Terminal Weevils ***biology

Question 1

Where do spruce terminal weevils overwinter and in what form

Answer 1

Over winters in the duff as an adult

Question 2

Where does weevil lay eggs?

Answer 2

Lays eggs on leader (terminal) in the bark.

Question 3

How long does it take for egg to mature to adult?

Answer 3

1 season. Adult lives for about 5 years relating the mating and egg laying cycle.

Lodgepole Pine weevil takes 2 seasons to mature

Question 4

What is the damage?

Answer 4

Kills leader (repeatedly in outbreaks)

Deformity

Growth loss ***

Avenue for decay

Question 5

Management

Answer 5

• hazard rating (warm climate helps weevil) weevil can’t build up in cold areas.

Survey

Short term: kill bug - Long term: happy healthy forest (plant brush space etc)

Tree breeding

Question 6

Hosts and range of terminal weevil ?

Answer 6

IWS aka white pine terminal beetle - most serious native pasts of spruce and pine regen *** 40% volume loss in bc

Range: across Canada, not in cold areas

Question 7

Where are spruce weevil a bigger problem?

Answer 7

Coast greater than interior

Warmer sites of vi and mainland bc

Question 8

What trees are most affected?

Answer 8

Spruce and Pine

Bc - Ss Sx

Size preference: 2-10m (1.5-20m)

Age preference 10-30y (5-40)

Attacks dominants with good leaders

Question 9

Are natural stands at risk?

Answer 9

Naturals at decreased risk because they do better underneath brush resulting in small leaders and wide spread stems.

Plantations at increased risk due to aggregation of food for weevil.

Question 10

How many years of growth are killed when the weevils attack?

Answer 10

2

Question 11

How far does the weevil typically travel

Answer 11

5m / yr

Question 12

How often do females need to mate?

How many eggs?

Answer 12

1

Feed to mature ovaries

About 100 eggs per leader. Fecal pellet laid on egg to protect it

Question 13

Why so many eggs per leader?

Answer 13

Need to be enough survivors to overcome tree defense

Question 14

Where do adults prefer to be on the tree?

Answer 14

Wherever the sun hits

Sleeps in duff

Question 15

What group does the terminal weevil belong to?

Answer 15

Coleoptera

Question 16

How do the different larval stages feed?

Answer 16

L1 feed independently

L2-L4 in a ring

Downward to food. Kills 2 yr growth

Question 17

How do larvae pupate?

Answer 17

Wood chip cocoons under bark

Question 18

When do adults emerge and what do they do?

Answer 18

Emerge in late summer and feed on laterals

Spring, fly to attack new tree

Question 19

What are some characteristics of the outbreak?***

Answer 19

Localized. When the stand is between 10-30 years and 2m-10m height the damage will be worst.

Question 20

What things can reduce an outbreak?

Answer 20

Competition, weather, PPP

Question 21

Why does outbreak decline after stand reaches 30-40

Answer 21

Once spruce is the dominant, it stops putting on fast growth and leaders are smaller

More effective resins produced as tree ages

Question 22

Pop dynamic

Answer 22

Attack starts at 5 yr

Stable peak from 10-30 years

Outbreak local

Higher intensity on better sites

Question 23

Susceptibility factors

Answer 23

Latitude, elevation and aspect (warmth)

Proximity to coast (maritime)

Question 24

Why can BEC zones be used as a weevil guide

Answer 24

Weevil conforms to climate. BEC reflects climate

Question 25

Stand preference based on *****

Answer 25

Host composition

2-10 m height 10-30 years age

Density (affects leader growth)

Crown closure and shading

Site productivity

Question 26

Mortality factors

Answer 26

• resin response to feeding and oviposition ( constituent and induced )

Competition (too many survivors will result in not enough food)

Question 27

PPP

Answer 27

Dipteran predators (not effective in outbreak)

Ground predation of sleeping adults by small mammals and other creatures

Question 28

What is key for larva survival

Answer 28

Weather

Poor litter quality can kill OW adult.

Question 29

Host selection ****

Answer 29

Beetle only lands on host spp (silhouette, chemical attractants, leader tip, needle density (less needles more sites), resin canal abundance, asses nutrient value)

Female attracted to tree, then attracts male.

Question 30

S and S

Answer 30

Resin droplets - feeding punctures *

Black fecal caps on egg sites *

Larva - white 1 cm grub under bark *

Exit holes if ur late

Shepherds crook

Question 31

Damage

Answer 31

10-40% reduction in merch volume

Avg 15-25

Dependant on: infestation level (20-40%) resident time (10-40 year)

Question 32

What are some results of terminal weevil?

Answer 32

Restricted use of SS on coast

Changing as resistant stock is becoming more available.