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Lesser Peach Tree Borer - Is It Costing You Money?

General folk wisdom has suggested that lesser peach tree borer (LPTB) is more prominent in Essex and Kent counties, but there are areas with high borer pressure in Niagara as well. Lesser peach tree borer will take advantage of even the slightest injury on a tree to lay eggs which hatch into wood boring larvae. In some cases they may be causing economic damage through reduced production and shortened tree life.

Figure 1. Adult LPTB on sticky trap. A pretty picture of this clear- winged, day-flying moth would be nice, but you'll see the vast majority of them like this - in a mass of messy moths on a pheromone-baited sticky trap. Some training is required to identify these borers as other species may be attracted to the trap.

Figure 2. LPTB pupal case. When the moths emerge, their pupal case is often left behind stuck to the ooze on a canker.

Figure 3. LPTB larvae in peach canker (head buried in ooze). Digging around a bit in oozing cankers will sometimes yield one of these larvae. In highly infested sites, they are not hard to find. LPTB overwinter in the larval stage, but unlike many insects, this species can overwinter in 2nd all the way to mature 6th instar larvae. In the spring, some are nearly ready to pupate while others need to feed for several months before emerging - that's why there's such a long, continual flight period for this pest.

Figure 4. Frass (insect excrement) from feeding LPTB larvae can often be found in or around cankers. The frass is fairly obvious as pale brown granular material at the center of this picture. In many cases, it is mixed with ooze in cankers, but is still readily found with a bit of practice.

Figure 5. Young peach tree with LPTB infested canker. This young tree is otherwise healthy having received good care, timely pruning, and adequate irrigation and nutrition. However, with LPTB-infested peach canker at this part of the trunk, its lifespan will be shortened. It seems to be producing well now, but will decline faster than it should.

There are a few management recommendations for this pest. Trees should be dipped in thiodan (endosulfan) mix before planting and trunk and lower scaffold limb sprays are recommended in the early years, especially where LPTB pressure is known to be high. There is no threshold based on trap captures or anything else to help time the sprays in this case. LPTB started flying in Niagara this year on May 24 and their flight will continue until late August or early September. Up to three sprays can be applied, but care must be taken with anticipated harvest of early varieties as endosulfan products have relatively long pre-harvest intervals. Direct these applications away from fruit - LPTB is completely uninterested in fruit anyway.

Regular monitoring to look for signs of the pest is also important - even where you don't think you have a problem. Finding this pest early before it has become common in an orchard makes dealing with it much easier and less costly.

Mating disruption (MD) of this moth is possible with a product called "Isomate-P" which is registered and available in Ontario. Like all MD products, it works best when applied before first flight and on large areas. In heavily infested areas, a combination of pesticides and MD may be needed to help lower the population over a few years.