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Insect Pests on Trees & Shrubs

Aphid
Apple Maggot 
Ash Bark Beetle
Ash Leaf Cone Caterpillar
Ash Plant Bug 
Birchleaf Miner
Boxelder Midge
Cankerworm
Cottony Psyllid 
Dogwood Sawfly
Dusky Birch Sawfly
Elm Leaf Miner
Elm Scale
Erineum Gall Mite (Velvet Mite)

 

Europhid Mite on Cranberry
Europhid Mite on Maple
Hawthorn Lace Bug
Leaf Cutter Bee
Leaf Hopper
Leaf Rollers on Aspen
Leaf Tiers on Aspen
Lilac Leaf Miner
Maple Leafcutter Moth
Microscopic Mites
Oak Gall
Oak Gall Wasp
Oak Mite
Oak Phylloxera Aphid

Pear Slug
Poplar Borer
Poplar Willow Borer
Scurfy Scale
Slugs
Spider Mites
Stink Bug
Tent Caterpillar
Thrip
Viburnum Leaf Beetle
White Pine Weevil
Willow Leaf Blotch Miner
Wooly Bear


 
 
 
 
 
 
Aphids

Plants Affected - Numerous

Symptoms - Severe infestations will cause curling/twisting of foliage, flowers to wilt and drop.

Controls - Cultural or Non-chemical:
• Ladybird beetles/larvae, lacewings are natural predators.
• Strong jet of water to knock aphids off plants.

Controls - Chemical:
• Insecticidal soap, Doktor Doom House and Garden, and various other insecticides.


 
 
 
 
 
 
Apple Maggot

Plants Affected - Apple, Evans Cherry, Hawthorn.  Worse on early ripening apples.

Symptoms - Life Cycle
• Adults lay eggs in fruit early to mid July. Maggots make trails rendering fruit inedible (outside pockmarked).
• Larvae drop to ground and pupate until the next June – July.

Controls - Cultural or Non-chemical:
• Lay a barrier (landscape fabric, remay cloth) on top of soil under the tree—this prevents pupae from emerging from soil, as well as larvae entering soil in fall.
• Apple Maggot Traps—hang in trees in mid-late May.  Average emergence date in Alberta is June 15-23.

Controls - Chemical:
• None


 
 
 
 
 
 
Ash Bark Beetle

Plants Affected - Ash

Symptoms:
• Wilting, yellowish foliage.
• Check under bark for adults/galleries.

Controls - Cultural or Non-chemical:
• Keep garden debris free (ants are feeding on debris).
• Pour boiling water down hills.
• Keep area well watered-ants don't prefer wet areas.
• Control aphid colonies.

Controls - Chemical Controls:
• Pyrethrum
• Diatomaceous earth
• Doktor Doom Residual-yellow can


 

 

 

 

 

Ash Leaf Cone Caterpillar

Plants Affected - Ash

Symptoms - Leaves rolled into cones - damage cosmetic.

Controls - Cultural or Non-chemical Controls:
• Parasitic wasp is helping control.
• Handpick small infestations.
• Good leaf cleanup in fall.

Controls - Chemical:
• None – spraying will kill beneficial insects that provide control


 
 
 
 
 
 
Ash Plant Bug

Plants Affected - Green Ash

Symptoms:
• Leaves turn yellow, are mottled. May see stippling - (like a mite).
• Drought /stress related.
• Damage is cosmetic.

Controls - Cultural or Non-chemical:
• Keep trees stress free, especially in droughts.
• Prune any dead/dying branches.

Controls - Chemical:
• Apply Tanglefoot in spring to block adults travel.


 

 

 

 
Birch Leaf Miner

Plants Affected - Birch

Symptoms - Watch for mines in leaves, yellowing leaves.

Controls - Cultural or Non-chemical:
• Has been kept under control very well by beneficial insects.
• Keep trees well watered.

Controls - Chemical:
• Not necessary.


 
 
 
 
 
 
Boxelder Midge

Plants Affected - Boxelder

Symptoms:
• Leaves curl tightly, open to reveal white larvae

Life Cycle:
• Adults emerge in spring when first leaves are unfurling.
• Eggs are deposited into young folded leaves. Larvae appear a few days later and twisting/curling of foliage shortly after.
• In mid-late June larvae drop to the ground, work their way into soil and construct cocoons. In late summer they pupate, overwinter in the soil.

Controls - Cultural or Non-chemical:
• Prune off worst affected leaves (that can be reached), so less larvae drop to ground to pupate.  Problems are aesthetic, since less than 50% of the tree is usually affected.

Controls - Chemical:
• None


 
 
 
 
 
 
Cankerworm

Plants Affected - Fruit trees, maples, oaks and lindens

Symptoms - Defoliated leaves, sticky honeydew residue

Life Cycle:
• Spring Cankerworm - emerges as an adult in late March or early April, after overwintering as naked brown pupae about four inches under the group..  Eggs are laid, hatch and larvae start to feed.
• Fall Cankerworm - in fall male/female mate, female lays eggs, larvae hatch in spring.  Larvae feed then drop to ground and burrow. They emerge again in fall to mate and lay eggs.

Controls - Cultural or Non-chemical:
• Horticulatural Oil can be applied in late fall and early spring.
• To control both species, apply Tanglefoot around trunk on Labour Day weekend, then renew the sticky band in March, maintain until the May long weekend.
• Apply BTK from mid April until Late May (3-4 applications throughout).


 
 
 
 
 
 
Cottony Psyllid

Plants Affected - Ash, Elder   Plants stressed by drought are most susceptible.

Symptoms - Twisted, distorted foliage—eventually browns and drops.

Life Cycle:
• Overwinters as eggs laid along edges of bud scales.
• Eggs hatch in May/June.

Controls - Cultural:
• Insect is very difficult to control once feeding begins. After leaf drop in fall (while temps still above 0) spray branches with Horticultural Oil (use dormant application rate).
• Again in early spring once leaves are about 3” long (this is when eggs are mature) spray again with Horticultural Oil (use summer application rate).

Controls - Chemical:
• You may spot adults dropping from tree on silken threads in late spring; if you notice these spray insects with Ambush or Sevin insecticide.
• Neem Oil may provide some control; apply as a soil drench (neem oil is best mixed with warm water)


 
 
 
 
 
 
Dogwood Sawfly

Plants Affected - Dogwood

Symptoms:
• Foliage has holes in it.
• Larvae have white or cream coloring with black dots on body.
• Larvae turn darker with larger spots as they mature.

Controls - Cultural or Non-chemical:
• Handpick small amounts

Controls - Chemical Controls:
• Spray with Sevin, Malathion, or Ambush (BTK will not work because these are not larvae of moths and butterflies but larvae of sawflies).


Dusky Birch Sawfly

Plants affected - Birch

Symptoms - Clusters of yellow sawfly with black spots seen feeding around edges of leaves on birch.

Life Cycle - Pupae overwinter in soil and emerge in spring; larvae feed May to early July. A second generation may be seen in September

Cultural Control - Handpick larvae

Chemical Control - Malathion, Sevin, Ambush


 

 

 

 

 

 
Elm Leaf Miner

Plants Affected - Elm

Symptoms - Leaves are "mined"

Controls - Cultural or Non-chemical:
• With small infestations, handpicking mined leaves is effective.

Controls - Chemical Controls:
• Insecticidal soap or sevin applied in late May/June as soon as mines are first noticed.


 
Elm Scale

Plants Affected - Elm

Symptoms:
• Honey Dew, sooty mold.
• Branches die back.

Controls - Cultural or Non-chemical:
• With small infestations, run gloved hand along bark to dislodge scales.

Controls - Chemical:
• Horticultural Oil in early spring.


Erineum Gall Mite (Velvet Mite)

Plants Affected - Maple, Birch, Viburnum, Linden

Symptoms - Feeding by mites forms raised, velvety patches on leaves.

Controls - Cultural or Non-chemical:
• Remove affected leaves.

Controls - Chemical:
• Hortictultural Oil can be applied in spring before tree leafs out (smothers adults before leaves emerge and they start feeding).


Europhid Mite on Cranberry

Plants Affected - Cranberry

Symptoms - Small gall like growths are seen on the surface of maple leaves in early to mid summer.

Controls - Cultural or Non-chemical Controls:
• Prune out affected sections as soon as damage noted.
• Spray with Horticultural oil either infFall after leaves are shed or in spring before bud break.

Controls - Chemical:
• No chemical insecticides are effective; damage is cosmetic and will not harm tree.


 

 

 

 

 

Europhid Mite on Maple

Plants Affected - Maple

Symptoms - Portions of new leaves are covered in fuzzy like material; commonly mistaken for a fungal disease.

Controls - Cultural or Non-chemical Controls:
• Prune out affected sections as soon as damage noted.
• Spray with Horticultural oil either in fall after leaves are shed or in spring before bud break.

Controls - Chemical:
• No chemical insecticides are effective; damage is cosmetic and will not harm tree.


 
 
 
 
 
 
Hawthorn Lace Bug

Plants affected - Plants in the rose family (Hawthorn, Pear, Cotoneaster, Saskatoon).

Symptoms:

  • Adults are small bugs which appear to be covered in lace. Nymphs are dark brown to black and covered in varying amounts of spines
  • Stippled or mottled leaves with many lace bugs present
  • Feed in large numbers, leaves may be stained with their excrement

Life Cycle:

  • Overwinter as adults (Two generations per season)
  • Black eggs are laid in clusters on the underside of leaves in early spring
  • Nymphs emerge and feed on the underside of the leaves after about 3 weeks
  • 5 instars; 1st generation of adults emerge in mid-summer, 2nd in fall

Chemical Control - On smaller shrubs Doktor Doom House and Garden, no larger trees Ambush.


 
 
 
 
 
 
Leaf Cutter Bee

Plants Affected - Rose, Lilac, Ash, Virginia Creeper

Symptoms:
• Half moon shapes cut out of leaves.
• Use leaves to seal eggs into the cells of the hive.
• May pollinate garden crops - do pollinate alfalfa
• Cosmetic

Controls - Cultural or Non-chemical:
• Keep dead stems pruned back to live tissue.

Controls - Chemical:
• Not necessary.


 

 

 
 
 
Leaf Hopper - Not Whitefly

Plants Affected - many - seen lots on Ash, Linden, Virginia Creeper.

Symptoms:
• Sap suckers—deform leaves by stippling them.
• Insects jump away when you near the plant.

Controls - Cultural or Non-chemical:
• Strong jet of water will knock them off plants
• Ladybugs, birds feed on them.

Controls - Chemical:
• Insecticidal Soap
• Permethrin (note: Doktor Doom more effective)


 
 
 
 
 
 
Leaf Rollers on Aspen

Plants Affected - Aspen

Symptoms - Rolled leaves, defoliation.  Considered cosmetic.

Controls - Cultural or Non-chemical:
• Parasitic wasps help control.
• Tanglefoot at base of tree may prevent pupae from crawling up tree.

Controls - Chemical:
• Horticultural Oil in early spring may smother eggs.


 
 
 
 
 
 
Leaf Tiers of Aspen

Plants Affected - Aspen

Symptoms - Leaves are tightly rolled. Problem is considered cosmetic.

Life Cycle:

  • Overwinter as eggs, larvae hatch in spring, tie two leaves together and feed.
  • Larvae only feed for two weeks, but leaves remain curled.
  • Adults fly, mate and lay eggs on leaves in late summer/fall.

Cultural Control - Good leaf clean up in Fall

Chemical Control - Dormant oil in early spring. Neem Oil may assist in control.


 

 
Lilac Leaf Miner

Plants Affected - Lilac, Privet

Symptoms - Olive green patches that later turn into brown, blotchy areas.

Life Cycle:
• Mature larvae overwinter in soil, awake in spring and pierce leaf, laying eggs in late May in the evening, in rows on undersides of leaves. Hatch within 7-10 days.
• Larvae bore into leaf and feed between layers for about 3 weeks, then surface, roll up in leaves and feed again.
• 10 days later drop to ground, pupate and emerge again in early August for the second generation. These will feed until mid September then overwinter in soil.

Controls - Cultural or Non-chemical:
• Removal of affected leaves as they are noticed.

Controls - Chemical:
• None; larvae protected by leaf layers.


 
 
 
 
 
 
Maple Leafcutter Moth

Plants Affected - Maple, Birch, recently Saskatoon

Symptoms - Oval holes cut out of leaves, to be used by insect to "shield" itself

Life Cycle:
• Overwinters as pupa, emerges in spring to lay eggs as leaves unfurl
• Larvae feed as leafminers for a bit, then emerge from mine and create a shelter using disks they have cut from leaf.  As they mature they create bigger shelters using more disks from the leaf.  Drop to the ground in fall to overwinter.

Controls - Cultural or Non-chemical:
• Rake and destroy affected leaves.

Controls - Chemical:
• BTK - apply as larvae emerge from mines.


 
 
Micro Mites

Plants Affected - Various plants—see symptoms

Symptoms:

  • Alder and Maple - red bumps
  • Plum - ‘fingers’
  • Elder - looks like herbicide damage/cottony psyllid damage (can look like spaghetti).
  • Viburnum- looks like mildew initially. Red colouration follows.

Controls - Spray branches with Horticultural Oil in fall or early spring while trees are dormant.


 

 
Oak Gall

Plants Affected - Oak

Symptoms - Various growths caused by mites, wasps or aphids.

Controls - Cultural or Non-chemical:
• Good fall cleanup.

Controls - Chemical:
• Various galls at play – some overwinter on tree, some not. Spray Horticultural Oil in spring as a preventative.


 
 
 
 
 
 
Oak Gall Wasp

Plants Affected - Oak

Symptoms - Round to oval galls about 1/2” in diameter found on twigs/branches in clusters. New galls are green, old ones brown.

Life Cycle - Adult wasps lay eggs in leaf buds in fall. By early summer next season, larvae secrete chemical that causes plant tissue to enlarge (thereby creating gall). Gall envelops them. Late summer, adult emerges from the gall, mates and lays eggs again.

Cultural Control - Prune out galls.

Chemical Control - Spray trees with hort oil in late fall/early spring to destroy eggs.


 
Oak Mite

Plants Affected - Oak

Symptoms - Small round shaped multi coloured galls appear like 'Fruit Loops' on back side of Oak leaves.

Controls - Cultural or Non-chemical:
• Prune out affected portions when first noted.
• Damage is cosmetic as galls will not kill tree.

Controls - Chemical:
• No chemical controls of note.


 
 
 
 
 
 
OAK PHYLLOXERA APHID

Plants Affected - Oak—mostly English Oak, so not too common here.

Symptoms - Yellow spots (measles/chicken pox) turn into dead spots in June. Turn gall over, there will be a bright orange aphid.

Life Cycle - N/A

Cultural Control - Good Fall cleanup

Chemical Control - Neem Oil may assist in control.


 

 

 
 
 
Pear Slug

Plants Affected - Fruit trees, Cotoneaster, Mountain Ash, Hawthorn

Symptoms - Leaf skeletonizing in mid to late June and again late July/August

Controls - Cultural or Non-chemical:
• Pick off larvae, hose off with strong jet of water.
• Bark mulch may deter adults emergence.

Controls - Chemical:
• Not recommended-birds, parasitic wasps control these. If you choose to spray, use Safer's 3 in 1 Garden Spray.


 
 
 
 
 
 
Poplar Borer

Plants Affected - Trembling aspen, willow, balsam poplar.

Symptoms:

  • Varnish like resin and holes with boring dust on the stems. Larval galleries under bark.
  • Prefers main stems

Life Cycle:

  • Adults emerge late June. Females cut crescent shaped marks in bark in which to lay eggs.
  • Eggs hatch, larvae mine into bark and stay for summer and winter. Next spring enter the heartwood of tree and feed for 2 years; this is when you’ll notice sap.
  • Damage could be confused with Poplar and Willow Borer; see next page.

Cultural Control - Use heavy gauge wire; locate holes and stick wire in to pierce and kill larvae.

Chemical Control - None available


 Poplar Willow Borer

Plants Affected - Willow, balsam poplar, RARELY trembling aspen.

Symptoms:

  • Upper crown or whole branches broken over and dead, through which red-brown or white shavings exude. Piles of shavings on ground. Prefers smaller branches.
  • Irregular splits and holes in bark of tree.
  • You’ll see more sawdust than sap flower (Poplar borer more sap).

Life Cycle:

  • In summer, females chew holes in bark and lay eggs. Larvae burrow into upper bark first, then innerwood where they create meandering tunnels
  • Previously injured trees will have circular emergence holes that have scabbed over.

Chemical Control - None available.


 

 

 

 

 
Scurfy Scale

Plants Affected:
• Ash, Aspen, Cotoneaster, Dogwood, Willow
• Attacks mainly Cotoneaster, Rose Family.

Symptoms:
• Scales cluster together.
• Mistaken for fireblight, kills twigs/branches.

Controls - Cultural or Non-chemical:
• Prune damaged branches (disinfect between cuts).
• Natural predators include lacewings and ladybird beetles.
• Horticultural oil or Lime Sulphur can be applied in spring to suffocate eggs;apply half strength on Cotoneaster as they do not have a protective bud cover.

Controls - Chemical:
• Malathion, Permethrin end of June.


 Slugs

Plants Affected - Hosta, ligularia, and a wide variety of garden plants with low hanging vegetation

Symptoms:
• Ragged holes on plant, young slugs will shred the leaves.
• Slugs leave a slime trail as they travel, they are most active between 3am and 6am.

Controls - Cultural or Non-chemical:
• Crawling Insect Killer (Diatomaceous Earth) can be sprinkled around the plants.
• Safer’s Slug & Snail Killer
• Shallow traps with an attractant such as beer
• Handpick in the early morning.

Controls - Chemical:
• Corry’s Slug & Snail liquid or granular


Stink Bug

Plants Affected - Numerous.  Trees, Shrubs and Perennials

Description:

  • Various forms/colours will be seen - will generally have a large triangular plate on their back
  • Omit foul smelling substance when disturbed

Life Cycle: 

  • Adults overwinter in plant debris and in soil.  Emerge May - June, egg are laid in June/July, from egg to adult takes about 25 days

Controls

  • Though found in large numbers, rarely cause damage to the extent that warrants spraying insecticide
  • They are actually a predator of the Colorado Potato Beetles, each nymph can consume over 250 eggs.

 

 
 
 
Spidermites

 

Plants Affected - Numerous

Symptoms:
• Stippling—tiny dots in foliage.
• Yellowing of foliage—’haze’ on foliage

Controls - Cultural or Non-chemical:
• Strong jet of water
• Keep plants misted
• Fall debris cleanup

Controls - Chemical:
• Insecticidal Soap, miticide such as malathion, Safer's 3 in 1. Product must state:Miticide or that it treats Mites.


 
 
 
 
 
 
Tent Caterpillar

Plants affected - Aspen, Poplar mostly but also Apple, Ash, Elm.

Symptoms - Egg masses found in late spring; eggs covered with Form silken tents over themselves where they rest and feed.

Life Cycle - Eggs laid in early June, eggs hatch 4-6 weeks later and

Cultural/non-chemical Control:

  • Remove ‘tents’ - best done in late evening or early morning
  • Handpick, scrape cocoons off of branches in summer.
  • BTK - spray foliage with BTK, repeat within 5-7 days. Thorough coverage of the foliage is required.

Chemical Control - Not recommended, BTK very effective.


 

 
 
 
 
Thrip

Plants Affected - Numerous

Symptoms - White blotches or streaks on foliage/blooms

Controls - Cultural or Non-chemical:
• Good fall clean up of debris.

Controls - Chemical:
• Apply Doktor Doom to foliage early in season (mid-June). As this product persists on foliage for a few weeks, it should help to get one the generations.
• Doktor Doom House and Garden.


 
 
 
 
 
 
Viburnum Leaf Beetles

Plants Affected - Viburnum— high bush cranberry, European etc.

Symptoms:

  • Early damage appears as pin pricks—by June skeletonizing apparent.
  • In summer, lines of holes (egg chambers) can be seen along twigs of current season’s growth.

Life Cycle:

  • Eggs hatch in May, larvae begin feeding.
  • In June larvae drop to ground to pupate. Adult beetles emerge, females chew holes in twigs, lay eggs from summer to frost.

Cultural Control:

  • Early spring examine twigs for holes—prune out.

Chemical Control:

  • Dr. Doom House and Garden—as leaves expand in spring, look for larvae and spray these. Adults difficult to spray as they fly away when disturbed.

 

 
 
 
 
White Pine Weevil

Plants Affected - White Pine

Symptoms:
• Symptoms appear on most types of pine and sometimes spruce.
• Terminal leader of pine and spruce become curled over resembling a shepherds hook.
• Small exit and entry holes are seen at the base of the leader.

Controls - Cultural or Non-chemical:
• Remove leader.
• Trees must be kept healthy (well watered).

Controls - Chemical:
• No regulated chemicals.


 
Willow Leaf Blotch Miner

Plants Affected - Willow - mostly Laurel Leaf

Symptoms:
• Large brown blotches on leaves will start to ‘bubble’ revealing the larvae feeding between leaf layers.
• Leaves eventually yellow and drop.

Life Cycle - Adult moths overwinter, emerge in spring and lay eggs on undersides of leaves. Eggs hatch, larvae feed, spin silken covering on leaves or on ground. Adults emerge in August, overwinter.

Controls - Cultural or Non-chemical:
• Rake affected leaves well in fall, spray trees with horticultural oil in spring ONCE leaves emerge.

Controls - Chemical:
• None


 
Wooly Bears - Tussock Moth Larva

Plants Affected - Several

Symptoms - Damage is cosmetic.

Controls - No control required.