Jack Pine Budworm

Jack pine makes up a significant percentage of Manitoba's boreal coniferous forests. Jack pine budworm is a native insect to Manitoba that can cause significant damage to the trees, causing defoliation, growth loss, and even death.

It is believed that an outbreak of Jack pine budworm occurs in cycles of 8 to 10 years on average.

In 2015, moderate Jack pine defoliation was detected in Manitoba's northern Interlake area and determined to be the result of the budworm. Monitoring of the outbreak has determined that the population expanded in 2016 to almost 250, 000 hectares of moderate and severe defoliation See map

The last outbreak of Jack pine budworm in Manitoba was recorded in 1985.

Annual monitoring in the form of pheromone traps, aerial survey and branch sampling are used to gauge population levels.

Managing an outbreak

As budworm larvae can cause widespread defoliation, growth loss, top kill and tree mortality, it is important to help slow the spread and remove the affected trees as quickly as possible. One method that has proven effective is to harvest the infected trees and salvage the timber for use by local mills before the wood becomes unproductive. Salvage operations, such as the current approach taken in the northern Interlake area, help maximize the utilization of the forest resources while improving the overall health of the forest at the same time. If the trees are left unmanaged, the risk of the outbreak spreading to other healthy trees and the risk of wild fire become a more significant threat. Managing the impact to the forest in a planned way also helps to ensure we minimize the loss of critical wildlife habitat and help protect the natural beauty of our forests for recreation and tourism.

Areas that are being harvested as part of this treatment will be regenerated back to productive forest stands.

Treatment with insecticide is another method of managing an outbreak, however, the use of insecticide to treat a medium to large outbreak can be challenging. Before proceeding with a treatment of this nature, consideration would be given to effectiveness, costs and ecological risks. The current outbreak of Jack pine budworm is being monitored and insecticide treatment of the entire area is not currently recommended.

Biology-Life Cycle

The female moth lays its eggs through mid-July to early August. The eggs hatch in 7 to 10 days. The larvae emerge and spin a silken cover under bark scales or between pine needles.

The larvae emerge in late May and early June when the male cones of jack pine produce pollen. Young larvae feed initially on pollen. The majority then move to the new foliage when it is well developed. Needles are seldom consumed entirely but are often clipped at the base and webbed together. The accumulation of this feeding debris gives pine trees a scorched appearance in midsummer.

Feeding lasts approximately six weeks. Pupae develop among the needles or between webbed shoots from early to late July. Moths emerge in July and early August, mate and lay eggs. There is one generation per year.

Host species

Jack pine (Pinus banksiana) is the preferred host, but other conifers such as red pine (Pinus resinosa) and Scots pine (Pine sylvestris) can also be attacked.