Monday, August 29, 2011

Peachtree borer identification and control

 The peachtree borer, AKA peach crown borer, (Synanthedon exitiosa) is a major pest of peach, nectarines, cherries, plums and other members of the genus Prunus whether grown for fruit production or as an ornamental.  The adult is a clear-wing moth resembling a wasp.   “The female is dark metallic blue with a broad, reddish orange band around the body on the fourth abdominal segment. The male is smaller with a shiny, dark metallic blue body”. [i] 

Male and female photos courtesy of

When eggs are laid at the base of a peach or other stone fruit tree, the worms eat through the bark and feed on the cambium and inner bark (phloem) of the tree. Both the lower portion of the trunk and the upper roots are damaged.
Figure 3: The initial feeding activity of the borer will appear
as translucent goo that oozes from the ground.
 Figure 4: As the feeding continues, the goo will be colored by the frass produced by the feeding activity of the borer. This photo shows boring dust on the lower part of the trunk, black crusty goo, and pupal cases left behind when moths emerged.

Figure 5: When you remove some of the crusty goo from the base of the tree you will often find clear goo underneath.

A peach tree damaged by this insect may take years to die.  The tree may die one branch at a time, or the whole tree may collapse over night.  The leaves on a limb with damaged roots may yellow one day and drop to the ground the next day.  The Fruit on a borer-infested tree will become dried up mummies.
Figure 6: Nutrient uptake is hampered by the feeding activity of the borer causing chlorosis as shown on the left side of this tree.

The Soil Drench Method

An insecticide drench with a relatively lengthy residual needs to be applied to the base of the tree in sufficient quantity to soak the ground. Since the entry point of this insect can be up to 8 inches above the soil line soaking the trunk to at least that height is important. Applications of carbaryl, permethrin, and esfenvalerate are recommended at the first of July and again at the beginning of August. If other products are used the length of time between applications will need to be adjusted based on the residual effect of the product. Do not apply these products within 14 days of harvest. When these sprays are missed, you can expect damage to your peach trees and other stone fruit trees and shrubs.

Para-dichlorobenzen (PDB)

Prior to 2009 the root systems of peach tree borer infested trees were fumigated using para-dichlorobenzene (PDB). This crystalline material is sold as moth balls and moth flakes. The crystals were placed in a shallow trench several inches out from the base of the tree or shrub and covered with a shallow layer of soil to contain the fumes. The fumes found their way through the goo to the borers feeding on the tree. This procedure was done in the fall when soil temperatures were above 50 degrees Fahrenheit. PDB can also damage plant tissue if placed directly against the bark of the tree. PDB did not replace the basal drenches recommended above but was a great way to clean up an infestation when a spray was missed or inadequate. PDB should not be confused with the moth balls and flakes containing naphthalene.

On October 31, 2006, Fertilome voluntarily requested US EPA terminate all uses of Fertilome Tree Borer Crystals. The product was registered for use on fruit trees but was no longer being produced in the United States. [2]

The Label is the Law

“Using a registered pesticide like mothballs against a pest not listed on the label is legal unless (1) the pesticide is used on a site not specified on the labeling or (2) the label specifically restricts the pests against which the pesticide may be used (e.g. “for use only against ants”). [3]

The container of Enoz Moth Ice Crystals I purchased on August 29, 2011, at the True Value Hardware store on Orchard Mesa does not specifically specify a site or restrict the products use against a specific pest. Based on the EPA statement at the beginning of this paragraph it appears this product can be legally used to fumigate the roots of peach tree borer infested trees.

Hand Worming

Hand worming is accomplished by removing the soil and goo around the base of the tree, finding the tunnels and pushing a flexible wire into the burrow to kill the borer. Hand worming is a major task especially when there are several hundred borer-infested trees to treat.

Mating Disruption

Some of the commercial peach orchards I walked this summer had globs of goo erupting from the soil at the base of their trees. Some growers have tried using pheromones to disrupt the mating flight of the moths and the reports are favorable as long as neighboring orchards are treated in the same manner. [4]


The use of insect parasitic nematodes such as Steinernema carpocapsae, S. feltiae, S. glaseri, Heterorhabditis heliothidis and H. bacteriophora are effective control options. The wrong type of soil, the wrong pH, chemicals in the soil, improper soil temperature, and many other factors affect the success of nematodes in their hunt for these borers.

A Quick Summary

Peach growers, whether backyard or commercial, will need to ensure they don’t miss the treatments necessary to control the peach tree borer, or they run the risk of losing their trees to this pest.





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