The worm in your apple is usually actually a codling moth larvae!
Often found inside apples, pears, and walnuts as the light pink worm that’s beaten you to the crunch, the codling moth, Cydia (Laspeyresia) pomonella, is a common orchard pest that can survive between seasons, and if left unchecked, can consume 20 to 90 percent of an orchard tree’s fruit or 10 to 15 percent of walnuts.
Distinguished by a dark, coppery brown band at the tip of the moth’s mottled grey wings and ½ to ¾ inch in size, the codling moth overwinters in thick, silken cocoons in bark crevices or in soil at the trunk’s base and is largely inconspicuous. Larvae pupates during early spring and adults emerge between mid-March to early April, with the moths active a few hours before or after sunset, and mating when the temperature reaches 62 degrees Fahrenheit.
The codling moth lays 30 to 70 tiny, disc-shaped eggs on fruit. Upon hatching, the larvae bur into fruit in a drive to feed upon the fruit’s developing seeds or the nut’s kernel, leaving behind reddish-brown tracks called ‘frass.’ Burred fruit and nuts fall to the ground, where moths may continue to regenerate in the soil.
Codling Moth Management Strategies
While codling moth populations can be difficult to control and can be concerning for small-scale and backyard orchards, there are several organic and preventive measures one can take to protect trees, fruit, and other beneficial insects that otherwise might be compromised by commercial lures like bug lights. Timing is essential for keeping this pest in check, so be sure to do adequate research depending upon the chosen strategy. For a more expansive list of techniques for protecting orchard trees against codling moths, consult this wonderful guide from The Colorado State Extension. A few strategies are summarized below.
Beneficial Strategies: Preventive Measures
Select varieties that are less susceptible to damage – Choose early-maturing apples and pears, and late-leafing walnuts.
Employ good sanitation practices – Remove and destroy infected fruit and those that appear with ‘stings’. In late winter, rub off loose bark from the trunks of older trees, which may provide nesting sites for moths, and likewise, clear debris from beneath trees.
Thin fruit – This helps to reduce points of entry for codling moth, which can jump from fruit to fruit, and increases coverage of protective foliar sprays. Reducing apples and pears to no more than one per cluster can greatly reduce the incidence of codling moth and other pests damage.
Trunk-Banding – Create bands with strips of corrugated cardboard 1 ½ to 2 inches wide, and attach where there is a transition from smooth to rough bark – stapling around a branch or trunk. Alternatively, use burlap as a band. Purposely providing areas for pupation for codling moth will prevent the moths from burrowing into fruit. The bands should be removed and replaced daily for best effect and at least every 2 weeks to coincide with the end of a generation.
Bag Fruit – Enclose growing fruit ½ to 1-inch in diameter in plastic sandwich bags or paper lunch bags to protect the fruit from predation.
Beneficial Strategies: Trapping Moths
- Homemade Lures: Attract codling moths with fermented sugar-based lures placed in open container (i.e. a plastic milk jug or 2-liter soda bottle) with a solution like molasses diluted 1:7 in water, fruit juice, or beer with a few drops of soap added. Tutorial, here.
- Pheremone traps: Commercially available pheremone traps (www.arbico-organics.com/product/codling-moth-trap-pheromone-lure-sticky) can help reduce populations and are very useful in determining when codling moths are active and thus when to spray or use other techniques.
Beneficial Strategies: Sprays
Spinosad – A naturally derived material produced by soil microbes that, when combined with horticultural oil, is beneficial for increasing control and fruit coverage. Apply in 10-14 days intervals when the eggs are hatching; reaching a maximum of six applications per season.
Kaolin Clay – A low-hazardous application that can be applied to fruit as a barrier to codling moth egg laying and entry into fruit. Allowable in Certified Organic production. Information on application here: Extremely Green
Codling moth granulosis virus – A mail-order virus available from garden/farm supply companies and sold under the name CYD-X that is specific to codling moth, and when ingested, produces a disease that kills larvae within 3 to 7 days. Made into a spray and applied to foliar growth and fruit in late spring or early summer when eggs of first generation codling moth begin to hatch. Additional applications applied mid to late summer.
For more information on codling moth and management strategies: