2013 Annual Report
The project goals are to determine the use of apples and hawthorns by apple maggot fly populations in Washington state and to determine if major tropical fruit crops grown in Asian markets can be hosts of apple maggot flies. Apple maggot is a barrier to trade between Pacific Northwest apple growers and Asian markets because of the possibility of the fly establishing in Asian countries via infested fruits from the Northwest. Technical objectives are to provide data on (1) use of different varieties of apples as hosts by hawthorn- and apple-infesting apple maggot flies in Washington state; (2) use by apple- and hawthorn-infesting apple maggot flies of apples that are off trees, such as storage bins or on the ground; and (3) non-use of various tropical fruits by hawthorn- and apple-infesting apple maggot flies in Washington state. To determine if apple maggot flies from hawthorns prefer apples, we completed testing of 20 pairs of apple maggot flies reared from apple and 20 from hawthorn that were exposed to Gala apples. We found that 40% of flies from apples attacked apples, whereas only 10% of flies from hawthorns attacked apples. To determine if picked apples are at risk for infestation by apple maggot flies, we initiated tests on use of apples off trees in bins by flies. Five containers of apples were placed under apple maggot-infested trees at one site in July 2013. Results will be obtained in September 2013. To determine if tropical fruits are susceptible to attack by apple maggot flies, we conducted tests of tropical fruit use by apple maggot flies beginning in mid-July 2013. We hung apples, mangoes, kiwis, papayas, and oranges in 20 apple trees in one site and an additional 10 apple trees in another. Apple fruits were infested, but so far no tropical fruits have been infested. To determine if peaches are attacked by apple maggot fly, we sampled a commercial peach orchard located about 20 m from heavily infested apple trees beginning July 2013. Dropped peaches from under 200 peach trees were sampled and brought to the laboratory for rearing of larvae. In addition, sticky yellow traps were hung in trees to catch adult flies. We also hung peaches in heavily infested apple trees. We are gathering data at the moment and have shown preliminarily that flies commonly enter peach orchards but do not attack the fruit. We are in the process of meeting all the technical objectives, and will provide data to stakeholders by winter 2013. This will address the overall project goals by showing that apple maggot flies from hawthorns rarely use apples whereas apple maggot flies from apples frequently use apples. As most flies around apple growing-regions develop in hawthorn and not apple, the presence of hawthorn flies represents less a threat to apple orchards than the presence of apple-origin flies. In addition, tropical fruits are not threatened by apple maggot flies, potentially reducing the impact of the fly as a barrier to foreign trade.