Peach Tree Borers

Lesser Peach Tree Borer

Synanthedon pictipes (Grote & Robinson)

The peach tree borer complex is vital for the very tree’s existence, but it can present economically significant problems. Borers have a wide range of hosts that include all stone fruit trees as well as wild tree species (chock cherry, Amelancher sp., etc.). 

Biology 

The lesser peach tree borer (LPTB) is a clear-wing moth that overwinters as larvae in various stages of development. In the spring, larvae start feeding for a while then burrows into the outer bark of the tree, where it forms a cocoon in which it pupates. It takes between 20 and 30 days for the adult to emerge from its pupae. They are present in the orchard over several months, which makes the control difficult. 

Larvae are feeding within the inner bark or cambium layer of the tree trunk. Presence of gumming mixed in with wood shavings and frass around the wounds is a sure sign of their invasion. 

Figure 1. Injured trunk with signs of LPTB injury. Note gumming ooze mixed with frass and wood shavings. (Photo credit: M. Bulatovic-Danilovich)

Previously wounded parts of the tree are attractive to the borers, and they will enter the trees through those wounds. They are present near pruning wounds, valsa cankered areas, frost damaged trunks, etc. The lesser peach tree borer establishes itself only in tissue previously injured by some other cause, but never in healthy tissue (Figure 1).

The moths mate immediately after emergence with ovipositioning taking place in the first hour of their adult life. A female can deposit 500 to 600 eggs during her seven-day life span. Female moths deposit eggs in injured areas within 2.5 meters (8 feet) from the ground, predominantly at the levels of 80 to 120 cm (3 to 4 feet). At warmer temperatures, takes seven to 10 days for the eggs to hatch. Cooler temperatures may prolong incubation period to 15 days. Immediately, young larvae start borrowing into the surrounding tissue and starts feeding. If not discovered in time and not controlled, they can girdle the entire limb or trunk leading to die back. Borer injury also can lead to other opportunistic pathogens, like Cytospora/Valsa canker, bacterial canker and similar pathogens. 

In the northern states, the lesser peach tree borer adult moths are in flight from late May through September. In the north central states, peak emergence may occur from early June to mid-July, depending on the location. There is a single continuous generation each year; in years with hot temperatures, a partial second generation may occur. 

Control

The best control is by preventing tree injury. Perform pruning at the time that would ensure fast wounds healing. When mowing or performing other maintenance application, work carefully around trees not to injure trunks, limbs and branches. 

To help peach tree borer complex management, remove alternate hosts from the vicinity of the garden or orchard. 

Spraying to the point of runoff with systemic insecticide Chlorpyriphos (Lorsban 50 WP or 4E) to the trunks and lower scaffold limbs will control both, adults, and larvae. Timing for the first application is 10 to 14 days after the first adult emergence targeting just hatched larvae. Spray   with the handgun at low pressure at 100 pounds per square inch. 

Greater Peach Tree Borer 

Synanthedon exitiosa (Say)

Greater peach tree borer is a major pest in peaches and nectarines, but it also can be devastating the other stone fruit like cherries, plums and apricots.

Biology 

The greater peach tree borer is a clear-wing moth with a golden sheen on the wings. The body is metallic blue with a nice orange band across the abdomen of the female. 

The moth overwinters as larvae on or under the bark of trees, usually below the ground level. The larvae become active and begin to feed on the inner bark when the soil temperature reaches 50 F. When fully grown, the larvae construct cocoons and pupate, usually during late May and June. Moth emergence begins in early July and continues into September. The moths mate immediately after emerging and the female begins to lay eggs within 30 minutes with most eggs deposited the afternoon of the day of mating. The egg incubation period is from 10 to 15 days depending on the weather conditions. The young larvae bore into the bark at the base of the tree (Figure 2).  

Figure 2. GPTB Injury at the tree base – sap oozing with frass in it. Look for injury 2 to 3 inches under thesoil line. (Photo credit: M. Bulatovic-Danilovich)

Once beneath the bark, they feed on the cambium and inner bark of the tree tunneling 2 to 3 inches below the soil line. Normally, only one generation occurs each year in the north central states. Some larvae, however, may require two years to complete development. 

Larval feeding occurs 5 to 10 centimeters (2 to 4 inches) below the soil line. Larvae are cream colored with brown head caps, like the lesser peach tree borer except larger. Sometimes there are multiple larvae feeding on the same tree, girdling it fast and killing the tree. Greater peach tree borer finds injured trees and moves in where there is cracked bark on the trunk, canker wounds, black knot lesions on plums, etc. Besides the more attractive wounded areas, this pest can attack the healthy bark and start burrowing into it. 

Borer-infested trees usually have raised mound-like soil at the base of the trunk. Soil removal will expose the trunk below the soil line and a mass of gumming mixed in with frass, freshly made channels and even the main culprit, the larvae itself. 

Control

Trunk sprays with the handgun aimed to the young hatching larvae and adults. Timing will depend on the adult emergence and the weather conditions, about seven to 10 days after the first flight.

Commercial fruit growers have several materials available to use for successful management of this pest. Those include Thiodan 3 EC, Lorsban 4E and, to the lesser extent, Asana XL. Lorsban 4E is preferred formulation since it does have a longer residual effect.

Among other options to control both LPTB and GPTB besides Assana XL and Lorsban 4E areWarrior 1CS, Lmbada-Cy 1EC, Silencer 1EC, Warrior 2CS, Baythroid XL 1EC, Tombstone2EC, Mustang Maxx 0.8EC, Besiege and Danitol 2.4 EC. 

One material that homeowners can use in their gardens is Ortho Tree and Shrub Fruit Tree Spray – the active ingredient is a Pyrethrin, which is approved for organic use (chrysanthemum derivate). It is most effective when targeting adult moths.

There also are dispensers for pheromone mating disruption. The important fact is that the pheromone must be on trees before the adults emerge. ISOMATE has excellent efficacy. 

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