What Do You Spray Codling Moths With?
As the weather warms and we enter the apple, pear, and walnut growing season, attention will turn to the invasive codling moth caterpillar and the preventative strategies needed to keep it under control. This pest can cause severe damage to commercial orchards and backyard plantings.
The most important part of an integrated pest management (IPM) program for codling moth is prevention. Sanitation, thinning fruit to reduce egg-laying, and monitoring for eggs, larvae and pupae are all necessary to limit damage. When the threat of moths is high, a chemical spray will be needed. However, there are ways to minimize use of synthetic insecticides in home orchards, including careful thinning and fruit bagging.
While it is not possible to eliminate codling moth entirely, the use of nonchemical control methods should be maximized. Preventative practices such as removing infested fruit, thinning out trees, and reducing tree overcrowding can significantly reduce the need for chemical treatments. Additionally, selecting varieties that are less susceptible to codling moth damage, particularly early-maturing apples and pears and late-leafing nut trees can help limit damage.
Insecticides are used to kill moths and their larvae before they can attack the fruit inside, but even in a moderate infestation, repeated applications will be necessary for clean harvests. Spraying should begin when the first generation hatches and continues throughout the season.
Several organic and conventional insecticides can be used to control codling moths. Bacillus thuringiensis, pyrethrum, and rotenone are low toxicity materials that haven’t been very effective when applied alone, but when combined with granulosis virus or spinosad they can provide effective control. Horticultural oil has also been shown to be effective, but it can require multiple applications and can be toxic to beneficial insects.
A new biological agent called CYD-X or granulosis virus, has been effective in reducing damage in California home orchards. This product works by infecting the digestive system of the codling moth larvae and killing them. It is not effective against adult moths and has no effect on other plants, but it is OMRI listed for certified organic production and can be applied weekly during egg hatch through the end of the worm stage.
Conventional and organic fungicides can also be effective against codling moths, but are not as good at controlling mature larvae. Fungicides with the active ingredient azadirachtin or neem oil are especially effective.
Increasing the number of natural predators can also be helpful for controlling codling moths. Providing habitat for birds, bats and other predatory insects such as assassin bugs and parasitic wasps can reduce pest populations. Release of entomopathogenic nematodes can also suppress codling moths, but they have not been proven to be effective in the Intermountain West. More information on attracting and encouraging natural predators can be found in WSU’s resource, Birds and Bats for Pest Suppression in the Orchard.