New pest threatens apple orchards

Okanagan orchardists are trying to wrap their minds around another new pest that could be devastating to apple trees.

Apple clearwing moth

There’s another a new insect pest of apple trees that’s moved into the Central Okanagan.

The first apple clearwing moth appeared in orchards in the Similkameen in 2005 and today that area is generally infested with the borer that damages trees by feeding under the bark during the larvae stage.

Entomologist Gary Judd, a research scientist at the Pacific Agri-food Research Centre in Summerland says he conducted a comprehensive study in orchards from the border to Salmon Arm last summer, trapping in every block of orchard. From those results, he created maps showing the pest’s presence and in what numbers.

It shows that areas like Rutland and Ellison are pretty well infested with the new pest, while there are few in West Kelowna and Mission, for instance.

The maps are available on the website of the Sterile Insect Release program at: www.oksir.org

The extent of its spread was a surprise, he admits. He speculates they must move on vehicles or in trees that are being moved.

“Soon it will be everywhere,” he says.

In orchards where it hasn’t yet been identified, growers should monitor for it by hanging traps, and if there are 1 to 50 moths in a trap, mating disruption is available to control it.

However, it’s better done by groups than by individual orchardists, he said, since it can easily fly to nearby orchards.

When levels get too high, mating disruption is not very effective and growers should plan on spraying the trunk of each tree with an approved pesticide to keep them under control.

He says it’s difficult to assess the economic impact of the new pest. Some growers are very alarmed and they’re seeing the damage on their trees, but he says others aren’t seeing much damage.

Ideally, prevention would be as simple as not bringing material in from an infested area, and it’s suspected that’s how the clearwing moth arrived in North America.

At last Friday’s SIR board meeting in Kelowna, the B.C. Fruit Growers’ Association appealed to the board for help in conducting area-wide monitoring and control.

However, the board said it’s too late this year, but that if growers want assistance next year, they must let the SIR board know by the end of this year.

BCFGA general manager Glen Lucas said the industry is preparing a funding request to implement a three-year, area-wide pilot project, in cooperation with the SIR program to evaluate the effectiveness of mating disruption for control, so extra staff can be hired.

He said growers are encouraged to examine area maps to see if it’s in their area, and to use mating disruption dispensers to control it.

Judd said backyard apple trees are just as susceptible, but he didn’t think they would become a source of re-infection of commercial orchards as is the danger with codling moth.

In fact, he said backyard trees are generally not dwarf trees, and the big ones aren’t affected as much, so homeowners likely won’t notice damage from clearwing moth.

 

jsteeves@kelownacapnews.com

 

 

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