Jack pine budworm

Overview

• Native to North America.
• Jack pine budworm is a native insect that periodically reaches outbreak levels (approximately every 8-10 years) in Ontario.
• The budworm larvae cause widespread defoliation, growth loss, top kill and tree mortality.

Host species

Jack pine (Pinus banksiana) is the preferred host, but other conifers such as eastern white pine (i>Pinus strobus), red pine (Pinus resinosa) and Scots pine (Pinus sylvestris) can also be attacked. In some cases, the budworm has maintained outbreak populations and caused severe defoliation in white pine stands.

Species identification and life cycle

• Larvae (2^nd instar) emerge from under bark scales in late May or early June.
• Larvae begin feeding in the male pollen flowers and then move on to developing needles of new shoots.
• The majority of feeding is done in late June and early July.
• Mature larvae are 21mm long, have reddish-brown heads, reddish-brown body with yellowish sides and two rows of white dots on their back.
• Pupation occurs on the shoot or among the needles in July to early August.
• The tawny brown moth with a wing-span of 15-24 mm emerges in mid-late July to early August.
• Eggs are laid on needles in masses of two or three overlapping rows.
• Eggs hatch within 10 days and the tiny larvae find protected areas under the bark where they spend the winter protected in a silken web called a hibernacula.

Symptoms and damage

• Larvae (caterpillars) feed on the needles and male pollen flowers.
• Partially-chewed needles by the larvae and the accumulated spun silk, can give the attacked trees a reddish-brown appearance.
• Defoliation can lead to widespread discolouration and browning of foliage throughout the forest.
• All the needles in the upper crown may be consumed, while some foliage may remain in part of the tree.
• Defoliation is often most severe in the first year it is detected, which can result in growth loss, top kill and tree mortality; during infestations, multiple years of moderate-severe defoliation can cause whole tree mortality in as little as 2 to 3 years.

Control measures

During severe outbreaks, the bacterial spray Bacillus thuringiensis kurstaki (Btk) can be applied to highly valued stands.