FINAL REVIEW: Three Defoliators Info

Question 1

Douglas Fir Tussock Moth: Distribution and Hosts

Answer 1

• Distribution: Dry IDF and PP & Kamloops Region
• Hosts: Primary: Fd

Secondary: Abies spp, Py

Occasionally Lw

Question 9

Difference between eruptive and chronic long term defoliators and examples of each

Answer 9

• Eruptive: Arise rapidly and can cause most damage/mortality in first year or two of outbreak (Eg: douglas fir tussock moth; False hemlock looper; western hemlock looper)
• Chronic Long term: Can arise gradually or rapidly; Impacts usually occur after a few consecutive years of defoliation

Question 10

Fd Tussock Moth: Population Dynamics

Answer 10

• oubreaks start small, localized, and turn into big areas
• low elevation stands only
• building phase of outbreak takes 1-2 years
• early detection important(during building phase)or else significant damage can occur-same as MPB
• High population levels for 1-4 years, then collapse due to: natural control agents; starvation due to forced consumption of less than adequate foliage; species specific nucleopolyhedrosis virus(always present in pops with low levels)
• Takes 6-8 years for populations to get to damaging levels again

**Refer to handout for relative risk assessment**

Question 11

Fd Tussock Moth: Damage

Answer 11

• Eruptive defoliator
• Larvae eat new and old foliage
• Top third of stem is defoliated first
• Attacks all age classes in the stand
• Mortality can occur after 2-3 years of severe attack(1 year not enough to cause mortality)

Question 12

Fd Tussock Moth: Mgmt strategies(long and short term)

Answer 12

Long Term:

• course of action should match long term SMO’s
• Stand manipulation tactics: conversion to alternate species; promotion of species mixes; stand structure manipulation (harvesting, thinning)

Short Term:

• Careful monitoring of populations in high hazard stands during non outbreak and building phases
• Aerial treatment using NPV for early treatment of incipient outbreaks a year before significant defoliation expected (will cause population to collapse and no further treatment will be required)
• once outbreak begins, options are limited-once you’re beyond first year, not worth it to apply treatments

Question 13

Western Hemlock Looper: Distribution and Hosts

Answer 13

• Coast and Interior wet belts
• Van region and East Central Interior(Revelstoke)
• Mature and overmature Hw/Cw stands targeted, though can also target younger 80-100 year old stands during outbreaks
• Prefers Hw
• Chews on almost any foliage during oubreaks, including deciduous

Question 14

Western Hemlock Looper: Population Dynamics and Detection

Answer 14

• Reaches outbreak levels every 11 years on coast and 20+years in interior
• outbreaks usually last 3 years, usually brought under control after that by parasites, predators and diseases
• trees could be stripped in single season during heavy infestation
• defoliation starts in upper crown, as feeding progresses more and more of the crown is affected, increasing the risk of mortality
• eat all the best foliage first, not enough good material left by the time populations explode
• wasteful feeders-chew at base of needle
• heavy rains reduces egg laying

Question 15

western hemlock looper: Life cycle

Answer 15

• larvae hatch from eggs in spring
• may -july feeding by early instars is light
• mid july-oct growing larvae feed more on both new and old foliage
• very mobile in late summer
• ground littered with parts of needles, frass, thousands of dead moths by fall

Question 16

Western Hemlock Looper: Damage

Answer 16

• Eruptive defoliator
• Mortality estimates for interior attacks: Light defoliation (less than 25%) results in mortality of less than 15%; Severe defoliation of greater than 65% results in mortality of greater than 50%

Question 17

Western Hemlock Looper: management

Answer 17

Long Term

• Promoting following types of stands will reduce susceptibility:well spaced, even aged, health and managed, early rotation, mixed stands with less than 50% Hw

Short Term

• BTK bacterial insecticide spraying can be effective only if deployed in conjunction with effective ID and monitoring of susceptible stands

Question 18

Western Spruce Budworm Distribution and Hosts

Answer 18

Distribution: Coast and BC SI, IDF, Dry CWH, some ICH (leans more towards hotter, drier zones)

HOsts: Primarily Fd; Abies spp

Question 19

Western Spruce Budworm Population Dynamics

Answer 19

• climate and weather influence outbreaks
• leads to unpredicatable and irregular fluctuations
• in chronically affected stands, outbreaks could be sustained for more than 25 years
• natural mortality factors: parasites, predators, pathogens, starvation
• 2nd instar of life cycle critical to survival
• Estimate risk by combining historical occurrence of outbreaks with stand parameters influencing hazard

Question 20

Western Spruce Budworm damage

Answer 20

• Chronic, long term defoliator
• larval feeding causes damage to buds, cones, new foliage
• upper crowns affected first
• larvae back feed on old foliage when populations are high, causes significant damage in one growing season
• larval migration from overstorey trees cause intense damage to understorey trees in multi layered stands
• attacks result in: increment loss, top kill, mortality of suppressed and intermediate, high susceptibility to mortality of advanced regen

Question 21

western spruce budworm mgmt strategies

Answer 21

Long term:

• Promoting following types of stands reduces susceptibility:
  alternative species and species mixes; even aged mosaics; stand structure manipulation; stand improvement

Short Term:

• BTK spraying effective only if deployed in conjunction with effective ID and monitoring of susceptible stands (should coincide with peak 4th or 5th instar)