- Terminal Weevils - Mgmt
- Spruce Terminal Weevil - Mgmt
- Overview
- Site (hazard & risk)
- warmth
- richness
- Stand (silviculture)
- species
- density
- shading
- direct control
- breeding
- SEDA & JEM
-
- type "seda" in search box ...
- ... Stand Estab. Decision Aid
-
- Hazard Rating
- Methods
- Adjacent stands attacked
- Ecosystem
- these are MOF estimates
- Heat Sum
- what is it?
- accum. heat above a threshold temp
- units are 'degree days'
- calculation
- threshold temp for IWS = 7.2C
- HeatSum = ∑ Ave. Temp. - 7.2
- e.g. max=14.4 min=10.0 ... ave. = 12.2 ... 12.2 - 7.2 = 5.0 degree days
- days with a negative value are set to 0
- sum all the days in the year to get the degree days
- need climate data
- location / density of weather stn's?
- IWS values
- coast = 888 degree days
- interior = 785 degree days
- Other factors
- shading good
- rich soil bad
- open stand bad (<1200 sph)
- height 2-18m bad
- south-facing bad
- Prescription & Hazard
- Nil & Low - plant S with carefree abandon
- Med. - plant up to 20% S
- High - plant up to 10% S
- weevil resistant stock ... can plant more Ss (see Silviculture/Planting below)
- Silviculture
- Harvest
- clearcuts are warmest and favour IWS
- shading would be nice ... consider
- partial retention
- maintain non-merch if possible
- Planting
- S% as per hazard rating (above) unless ...
- improved "A" seed - then up to 50% S in M-H hazard
- naturally resistant "B+" seed - up to 30% in M-H hazard
- denser ~1,600 sph (vs. 1,000 - 1,200)
- mixed species
- pure S typical attack rates ~30%
- attack rates with mixed spp. ~15%
- in the interior ... "clump planting" with Pl
- Brushing
- why brush?
- eliminates competition for conifers
- increases survival & growth
- now larger leaders and less shade ... oops
- maintain some brush
- to provide shade, screening & smaller leaders
- but not too much
- reduced growth
- mechanical damage
- its a balancing act (brush vs weevil)
- simplistic view
- tall overstorey (At, Dr) - maybe brush and live with IWS damage
- short brush (willow) - maybe don't brush
- JS (Juvenile Spacing)
- dense stands ... less infection
- delay JS if
- high S%
- IWS present
- delay until pop'n declines
- Fertilize?
- well ... there is a study
- attacked increased
- but tree ht greater (even with attack)
- but wood quality not studied
- ... who knows??
- Rehab
- "mow it down" and convert to other species
-
- S required for min. stocking (i.e. NSR without S)
- current attack >30%
- unacceptable damage
- no other high resource value (=get out of jail free)
- Direct Control
- Leader Clipping
- labour intensive & $$$
- 2-3 x's / yr
- 5 consecutive years
- Insecticides
- "Forest Based" Stem Injection
- env safe
- gives 2 yr protection
- labour intensive
-
- spray leaders in spring
- spray just before emergence
- feeding on sprayed leaders kills adults
- no eggs laid
- insecticides:
- permethrins (synthetic version of pyrethrins ... mums)
- soil treatment
- soil drench with systemic insecticide
- "taken up" by tree
- weevil ingests insecticide
- a nicotine-based synthetic insecticide
- PPP
- pred: Lonchaea corticis (Dipt) shows most promise
- para: Eubazus (Hym: Braconidae) shows some promise
- egg-larval parasitoid
- needs to be introduced from Eurpoe
- issue: synchrony
- path: Microsporidia - fungal pathogen - not yet well studied on IWS
- Tree Breeding (Resistance)
- antixenosis (repellents & deterents)
- terpenes @ higher concentrations
- deters feeding & oviposition
- sclerid cell density
- tough, hard to digest
- damage digestive tract
- antibiosis
- juvenile hormone
- causes ovary atrophy
- no eggs laid
- resin
- kills eggs and/or larva before feeding ring
- breed for trees with higher density of resin canals
- resin types
- constituent resin
- traumatic resin - monoterpenes, better flow, soak egg site
- evasion
- phenology - less damage if buds burst before weevil attack
- Pine Terminal Weevil IWP
- Differences IWP vs. IWS
- H&R
- Pl (Pj)
- Interior (IDF, MS, ESSF)
- Biology
- eggs on newly emerging leader & feed UP
- OW in leader (higher mortality)
- 2-5m susc. ht. (not 2-10m)
- attack rate typically 5% (not 15-30%)
- Hazard
- ecosystem
- high - warm & dry (IDF)
- low - cool (ESSF) or wet (ICH)
- stand density
- high - at low density (<1400 sph)
- low - at high density (>2000 sph)
- stands spaced early
- increased leader growth
- attack concentrated on crop trees
- up to 66% attack
- ... this is a bad thing
- Mgmt
- plant mix species
- delay brushing until 5+m
- screening
- shade/ cooler
- smaller leaders
- if current attack >10%
- delay JS
- or leave denser stand ~2500 sph
- Last, explain why the IWP is ...
