Delimitation and possible eradication or control of the apple maggot in the Umatilla County, Oregon

In 1979, the Apple maggot (AM), Rhagoletis pomonella (Walsh) (Diptera, Tephritidae) native to the Eastern US, was first detected in Oregon. Since then, it has been reported for the Willamette Valley, Hood River and the Pendleton area posing a serious threat to the apple production in Oregon.

The Apple maggot belongs to a complex of four sister species: Rhagoletis mendax (blueberry maggot), R. cornivora (dogwood berry maggot), R . zephyria (snowberry maggot) and R. pomonella. Originally it fed in the fruit of wild hawthorn (Crataegus spp.), but during the past 130 years it has become a primary pest of cultivated apples, especially in the northeastern United States and southeastern Canada.

The Oregon Department of Agriculture is trapping for AM in Eastern Oregon, in particular in the Milton-Freewater area, for more than 17 years. In 2000, one AM was recorded in Echo on crab apple, three AM in Arlington, one AM in Moro and Condon. Eradication efforts immediately implemented by ODA, OSU and local authorities in Arlington and Echo were successful in eradicating the Apple maggot population. In 2001, more than 60 AM were caught in Southwest Pendleton on ornamental hawthorn. A delimitation survey in 2002, recorded 387 specimens around the Blue Mountain Apartments in Southwest Pendleton. In a combined effort between homeowners, OSU, ODA and the Milton-Freewater private apple industry, host trees were either removed or sprayed. Due to economical limitations the spray actions were stopped after two applications. Continuous surveying in 2004 and 2005 by ODA and OSU shows positive trap catches for the Southwest part of Pendleton but is so far negative for the Milton- Freewater area.

A potential spread of AM to the Milton-Freewater area would put at risk the local apple production and result in an significant increase of pesticide use. Pesticide applications by commercial apple producers as well as homeowners will result in a significant increased level of pesticide residues endangering the Oregon watersheds and riparian forest trees.

The 2006 AM eradication project started in June 23 with removing 70 hawthorn trees at the Blue Mountain (BM) Apartment complex. On the remaining 29 trees, yellow sticky baited AM traps were hung. All traps were additionally baited with a Trece 5g- ammonium bi-carbonate lure. By the end of June, a total of 422 traps were placed between Pendleton (248 traps), Weston (10), Adams (4), Athena (10), and Milton- Freewater (150) including several sites along the Umatilla River and other rivers. Traps were serviced weekly at the Blue Mountain Apartment complex and biweekly for the other areas.

In order to prevent AM hatching from the soil more than 400 meters of fine insect proof netting was securely placed on the ground along the drip line of the hawthorn trees at the south and west side of the BM Apartment complex.

On June 29, a licensed pesticide company applied Provado (active ingredient: imidacloprid) on the ground below the hawthorn trees at the Blue Mountain Apartment complex. On July 7, all remaining hawthorn trees were canopy sprayed with Success (active ingredient: spinosad). The Success application was repeated on July 21. The chemical control was paid for by the Milton-Freewater apple industry.

The first AM was caught in the week of July 3-7 at the Blue Mountain Apartment complex. In total, 135 AM were caught over a period of four months at the Blue Mountain Apartment complex. One AM was caught in a trap at the USDA Forestry Building about 50 meters below the Blue Mountain Apartment complex. No other AM was caught in any other trap outside the BM Apartment complex.

Traps outside a 0.5-mile radius around the Blue Mountain Apartment complex were removed by mid September. At the Blue Mountain Apartment complex traps were removed by mid October.

In addition to Umatilla County AM traps were also placed in La Grande, Union County (40 traps) and in the Ontario area, Malheur County (21 traps). All traps were negative for AM.

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