Defoliators

Question 1

What is the prime order of defoliators?

Answer 1

Liepidoptera

Complete metamorphosis

Question 2

How do most defoliators over winter?

Answer 2

Egg

But some like SS tiger moth and WS budworm ow as larva

Question 3

How are defoliators commonly categorized?

Answer 3

By tissue: (chewers, skeletonizers, miners, suckers)

By age: (new, new and old, old)

By host specificity (mono (specific), oligo (family specific), polyphagous (any thing))

Question 4

How do insect disturbance differ from abiotic?

Answer 4

Insects are Spatially synchronized and temporally periodic due to optimal weather conditions.

Question 5

2 other pests of interest due to climate

Answer 5

Fd tussock moth - young and old foliage. Kills tree

Spruce budworm - attacks buds and new foliage. Typically doesn’t off tree but reduce growth.

Question 6

Dougs favourite defoliators

Answer 6

Western spruce budworm, Fd tussock moth, gypsy moth

Question 7

4 population stages of an outbreak

Answer 7

Endemic, building, epidemic, collapse

Question 8

What determines defoliators population?

Answer 8

Host abundance

Weather (temp and precipitation)

Natural enemies

Question 9

What is the # 1 category for damage in North America?

Answer 9

Defoliators

Question 10

What is the most effective time to kill caterpillars with pesticide?

Answer 10

Late in the year when they are their largest. Sacrifices a year of growth.

Question 11

What is the best time for foliage protection?

Answer 11

Early in the season. Kills some but not all caterpillars, but drastically reduces defoliation damage. Might have to spray again next year.

Question 12

How often does Fd Tussock moth go into outbreak? How long is the outbreak and why?

Answer 12

Once every 10 or so years. Lasts about 2 years until crash. Crashes due to BTK and NPV (virus pathogens).

Question 13

Why is BTK such an effective selective tool? What is the downside?

Answer 13

Species specific to caterpillars. Won’t harm non pest creatures but could kill other butterfly species that are beneficial.

Question 14

Is severity of defoliators attack uniform?

Answer 14

No, intensity varies from high to low, with only about 10% in the high level. These areas are defined during annual surveys.

Question 15

How might climate change effect the severity, timing and duration of outbreaks?

Answer 15

All 3 will increase as a result of warmer weather.

Question 16

Why does the WS budworm target the tops of trees for egg laying?

Answer 16

Because it gives the caterpillar the option to easily repel down to fresh foliage as opposed to trying to climb up.

Question 17

Are dominant or intermediate trees more likely to die from defoliation?

Answer 17

Intermediate. Adds an extra element to planning if you want to use intermediate trees to reforest site when you remove the dominants.

Question 18

Out of conifers and deciduous, which has more energy invested in foliage protection?

Answer 18

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.

Question 19

Why are deciduous less damaged by defoliators?

Answer 19

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.

Question 20

How many years can WS budworm outbreaks last?

Answer 20

Up to 9 years

Question 21

How are outbreaks quantified?

Answer 21

By longevity and severity.

Question 22

As far as defoliation hazard goes, what metrics increase hazard to high

Answer 22

• 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.

Question 23

What are host defenses?

Answer 23

• 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.