Budworms Flashcards
Family
Torticidae (leaf rollers and fruit worms)
Lepidoptera
Western spruce and (eastern) spruce budworm
Most common conifer defoliators in Notth America
Western Pine budworm and jack pine budworm
Spruce budworm Host
Lots of Balsam Fir! but defoliates all trees
Likes white spruce and red
Occasionally: black/blue spruce, hemlock, white pine, tamarack when within close proximity to balsam fir
Jack pine budworm host
Jack pine and red pine sometimes
Budworm damage indicators
Male pollen cones will be mined out
Prefers older trees with more pollen cones
Prefer to eat new needles
Webbing and webbing shoots
Frass
Mined shoots
Messy feeders: dist. From sawfly by their scattered, missing/severed needles often stuck in webbing
Damaged species look orange from a distance. (Damaged needles staying to decompose in webbing)
Host impacts from budworms
Top kill (after 2-3 years of defoliation)
-larvae and females attracted to light
-reduced/stunted growth and flower production
-death/mortality of balsam fir after 3-5 consecutive years of heavy defoliation
-2-3 for jack pine
Lifecycle
Hibernacula: overwintering larvae will mine buds or older needles slightly before budbreak in spring
Shortly after emergence, tiny larvae with black heads and no other markings (creamy, no stripes)
6th instar caterpillars with dark head and hard shield with greenish body color and 2 white spots on either side of “spine”
-up to 1 inch
Pupae in early summer; pupae cases persist well into fall
Bell shaped, 0.75 inch wide wingspan, brown-gray mottled moths in summer
Egg mazes in summer (mid-late July); hatched masses disperse and spin hibernacula where they molt into 2nd instar for overwintering
Budworm lookalikes
Yellow headed spruce sawfly: no webbing/silk, very thorough feeders on spruce (clean their plate), larvae have 6 or more prolegs
Balsam Fir sawfly: no webbing, prefers old needles (leaves newer needles), 6 or more prolegs
Red headed pine sawfly: thorough defoliation (old needles first), favors young trees, 6 or more prolegs
Spruce needle miner: many mined needles tightly webbed/adhered to shoot in a more artistic fashion, greenish bodied larvae, main host is spruce
2 surveys to predict level of defoliation
1) early larval 3rd-4th instar survey to predict jack pine budworm
-survey will pollen cones soften
-count larvae in 15 pollen shoots and 15 vegetative shoots per stand
->20 large per 30 shoots = moderate to heavy defoliation esp with higher amts of pollen cones
2) egg mass survey
-survey in late July/august (make sure most pupal cases are empty)
-prune off 3 mid canopy branches
-count egg masses on last 15 foliages inches of each branch
->1.0-1.8 egg masses / branch = severe defoliation (unless parasitized eggs!)
*used to detect areas of defoliation for mature trees that want to be saved (could spray aerial insecticide ((BTK)) for mature trees that are expected to be defoliated)
Budworm Outbreaks
Jack pine Last about 4 years, bc that’s how long the tree can survive
Spruce budworm about 8 years “ “
Once tree dies, budworms lose their food source and die
Management
Monitoring: multi-year defoliation. Pre-salvage; reduce fuels for wildfire; replant
Diversify forests (age and species) across landscapes and within stands
Thin spruce plantations (not during outbreaks)
Reduce percentage of balsam fir
Lower rotation ages
-<50 for some spruce-fir stands
Ornamentals and forests: spray btk when spruce needles are about 1/2 inch long
