When apple maggots targeted my plum tree, it was war

Last month I described the apple maggot, an insect that is causing big problems for Western Washington fruit growers. It gets into apples and tunnels around in the flesh, spoiling the fruit. This year we have seen it in plums as well. It was the most common insect question that we got at the Washington State University Extension master gardener desk this year in September and October.

This pest has become a problem for me personally. I’ve been doing some research and I promised to report on the management strategy that I’m going to use.

To begin with, I collected and disposed of fallen fruit every few days to reduce the population next year. Surround At Home Crop Protectant is the recommended spray. This spray makes the tree dusty looking and discourages insect egg-laying. Unfortunately, it also requires reapplication every seven to 14 days for several months.

Commercial orchardists use sticky traps to time their pesticide sprays. Backyard growers realized that they could get by without the pesticide if enough of the flies could be trapped. This made sense to me.

You hang bright yellow rectangles or red spheres in your tree at about eye level. The traps are covered with a sticky substance and often effectiveness is enhanced by using a chemical lure, such as ammonium acetate, to make the trap smell like a fruit.

In two to four weeks the traps get filled with insects and/or lose their tackiness and will need to be cleaned or replaced. Scraping and regooping is a tedious process, so hobby orchardists suggest you cover your trap with a plastic sandwich bag to begin with, and then you can peel that off to start again.

I like an even simpler idea. Rather than trying to make your traps look and smell like fruit, you just use real fruit: little “lunchbox” apples. I’ll coat them with a nontoxic sticky material. It’s available under several brand names at any good nursery or by mail order from most nurseries that sell fruit trees.

By June 1 the fruit traps will be securely wired to a branch on the sunny side of my trees. Nearby leaves and fruit will be removed, so the flies can zero in on them easily. I’ll place two on each of my dwarf apples (those less than 10 feet tall) and two on my little plum. My standard trees will require six to eight traps. When they need replacing, I will put the old ones into a garbage bag.

One of my biggest problems is neighborhood host trees. Beside apples and pears, crabapples and ornamental hawthorns are also susceptible to apple maggot. These insects are not strong fliers, but any host tree within to mile could serve as a breeding ground and source of infestation for my trees. To be successful, I’m probably going to have to convince my neighbors to manage their trees or to remove them.

More garden fun in November

Have you sown a cover crop yet? If not, there is still time to plant fava beans. Cover crops (also called green manures) improve your soil when you turn it under in the spring.

This is the perfect time to add lime to your soil, if it is needed. Six pounds per 100 square feet every two years is about right for most loamy soils. Clay soils need more, but only every three years, and sandy soils need less. Get a soil test for specific recommendations for your soil.

Move any container plants that are very exposed to a more protected location. Roots are the least hardy part of a plant. Plants that would be perfectly hardy in the ground can be killed when planted in pots.

It’s garlic planting season. Garlic planted by midmonth generally produces more plump, pungent cloves than spring-planted garlic.

Lawns need another fertilizer application late this month. To keep your lawn in good shape, plan to work off your turkey and pumpkin pie by pushing around the fertilizer spreader.

Holly Kennell is the Snohomish County extension agent for Washington State University Cooperative Extension. Master gardeners answer questions on weekdays at WSU Cooperative Extension – Snohomish County, 600 128th St. SE, Everett, WA 98208. Call 425-338-2400.