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Fighting off the codling moths in apple orchards

USU extension

An apple with a codling moth larva in it.

The apple tree blossoms are falling.

Is it time to spray for worms?

The codling moth is the beast that is responsible for worms in Carbon County apples.

Codling moths start to fly and mate when the weather gets warm enough. The best recent research uses an accumulation of warmth to determine when the moths start flying. This information is helpful as it will help us determine when the optimal time to spray for effective control is.

When spraying is done too early time, effort and money is wasted because there is nothing to control. When spraying is done too late the results are not desirable. Since there isn't a good source yet to help determine the current status of the codling moth in Carbon County an extrapolation of similar counties is the next best option.

The most vulnerable stage of the codling moth life cycle is the larval stage, just before they burrow into the fruit. That is why timing of the spray is critical. It is also possible to trap them when the larvae travel down the trunk to pupate. However, disrupting the mating of the adults is not effective in small orchards.

While chemical controls can be used, orchard owners should first examine two management practices that will help reduce codling moth populations�sanitation and trunk banding.

Any unharvested or culled apples should be removed from the orchard and destroyed or properly composted. This includes apples that drop early (late June through July) as they may already be infested. Clean up and properly compost leaf piles (away from the orchard), brush, fruit bins, wood piles and other debris. This will help reduce the pupation sites for future generations.

Trunk banding is a practice that will help reduce subsequent generations of codling moths. Wrap cardboard bands (2-3 inches wide) around the tree trunks with the flutes parallel to the trunk. As the larvae travel down the trunk they crawl into the cardboard to pupate. Place the bands mid-May to late-June for the first generation of larvae and again mid-August through late-October for the second generation. Replace and destroy the bands every two to three weeks. The method is most effective for smooth-barked trees.

Chemical controls fall into two categories; soft insecticides and synthetic insecticides. Insecticides should be selected and applied in such a way as to reduce the harmful effects to beneficial insects such as pollinating bees and predatory insects and mites.

Soft insecticides are usually not as effective but in conjunction with sanitation and trunk banding described above provide control satisfactory for most home orchards. Bacillus thuringiensis has not proven very effective even when applied weekly. Horticultural oils have been successful to some degree by suffocating eggs before they hatch. Excessive use of horticultural oils may affect the appearance of the fruit, but that is usually more desirable than a worm hole.

Synthetic insecticides tend to be more harmful to beneficial insects and mites. These products tend to be pulled from the market from time to time so what was an approved product last year may not be this year. Malathion and spinosad would be the first choice as they are less harmful to beneficial creatures. Sevin (carbaryl) may also be used but has a tendency to reduce beneficial populations and then orchards end up with spider mites later in the season.

Timing is critical. The general rule of thumb, in the absence of more specific information, is to begin a spraying program 10 days after full petal drop. Subsequent applications should follow the label of the product being used. If sprays are being applied 10 days apart three applications should be applied for the first generation of codling moths. A 21 day spray interval would require only two applications for the first generation.

This article is not an endorsement of, or a guarantee of, the effectiveness of any chemical product. Be aware that using a pesticide, except as registered by the manufacturer, is a violation of the law. Always read and follow the pesticide label.

Home apple growers who wish to be on the extension offices codling moth hot line may call 636-3235. Your name and number will be placed on a list to call when the time has arrived for applying the first cover spray.

For more information on codling moth control please stop by extention office and pick up the Utah State University fact sheet on codling moth.

Ron Patterson is the Utah State University Extension Agriculture Agent for Carbon County. He can be reached at 435-636-3235. His office is located in the Carbon County Courthouse.

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