Lilac-Ash Borer
Pest Common Name
- Lilac-Ash Borer (Podosesia syringae)
- All adapted Fraxinus tree species, including:
- Green ash (Fraxinus pennsyvanica)
- White ash (Fraxinus americana)
- Blue ash (Fraxinum quadrangulata)
- European common ash (Fraxinus excelcior)
- Black ash (Fraxinus nigra)
- Lilacs (Syringa sp.)
- Privet (Ligustrum sp.)
The lilac-ash borer is a one-inch (2.54 cm) long lepidopteran clearwing moth. However, body morphology and markings (orange and yellowish markings on a black body) are reminiscent of a paper wasp (Figures 1-3).
Biology
The larval stage of this insect is the damaging phase. Adult females lay eggs on the cracks, crevices and damaged areas of the bark. Eggs hatch and enter the bark of the tree, foraging under the bark and damaging the phloem tissue. Injury to ash trees is not limited to the physical damage the insect does; borer holes are also entry points for turkey-tail fungus (Trametes versicolor), which can further damage plants.
Adult lilac-ash borer moths emerge in spring from a round exit hole bored from the inside at the top of their gallery (Figure 4). They mate, and within a few hours, lay eggs (usually at the base of major branches) and the young larvae tunnel under the bark. After a summer spent feeding under the bark tissue (cambium layer), the larvae migrate toward the heartwood where they spend the winter. In spring, fully grown larvae tunnel partially out through the bark and then complete pupation. As the adult moth emerges, the pupal shell often remains mostly intact and protrudes from the hole. Sometimes this is barely noticeable, but commonly the pupal case protrudes about one-half inch (1.27 cm). In 幸运快三, lilac-ash borers complete one life cycle per year.
Damage
Affected trees (Figure 5) may show a rapid or slow progression of injury symptoms, including
- Loosened or separating bark
- Branch dieback
- Weakened branches that become susceptible to wind breakage
Diagnostic plant symptoms caused by lilac-ash borer include
- Extensive feeding galleries in the cambial layer underneath the bark
- Loose or damaged bark, especially around the base of large structural branches
- Wilting and chlorotic leaves at the ends of damaged branches
- Dead or dying branches scattered among healthy branches of the infested tree
- Weak branches that may result in random fall events or wind breakage
