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Budworms

Characteristics:

  • Eggs: Egg masses are laid in June & early July on underside of needles of evergreen trees. Each mass contains about 20 light green eggs. The eggs hatch in 10 days.
  • Larvae: Newly-hatched larvae are 2 mm long and appear yellow-green in colour eventually changing to dark brown. Larvae go through 5 “instars” as they grow, moving to a new location in the tree each time and making new shelters.
  • First instar: Larvae appear and spin silken shelters in cracks and on twigs where they moult.
  • Second instar: Larvae wait in silken shelter until following spring.
  • Third instar: Larvae emerge from silken shelter in May to begin feeding on needle buds.
  • Fourth instar: As they continue growing, the budworms forms a protective shelter of silk webbing, bud scales, and debris where they are feeding.
  • Fifth instar: In the latter half of June, the worm enters the shelter and begins pupation.
  • Adult: Adults are small grey-brown moths appear 10 days after pupation. They are approximately 13 mm long.

Identifying infestations:

  • Brown tips on evergreen trees The budworm causes evergreen needles and tips to turn reddish-brown in May and June as worms feed. Trees most likely to be infected include: White Spruce, Colorado Spruce, Pine, and Larch trees.
  • Defoliation If the infestation is severe, a new growth will be destroyed and old growth may be defoliated. Severe infestations lasting 3 to 5 years can result in dieback.

IPM Toolkit:

  • Preventive tools: Not applicable
  • Physical tools: Not applicable
  • Biological tools: Not applicable
  • Chemical tools: Use an organic insecticide called Bacillus thuringensis var. kurstaki (Bt.k.) Apply directly to infested areas according to label directions.