- Defoliators
- Overview
- #1 NA, #2 BC
- "aggressive"
- appear suddenly
- damage - growth loss (predisposition, mortality)
- feeding period is short (4-8 weeks), most time in dormant state
- generalized life cycle
- moths / butterflies - sex, eating (may be optional)
- eggs
- larva - eating machines
- pupa
- OW stage varies btwn spp
- eggs - tussock moths, loopers, tent caterpillars
- larvae - spruce budworms, silver-spotted tiger moth
- pupae - some sawflies
- adults - rare, mourning cloak
- 'big players'
- western (spruce) budworm IDW
- biggest defol. in BC
- eats Fd
- interior of BC (OK, Fraser Canyon)
- budworm ... outside of crown
- spins down - lower crown & intermediates heavily defoliated
- spray Btk (carbaryl)
- Douglas-fir tussock moth IDT
- probably #2
- eats Fd
- interior BC - "cow country"
- can kill trees, top kill common
- spray Btk or NPV
- trap to monitor
- mating disruption - pheromones
- black-headed budworm IDH
- BC: coastal (CWH) & interior wetbelt (ICH)
- HB stands
- outbreak every 10-15 years
- often with hemlock sawfly (attacks older foliage)
- western hemlock looper IDL
- BC: coastal (CWH) & interior wetbelt (ICH)
- H (C)
- typically near water (shorelines, creeks)
- wasteful feeders - can kill if prolonged outbreak (3-4 yrs)
- forest tent caterpillar IDF
- gypsy moth IDM
- introduced, now estab. in e NA
- get periodic introductions in w NA
- eats 30+ spp (deciduous)
- forestry problem?? only for trade
- MOF has spray expertise ...
- video clips
- Defoliator Categories
- by tissue
- leaf chewers (some efficient, others wasteful)
- skeltonizers
- leaf miners
- leaf suckers - aphids
- by tissue age
- new (budworms)
- old & new (Douglas-fir tussock moth & w. hemlock looper)
- by host specificity
- many hosts - IDM
- few hosts - IDW
- single host - larch case bearer
- Outbreaks
- timing btwn outbreaks
- sporatic - triggered by env cues, temp.
- periodic - regular return intervals - IDT every 9-10 yrs
- 4 stages
- endemic - 'usual level'
- building phase - hard to detect (50%), last 2-3 yrs
- epidemic - peak damage, easy to notice, lasts 3-4+ yrs
- collapse - 3P's, weather, food; 1-2 yrs
- distribution vs. pattern
- distrib'n = geog. range (historic outbreak areas vs "just being there")
- pattern = where on the landscape
- elev bands IDW
- close to water IDL
- severity of outbreak ("how much" or "how big")
- intensity
- nil
- light - branch tip/ upper crown, barely visible from air
- mod. - top 1/3 severely defol., noticably thin crown
- severe - bare branch tips, top completely defol., >50% defol.
- extents
- where
- map of current outbreak
- map (photo) showing both
- Damage & Recovery
- conifer vs. deciduous
- decid better able to recover
- re-leaf midseason
- leaf designed for months not years
- conifers rely on foliage
- photosynthesis for several years
- storage of carbohydrates
- dominant vs intermediate
- dom. better able to recover
- vigorous - better energy reserves
- defol. often progress top - down
- time of year (conifer) - early vs. late in season
- earlier a problem if buds destroyed
- later in season buds formed and not attacked
- longevity of outbreak
- conifers can withstand 1 yr complete defol or several yrs of partial
- decid can withstand ~3 yr complete defol
- Impacts
- ↓ foliage, ↓ photosynthesis, ↓ growth, ↓ vigour
- predisposition/ stress
- can lead to 'complexes' with root disease and or bark beetles
- top kill
- avenue for decay entry
- deformity
- cone/seed loss
- mortality (IDM, IDT, IDL, IDH)
- non-timber impacts
- aesthetics & recreation
- thinner crowns
- ↑ light to ground, ↑ vegetation, ↑ summer forage
- ↓ thermal cover, ↓ snow interception
- human health - allergic reactions (IDT)
- watershed processes - less ET, more water in system
- trade embargoes (IDM)
- Monitoring / Detection
- Annual Overview Survey
- Aerial Survey
- summer
- 1:100,000 sketch maps
- "low intensity but great extents" ...
- ... may trigger follow-up ground surveys
- Ground Survey (walk-through)
- in areas noted in air survey
- esp. in building/ collapse phases
- target high hazard areas
- confirm pest ID and intensity
- Intensive Surveys
- Predictive - forecast NEXT yr's pop'n
- adults in summer with traps
- eggs in late summer/fall
- L2 - IDW, $$, only if problem & egg survey not done
- Population - THIS yr's pop'n
- pre-treatment - confirm forecast from predictive survey
- post-treatment - assess efficacy of trtmt
- Mgmt Strategies
- Long Term
- Monitoring - annual surveys
- tree species variety within stand and over landscape
- varied age classes over landscape (distribute harvesting)
- open stand stucture (esp. Fd for IDW)
- maintain stand vigour - density (fert.?)
- biodiversity (WTP & snags for the pretty birdies)
- maintain a research program
- Short Term
- monitoring - predictive/ pop'n
- spray insecticides (chem. or bio)
- foliage (tree) protection
- protect this yr's foliage
- apply early in season before much defol.
- not as effective for pop'n control
- moth re-invasion likely
- typically done later in outbreak
- trees have suffered successive years of defoliation ...
- ... and cannot handle another year of needle loss ...
- ... so foliage protection is more important than kill rate
- BTK often used
- how it works - image
- Btk - comprised of crystal (toxin) + spore
- needs to be eaten by larva
- requires alkaline gut and specific enzyme (only in caterpillars
- crystal dissolves, releases toxin, paralyzes gut, stop feeding
- MOF site
- Health Canada
- pop'n control
- 'kill the bug'
- apply Btk later in season
- better kill rate
- but more defol.
- so it's done earlier in the outbreak (yr 1 or 2)
- before trees have suffered much damage
- or ...NPV a good choice
- how it works - image
- liquified larva - yuck
- crystals with virus get ingested, virus gets released, takes over cells & replicates
- larva stops feeding & turns to mush
- very host specific
- high mortality rate
- but takes 5-8 weeks for the kill (not good for fol. prot.)
- can persist to next generation
- good for a "new" infestation - not much damage yet
- mating disruption
- spray attractant pheromones
- confuse the males (not that hard to do)
- cannot find mates
- "2nd chance" if pesticides don't work
- used for IDT
