Codling moths are a problem in apples and pears. June 6 is the projected best date to start spraying in the Castle Country. The cool spring this year has delayed codling moth flight and egg hatch by about two weeks.
Codling moths start to fly and mate when the weather gets warm enough. We use traps to see when the male moths are flying and then keep track of the local temperatures to determine when the eggs will hatch. Spraying too early is a waste of chemical. Spraying later will result in some worms in the fruit. One hundred percent control is not realistic so gardeners need to decide how much fruit damage they are willing to tolerate.
There are 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. Cleanup 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 2-3 weeks. The method is most effective for smooth-barked trees.
Chemical controls fall into two categories, soft insecticides and synthetic insecticides. Whenever possible, the soft insecticides are more desirable than 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. Use of the harsher chemicals tends to promote spider mite populations later in the season, as the beneficial insects have also been killed by the spray.
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. After the application of horticultural oil a bag can be tied around individual apples to keep any additional infestations off the apple. Plastic bags may be used.
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 my 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 we end up with spider mites later in the season. Pyrethroids (permethrin, bifenthrin, cyfluthrin, & etc.) are another broad spectrum class of chemicals that may be used but have a tendency to reduce beneficial insect populations.
Timing is critical. The general rule of thumb, in the absence of more specific information, is to begin your 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 moth. A 21 day spray interval would require only two applications for the first generation.
For more information on codling moth control please stop by the Extension Office and pick up the Utah State University fact sheet on codling moth.
Home apple growers who wish to be on the codling moth hot line may call the Extension Office. Your name and number will be placed on a list to call when the time has arrived for applying your first cover spray. May you have a fruitful season.
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.
Ron Patterson is the Utah State University Extension Agriculture Agent for Carbon County. He can be reached at 435-636-3235. Utah State University is an affirmative action/equal opportunity institution.
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