2024 - First Adult Western Cherry Fruit Fly Emergence Started June 8

Date: June 10, 2024

To: Union County News Media, Commercial Cherry Orchard Managers & Home Gardeners and Orchardists

From: Darrin L. Walenta, OSU Extension Agent Union Co.

2024 - First Adult Western Cherry Fruit Fly Emergence Starts June 16

All cherry trees owners should be aware the emergence of the first adult western cherry fruit fly is predicted to start June 16 in the La Grande area. 50% adult fly emergence is expected July 1. 100% adult fly emergence is expected July 8. Please note that eggs laid by the earliest emerging adults will hatch a few days before 50% of the adults emerge from the ground.

Initial spray applications should be made within the first week after emergence and then follow-up spray applications should be scheduled to control CFF until harvest. The insecticide product label will provide recommendations for spray application frequency and pre-harvest interval requirements. Reminder…….one spray application does not provide season-long CFF control. Adult CFF continue to emerge from the ground through late June and lay eggs into July.

Union County has a new cherry fruit fly inspector. 2024 will be Morgan Colvin’s first season as the inspector so please welcome her if you get a chance. We plan on having an informational booth at the Cove Cherry Fair so please stop by.

Cherry producers can run the predictive model at your own convenience by visiting the Online Phenology and Degree Day Models website at https://uspest.org/dd/model_app (select the Ali Niazee 1979 western cherry fruit fly model and the weather station nearest your location.

Management Options for the Western Cherry Fruit Fly (CFF) include:

1) Spray your own tree(s) with registered insecticide products. See “A Few Pointers for Spraying Backyard Trees” section towards the end of this letter.

2) Hire a licensed commercial pest control company to spray your tree(s). It is best to hire the company in early to mid-May so they can prepare in advance of CFF emergence. To locate potential service providers, check the yellow pages for commercial pest control companies (CPCC).

3) Remove all blossoms or fruit from your tree(s) prior to CFF emergence.

4) Voluntarily remove any tree(s) if you never pick the fruit nor manage pests in the trees.

• Fruit trees not used for fruit production (e.g. “shade” only) should be replaced with a true shade tree species. Fruit trees can harbor a variety of insect and disease pests that can/will impact neighboring trees so pest management is critical.

Tree height and canopy influence effectiveness of sprays. Shorter trees pruned to open up the canopy allows for more effective spray coverage. For further information on the cherry fruit fly management and products for CFF control, please contact the Union County Extension Office (963-1010) or refer to the following references:

2024 PNW Insect Pest Mgmt. Handbook https://pnwhandbooks.org/insect

EC 631 Managing Diseases and Insects in Home Orchards https://catalog.extension.oregonstate.edu/ec631

Be sure the insecticide you choose is labeled for use on fruit/cherry trees. Always read and follow label directions for safe pesticide use, personal protective equipment (PPE), frequency of application, and pre-harvest intervals.

CFF Biology Notes: Cherry fruit flies spend about 10 months out of the year as pupae in the soil. For the first week after emergence, adults feed on any available sweet substances & moisture. Adults begin laying eggs in fruit 7 days after emergence. Adult emergence continues for up to 2 months. Eggs hatch within 7 – 10 days then larvae feed in the fruit for 2 – 3 weeks. Larvae then emerge from the fruit, drop to the ground and pupate in the soil over-winter until this time next year.

A Few Pointers for Spraying Backyard Fruit Trees

Many homeowners may consider spraying their own fruit trees due to limited availability of licensed pest control companies. The window of opportunity for managing many fruit tree diseases has passed but insect pest management needs are ramping up. Here are a few pointers to consider before attempting a spray application to fruit trees:

 Thoroughly cover the entire canopy and tops/bottoms of leaves. You will need a sprayer powerful enough to reach to the top of the tree canopy. It is not a safe practice to stand on a ladder to make any application!

 Choose the right sprayer with the right spray volume capacity for the job.

­Trombone or slide-type sprayers; small powered sprayers with appropriate spray gun/wand; and a few specialized hose-end sprayers are designed to deliver diluted spray to the tops of mature, standard-sized fruit trees. Always use an anti-backflow device with hose-end sprayers to prevent back-siphoning of pesticides into your home water system. ­

Small hand-held pump sprayers and backpack sprayers do not have the power nor volume capacity to spray mature trees.

 Determine spray volume needed for a tree by applying clean water to the tree with the selected sprayer. Some large trees may require up to 10 gallons of spray solution, whereas, small trees may need only 0.5 to 1.0 gallon of spray solution.

 Correctly identify the target pest then apply the proper dosage of the correct pesticide at the correct timing for the target pest.

 Do not apply herbicides with the same sprayer used for fungicide/insecticide applications to fruit trees.

 Choose a pesticide registered for use on fruit trees (see label) then follow all safety precautions on the label to ensure safe pesticide use, frequency of application and preharvest intervals.

 Wear proper personal protective equipment (PPE) for overhead spraying. See label for recommendations.