Organic Sprays to Kill Worms in Peach Trees

Bacillus Thuringiensis

• The National Sustainable Agriculture Information Service recommends Bacillus thuringiensis -- known as Bt for short -- to control peachtree borer in organic orchards. This formulation contains bacteria that naturally attack certain caterpillar species in the wild. The peachtree borer, lesser peachtree borer and peach twig borer are all susceptible to the bacteria.

When to Spray

• Several properties of Bt make it vital to correctly time the application of the spray to your trees. Bt does not remain active for long after spraying, so you will need to apply it weekly in order to have an effect. Spray the trunk where the larvae will enter the tree and spray during the midsummer, the peak season for adult moths. Contact your local cooperative extension office to learn the specific time when adult peachtree borer moths are active in your area.

Advantages and Disadvantages of Bt

• Bt has become a popular organic alternative to synthetic insecticides because of its high level of safety. Because it only targets specific insects, beneficial insects and pollinators are not harmed. Bt is safe for people, pets and wildlife and because of this, most formulations allow spraying to occur right up to harvest. Particularly when spraying trees, this reduces the risk of harm from pesticide drift onto neighboring crops.

  Bt does require the insect to consume the product in order to work. This makes timing important to ensure that the caterpillars ingest the product as they burrow into the tree. Within hours, Bt paralyzes the caterpillar's digestive system and stops damage to the tree. However, caterpillars generally live for a few days before succumbing to starvation, so you may see living caterpillars even after spraying.

Other Organic Alternatives

• The parasitic nematode Steinernema carpocapsae also infects and kills peachtree and lesser peachtree borer caterpillars. Unlike Bt, you will apply this product as a drench to the lower trunk in the fall or spring. If you have only a few trees, you can physically remove existing insects using a piece of wire to dig them out of their burrows. Check the roots below the soil line as well, as caterpillars can burrow there as well. Although some growers paint the lower trunk with latex paint to discourage the caterpillars from boring, the National Sustainable Agriculture Information Service says that this is not a method approved for certified organic orchards. Removing dead leaves and branches from beneath trees and keeping trees healthy will reduce the incidence of pest problems.