped from the county. In some instances only particular areas of a county are placed under quarantine, he said.

One commercial orchard near Okanogan is within one-half mile of a site where an apple maggot fly was caught last summer, and is therefore required by the Washington State Department of Agriculture (WSDA) to have all fruit inspected and certified.

WSDA placed about 300 traps in Okanogan County last summer and will increase the number this year to monitor for the presence of apple maggot flies, McCarthy said.

“In every place with positive traps [last season] they will do high-density trapping,” to determine if flies are still at those sites, he said.

After the results of this summer’s trapping are analyzed, state and county agriculture agents will know whether last year’s increased number of flies was an anomaly, McCarthy said.

“We won’t know the results of the trapping until mid-September” because the flies have to be positively identified in a laboratory since they resemble other insects, he said.

Protecting an industry

When those results are known, pest control officials will determine whether there is an infestation and whether measures such as quarantines need to be put in effect in order to protect Okanogan County’s $250 million tree fruit industry, McCarthy said.

A small commercial grower himself, McCarthy said the financial and logistical burdens imposed by quarantines, inspections and eradicating apple maggots are something everyone in Okanogan County’s tree fruit industry wants to avoid.

The presence of flies in the Methow Valley is a concern, he said, because “from Carlton upstream there are so many feral trees.” Many are left over from decades past when the Methow Valley had a more active orchard industry, he said.

Among the property owners in the county with positive sites that McCarthy has contacted, “several have responded and asked for recommendations on what to use and what the timing [for spraying] is,” he said.

In addition to the 15 positive trap sites in the Methow Valley, apple maggot flies were found at sites in Pateros, Okanogan and near Loomis, McCarthy said.