Whitespotted Sawyer Beetle

Whitespotted Sawyer Beetle, (Monochamus scutellatus) eastern white pine is preferred, but other conifers including red and jack pine, alsam fir, larch, white, black and red spruces are also susceptible.

Adult beetles are 18–25 mm long. Males are shiny black except for a small, round, white spot at the base of the elytra. Females may have mottled white spots on the elytra. Larvae are creamy-white grubs, 35–50 mm long when full grown, with a yellowish thorax and brown head.

The whitespotted sawyer is a bronzy black, while the Asian longhorned beetle is true black and shiny.

Life Cycle: There is a one or two years are required to complete in generation life cycle. Mating generally occurs in the afternoons of warm, sunny days, on or near the host. Shortly after mating, the female chews long slits or niches in the bark of the host, preferably near old branch scars or wrinkled areas Adults emerge between late May and August through circular holes 8–11 mm in diameter, and feed on needles and tender bark. Adults emerge through circular exit holes in the wood and are present during the summer.

They feed on tender bark of twigs, causing tips to flag. Eggs are laid in the bark crevices of weak, recently-killed or newly-cut trees. When eggs hatch, young larvae bore a tunnel through the phloem into the cambium. Young larvae mine beneath the bark. Later instars tunnel toward the heartwood. Prior to pupation, the larva turns its tunnel toward the surface, where it pupates behind a chip plug.

Eggs are laid in chewed bark slits. Young larvae enter the tree through oval shaped holes in the bark and feed on inner bark, cambium and outer sapwood, excavating surface galleries that they fill with frass.

Damage: This beetle damages urban trees when the adult beetles feed on bark on the underside of twigs, causing the tips to die and turn red. The beetle damages, larvae mine first in the surface, layers of the wood, then into the inner layers. Their mines open the way for wood-destroying fungi. The larvae tunnel into the wood and degrade the value of lumber.

The borings in a heavily infested pulpstick may decrease the wood volume up to 5 percent. This loss is compounded by discoloration of the wood and the presence of soft, punky sap rot from the associated fungi. Pine wood nematode and the damage caused to a pine tree.

Control: Trees infected be felled and the wood destroyed as soon as possible. Trunks should also be removed. If the softwood is to be used for burning in fireplaces, etc., the bark should be removed or avoid harvesting the wood when sawyer beetles are laying eggs July to September. The most effective method is to avoid planting non-native pine species in areas where the average summer temperature exceeds 20ºC.

Where these non-native pines already exist, care should be taken to water and fertilize them properly especially during periods of drought. Many studies have indicated a positive correlation between temperature and trees exhibiting pine wilt. The higher the average temperature, the greater the number of infected trees. chemical applied to rough wood in the field is also a feasible means of reducing borer damage.