Now is the Time to Get Ready to ORGANICALLY Fend Off Wormy Apples and Pears

Advice from the UC Master Gardener of Contra Costa Help Desk

Client's Question:  

I ended up last summer and fall with a harvest of wormy apples and pears. What can I do to prevent that this year?

CCMG Help Desk's Response:
You most likey have codling moths. By the time you see the damage, typically at harvest, it is too late to protect that year's crop - your preventative tactics need to take place now, in the spring.

Codling Moth
Cydia pomonella

Codling moth is a common and serious pest in Contra Costa County's home-grown apples, pears, and even in walnuts, but calls received at the Master Gardener Help Desk are almost always about apples and pears.  And those are not really worms, either, but rather caterpillars, a common term for the larvae of butterflies and moths. 

You probably would never even notice the adult moth, Cydia pomonella, as it is only about ½ to ¾ inch long with mottled gray wings, and it is only active a few hours before and after sunset.   The adult moths emerge from pupation in early spring; the female mates then lays her eggs (30-70) on either leaves or fruit; the eggs hatch and the larvae chew into the developing fruit.  The larvae continue to develop inside the fruit where they are protected from any chemical controls.  When larvae are mature, they exit the fruit to pupate in the soil or on debris under the tree or in bark crevices.  The cycle then starts all over again with 2 generations per year in tContra Costa County's Bayside areas (e.g., Richmond, El Cerrito) and 3-4 inland (e.g., Concord, San Ramon, Brentwood).   The most effective approach is to manage the first generation of the season.   Left unmanaged, codling moth can infest up to 90% of the fruit.  To reduce the population of this pest without toxic chemicals you can use trapping and sanitation techniques.

Traps:
Codling moth pheromone traps (sticky traps laced with pheromone) attract and capture the males. Fewer males make it more difficult for the females to mate.  Hang traps starting in mid March (inland areas) to late March (coastal areas) when the emerging adults are expected to start flying.  Use one or two per small tree and two to four per large tree and hang them high in the canopy.  Codling moth pheromone traps are typically available at hardware stores, garden centers, or online.

Information on a home-made codling moth bait trap can also be found on UC MGCC Program's web site at http://ccmg.ucanr.edu/files/48135.pdf.

Sanitation:
Sanitation should be an integral and early part of any codling moth control program.  Beginning about six to eight weeks after bloom, start checking fruit for sawdust-like filled holes (larvae entry holes in the fruit).  Check every week or two and remove the infested fruit from the tree and the ground. Dispose of it in your yard waste, not your compost pile.

Sanitation and trapping may be all that is needed when you have an isolated tree and low codling moth populations.  But, if populations have been allowed to build up over a number of years (or your neighbors haven't managed their trees) you may need a more aggressive approach to achieve satisfactory control (and maybe your neighbor's cooperation).  For even more information on aggressive management of codling moths, including even more organic actions, go to the UC IPM Online--Statewide Integrated Pest Management website: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7412.html.

Good luck on "worm" free apples and pears this year.. 

Contra Costa Master Gardeners Help Desk
This Help Desk response was originally written by Emma Connery for publication in the Contra Costa Times in February 2010. It has been been updated for thie blog and any errors are the responsibility of the current HD blog editor.

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Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/