Defoliators Flashcards
What is the prime order of defoliators?
Liepidoptera
Complete metamorphosis
How do most defoliators over winter?
Egg
But some like SS tiger moth and WS budworm ow as larva
How are defoliators commonly categorized?
By tissue: (chewers, skeletonizers, miners, suckers)
By age: (new, new and old, old)
By host specificity (mono (specific), oligo (family specific), polyphagous (any thing))
How do insect disturbance differ from abiotic?
Insects are Spatially synchronized and temporally periodic due to optimal weather conditions.
2 other pests of interest due to climate
Fd tussock moth - young and old foliage. Kills tree
Spruce budworm - attacks buds and new foliage. Typically doesn’t off tree but reduce growth.
Dougs favourite defoliators
Western spruce budworm, Fd tussock moth, gypsy moth
4 population stages of an outbreak
Endemic, building, epidemic, collapse
What determines defoliators population?
Host abundance
Weather (temp and precipitation)
Natural enemies
What is the # 1 category for damage in North America?
Defoliators
What is the most effective time to kill caterpillars with pesticide?
Late in the year when they are their largest. Sacrifices a year of growth.
What is the best time for foliage protection?
Early in the season. Kills some but not all caterpillars, but drastically reduces defoliation damage. Might have to spray again next year.
How often does Fd Tussock moth go into outbreak? How long is the outbreak and why?
Once every 10 or so years. Lasts about 2 years until crash. Crashes due to BTK and NPV (virus pathogens).
Why is BTK such an effective selective tool? What is the downside?
Species specific to caterpillars. Won’t harm non pest creatures but could kill other butterfly species that are beneficial.
Is severity of defoliators attack uniform?
No, intensity varies from high to low, with only about 10% in the high level. These areas are defined during annual surveys.
How might climate change effect the severity, timing and duration of outbreaks?
All 3 will increase as a result of warmer weather.
Why does the WS budworm target the tops of trees for egg laying?
Because it gives the caterpillar the option to easily repel down to fresh foliage as opposed to trying to climb up.
Are dominant or intermediate trees more likely to die from defoliation?
Intermediate. Adds an extra element to planning if you want to use intermediate trees to reforest site when you remove the dominants.
Out of conifers and deciduous, which has more energy invested in foliage protection?
Conifers, create natural defenses that require co-evolution of insects in order for them to attack. That is why many insect pests are host specific.
Why are deciduous less damaged by defoliators?
Can produce leaves more often, even in the period of a growing season following defoliation. Leaves cost less energy and are replaced yearly wheras conifer needles are energy intensive and designed to last for 3-7 years.
Also, conifers store most carbs in the foliage wheras deciduous store carbs in the roots.
How many years can WS budworm outbreaks last?
Up to 9 years
How are outbreaks quantified?
By longevity and severity.
As far as defoliation hazard goes, what metrics increase hazard to high
- warm and dry sites
- greater than 80% Fd, more host more bad.
- high density creates higher hazard
- more mature, higher hazard
- selective harvest is a higher hazard because it creates more immature trees that are susceptible to mortality by defoliation.
What are host defenses?
- Asynchrony of bud burst and egg hatch (luck)
- tolerance/resilience (just like ppl)
- compensatory growth: Deciduous can use carb reserves for photosynthesis. Some conifers will produce a longer needle in the year after defoliation.
- needle toughness and nutrient content
- Antibiotics/ deterrents (constituent (built in) and induced (reactional).
- Having more deciduous species around will provide alternate food with low defences for defoliators
- volatiles and chemical signals between species. Alerts other trees to danger and Also calls parasitoids.
