Cone & Seed Insects

Cone & Seed Insect Pests

Importance (really means economic threat ... $$)

~1/4 billion seedlings planted/year in BC

	but nurseries grow more seedlings (300-350 million) to account for culls
	need to sow even more seed (not 100% germination)

70-75% seed from wild stands / 25-30% from seed orchards

	seeds from seed orchards are expen$ive ... heavily managed ... (plus tree selection, grafting, fertilization, studies, etc)
	seed orchard trees are bred for favorable characteristics: fast growth, quality wood, resistance to insects & disease
	seeds from wild stands not nearly the same concern (just monitor to ensure collection efforts are not wasted)

insect losses can be significant (and therefore a concern)

	crops following a heavy cone crop are often heavily hit (and visa versa) - this makes sense to me
	BUT also some heavy cone crop years are heavily hit even if previous cone crop year was low ... hmmm ... let me think
	luckily only ~100 species of the 50,000+ known species in Canada are conophytes (cone/seed eaters)

Management Overview

Direct vs. Indirect Pests

direct pests lay eggs within the cone (between cone scales during flowering or within the seed when cone is 1/2 grown)

these pests are difficult to detect as they are inside the cone without feeding evidence

indirect pests lay eggs on the outside or near the cone

these pests are easier to detect as there will be entrance holes + frass

For wild seed collections ... primarily monitor cone crop just prior to collection to determine insect/ disease levels

For seed orchards it used to be set spray dates ... now ... IPM and breeding for resistant stock

IPM (the following describes how to minimize damage)

monitoring pests at all stages (flowering, conelets to mature cones)

consider history (previous year's crop size and damage level) & predicted crop size (a bumper year?)

ID pests

assess damage* (impact on seed production)

decide on treatment options (biological, mechanical, cultural, chemical - chemical difficult due to location of most seed orchards)

implement plan

monitor results (to provide improvements for future treatments)

* Assessment of impact on seed production (want a value that = actual / potential)

For each tree species: select a sample of trees (2-5%) and count ALL new cones (including dead & damaged) = pot'l seed crop

From this sample select a sub-sample of cones (~25) to monitor that season - and tag them

Assess cones 2-4 times during season (e.g. start of flowering, cone formation, 1/2 size cone, full-size cone) and assess damage level

Enter data into a pop'n prediction model to predict damage (and determine treatment option, as above under IPM)

Collect mature cones and extract/germinate seeds to determine actual seed production and compare with predictions (this way improvements can be made to pop'n model)

Facultative vs. Obligate Conophytes

	Facultative conophytes can feed on both cone/seed material and other material (i.e. can survive without cone/seeds)
	Obligate conophytes require cone/seed material to complete their life cycle, these critters are much more "in tune" with cone crops

Facultative

Obligate

dependency on cone/seed tissue

not dependent, mostly defoliators who enjoy a good meal of cone/seed tissue

dependent on cone/seed material

cone/seed material is ephemeral and periodic; can have bumper crops or "cone droughts"

therefore developed extended diapause

risk spreading or

predictive*

specificity (for host & tissue)

tend to be generalists (i.e. can utilize several host species and a variety of host tissue)

usually very specific to host & tissue, but sometimes specific to tissue (e.g. seeds) but a variety of hosts

population trends

cyclic but "stable"

"apparently unstable"

signs & symptoms

tend to be obvious (feeding activity and/or frass is readily apparent)

	often "hidden" as often eggs are deposited within the cone/seed
	sometimes need x-ray

reproduction

	not as picky about host or tissue
	often lay an egg mass

	very picky about host & tissue and are tuned into visual/chemical cues (tree form, bud colour/temp., volatiles)
	single eggs laid in very specific spots
	female often "scents" the egg site with "no vacancy" pheromone to ensure other eggs are not laid

* Extended Diapause - Risk Spreading vs. Predictive

	risk spreading - eggs are genetically programmed for diapause of various lengths (e.g. 30% in yr 1, 40% in yr 2, 30% in yr 3) - e.g. spruce cone moth obviously this spreads eggs hatching over various cone crops (bumper years & "droughts") and "spreads the risk"
	predictive - eggs are tied to the same cues as trees regarding cone crops - hatch when there is a bumper crop - e.g. Douglas-fir come moth

Selected Key Players

Unlike other "tissue feeders" (e.g. defoliators, bark beetles, etc.) where few insect orders are involved, several insect orders utilize cone/seed tissue - not a surprise when you consider the nutrition of the tissue

key orders are

	lepidoptera (40-45%) - some are generalists/facultative, others are specialists/obligate
	hemiptera (homoptera) (40-45%) - typically specialists/obligate [in BC ... w. conifer seed bug, a.k.a. the leaf-footed bug]
	hymenoptera (~10%) - specialists [seed chalsids]
	diptera (not many spp. in BC, but can be important)
	coleoptera
	thysanoptera (thrips)

selected examples

western (spruce) budworm [lepidoptera] is the most significant generalist that damages cones/seeds in BC

	grazes the the outside of cones - cones don't open
	plenty of s&s on outside (partially consumed cone, frass & webbing)

cone worms (Dyoryctia spp.) [lepidoptera] - damage apparent on the outside of the cone (large holes, frass & webbing) - tunnel inside the cone but push frass to the outside

cone moths (Barbara spp.) [lepidoptera] - damage can be apparent on the outside of small cones (less noticable on larger cones), larva feeds inside on cone scales & seeds, causes resin flow that prevents cone from opening when it matures

western conifer seed bug also the leaf-footed bug (Leptoglosis spp.) [hemiptera] - damage not apparent as the bug inserts stylet into cone to digest & suck up the seed contents

seed chalcids (Megastigmus spp.) [hymenoptera] can damage 10% of seeds in BC, but has been introduced into France and damage up to 100% of seed crop of Fd

cone gall midges (Contarinia spp.) [diptera] - is the main pest of Fd cone crops in BC, cones brown prematurely, galls inside (cone scales)

Images from Fetch21