Janet Knodel

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Common Insects Problems in Trees Shrubs in
North Dakota
Janet Knodel Extension Entomologist
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Master Gardener Basics

• Proper insect identification
• Understand pest biology
• Life cycle (complete or incomplete metamorphosis)
• Hosts
• Recognize feeding injury
• Types piercing-sucking and chewing
• Severity of injury negatively impact health of
  tree?
• Control necessary?
• Know when and how to apply control methods
• USE Integrated Pest Management IPM approach
• Insecticides as last resort

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Proper Identification of Insects
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Complete Metamorphosis

• Egg to larval stages to pupae to adult
• Larvae look different from adult
• Pupal stage (inactive)

beetles moths/butterflies bees/wasps flies
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Incomplete Metamorphosis

• Egg to larval stages (nymphs) to adult
• Larvae look similar to adult
• No pupal stage

grasshopper aphid plant bug
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Mouthparts Chewing

• Holes in plant leaves or other parts
• Skeletonized leaves
• Tunneling in wood

mandibles
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Mouthparts Piercing-Sucking

• Wilting plants
• Dead spots in tissues
• Honeydew

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I P M
Integrated Pest Management for
Insects
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information based
The IPM Continuum
biocontrol
System Based
biorational
predictive model
pest monitoring
Conventional
resistant varieties
cultural controls
chemical based
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Mouthparts Piercing-Sucking

• Wilting plants
• Dead spots in tissues
• Honeydew

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Aphids

• Found on most plants
• Various colors (black, green, )
• Two tailpipes or cornicles
• Winged or wingless
• Reproduce rapidly (asexual)
• Produce large amounts of honeydew
• Ants move and protect them
• Black Sooty mold

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Plant Bugs or Leafhoppers Ash plant bug

• Adult ½ inch, tan colored with pinkish markings
  on back
• Nymph
• 2 generations per year
• Midsummer
• Late summer
• Overwinter as eggs in bark

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Ash plant bug

• Pierce host tissue and suck plant sap causing
  yellow spotting of leaves
• Leaf mottling
• Deformed leaves
• Premature leaf drop
• HEALTHY trees tolerate injury
• Foliage damage is observed throughout tree
  canopy, use insecticide for control

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Cottony Ash PsyllidNew Insect Pest in North
Dakota

• North Dakota Dept of Ag first observations in
  2005
• Fargo
• Grand Forks
• Dickinson
• Minot
• Hankinson

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Cottony Ash Psyllid - Hosts

• Black ash, Fraxinus nigra
• Mancurian ash, Fraxinus mandshurica
• Hybrids of these two species
• Northern Treasure
• Northern Gem
• Not know to feed on green ash or white ash

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Cottony Ash Psyllid
Adult
Adult light green, small size 3mm Nymph
light green to yellow-green
Nymph
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Scale Insects

• Cottony maple scale insect
• Cottony egg sacs with 1,500 eggs
• Egg hatch in late June or July

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Cottony maple scale

• Crawlers
• Tiny, brown
• Feed on underside of leaves
• Move back to branch in fall
• Maple, popular, basswood, elm

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Cottony Cushion
Lecanium Scale

• The first instar nymphs have legs and antennae
  and are called a crawler.
• After the first molt the insect becomes sessile
  and attaches itself to the plant.
• The insect then covers itself with a waxy,
  cottony, or scale like covering.

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Pine Needle Scale

• Overwinter as eggs
• hatch in May
• in August, needles spotted with white scales

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Oystershell Scale
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Spider mites

• Very small
• Injury symptoms
• Yellowing
• Spots with no green tissue
• Webbing
• White paper for sampling
• Hot dry conditions
• Increase mite populations

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Predatory Spider mites

• Dont confuse this beneficial mite with bad
  phytophagous mites
• Active, fast moving
• Longer legs
• Feeds on phytophagous mites

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Mouthparts Chewing

• Holes in plant leaves or other parts
• Skeletonized leaves
• Tunneling in wood

mandibles
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Leaf Feeding Caterpillars Tent Caterpillars

• Prairie - large silk tents around fork or branch
• Forest - no tents
• one generation
• eggs laid in fall
• larvae hatch in
• spring
• larvae leave web
• (when present) to feed

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Tent caterpillar

• Webs constructed in V of limbs
• Caterpillars leave web to feed

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Tent caterpillar

• Defoliation
• Hardwoods chokecherry, ash, aspen, elm, maple,
  oak, poplar
• Larvae feed outside web making control with
  insecticide easy
• Bt insecticides work well with young larvae
• Pyrethrin or synthetic insecticides  

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Fall and Spring Cankerworms
Cankerworm caterpillar
Male and wingless female moths caught in
tanglefoot
Cankerworm feeding injury
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Fall and Spring Cankerworms
Cankerworm caterpillar
Wingless female moth
Cankerworm feeding injury
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Fall Webworm
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Fall Webworm

• Caterpillars stay in protection of web
• expand web for more food as leaves are eaten
• Difficult to control when webs fully
  developed

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Other Leaf Feeding InsectsPear slug sawfly

• Adult 3/16th of inch, shiny dark wings
• Larvae slug-like, covered with slime
• Life Cycle
• Overwinter as larvae
• Pupate in spring
• Emerge as adults
• 2 generation a year
• Hosts cotoneaster, fruit trees, hawthorn,
  mountain-ash

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Pear slug sawfly

• Defoliation
• Leaf skeletonization
• Premature leaf drop
• Little damage to host
• Control
• Wash off larvae with strong jet of water
• Sprinkling wood ash on larvae
• Insecticidal soap or conventional insecticides

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Birch leafminer

• Adult sawfly, ¼ inch long, black, fly-like wasp,
  do not sting
• Larvae very flat, white with 3 black spots,
  live within birch leaves
• Damage
• Large blotch mines in leaves
• Multiple generations and high populations forces
  tree to refoliate and reduces ability to produce
  food
• Makes tree more susceptible to bronzed birch
  borer

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Birch leafminer Life cycle

• Overwinter as mature larvae
• Spring pupate and transform into adults
• Adults emerge as newly expanding foliage of
  birches
• Mate and oviposit on upper leaves in sunny
  locations
• Egg hatch in 7 to 10 days
• Larvae mine leaf for 14 to 20 days
• 2 to 3 generations a year

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Birch leafminer

• Control
• Cultural control
• Pupation barrier
• Resistant birches
• River birches (B. nigra)
• Dahurian birches (B. davurica)
• Chemical control
• Target adults
• Systemic insecticides for larval control
• Orthene, imidacloprid
• Timed sprays using Degree-day
• 190-290 DD (50 degree F base) first generation
  of larvae susceptible to control

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Yellow-headed Spruce Sawfly

• Adults emerge in spring
• young larvae feed on new needles
• rear up in S shape
• larvae drop to ground in July

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Wood Boring InsectsBark beetles (Scolytinae)

• Symptoms bark of dead or dying limbs, small
  holes, galleries underneath bark
• Keep trees in good health
• Usually attack stressed or dying trees in spring

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Bronzed birch borerBuprestidae

• Adult bullet-shaped, with metallic bronzed reflection
• Larvae flat-headed borer, legless, 1.25 inch
  when full grown
• Life cycle 1 to 2 years
• Adults emerge late June through August
• Injury larval tunneling beneath bark

D-shaped exit holes
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Bronzed birch borer

• Young, transplanted or weakened or dying trees
  most susceptible
• Symptom bumpy branches
• Control
• Adult to prevent egg laying
• Foliar insecticide in mid-June and twice more at
  3-week intervals until August
• Imidacloprid soil drenches
• Insecticide injections by professional variable
  results
• Destroy heavily infested limps
• Resistance Brown-barked river birch

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Lilac or Ash Borer Sessidae
Wasp-like moths emerge in June
Die-back and breakage
larvae mine sapwood
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Emerald Ash Borer EXOTIC!Cerambycidae

• Native to East Asia
• Likely introduced via solid wood packing material
• First detected in Detroit, MI area in 2002
• Probably established 7 to 12 years previously

Agrilus planipennis
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Emerald Ash Borer - Hosts

• Green ash
• Black ash
• White ash
• Blue ash
• Including all cultivars

-Color varies from bronzed to golden green -
Darker metallic purplish green wing covers
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Emerald Ash Borer

• Has killed an estimated 10 million ash trees in
  SE Michigan

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Emerald Ash Borer - Symptoms

• Thinning canopy starting in upper 1/3 of tree
• Epicormic shoots or suckers

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Emerald Ash Borer - Symptoms

• D-shaped exit holes
• S-shaped tunnels from larval feeding

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Emerald Ash Borer - Symptoms

• Vertical splits in bark
• Activity by woodpeckers

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mossy rose gall wasp
Gall Insects

• aphids
• psyllids
• midges (flies)
• wasps
• Mites

Hackberry nipple gall (psyllid)
- Usually not harmful to plants - Gall forms from
salivary secretions from pest
petiole leaf gall aphid
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Maple bladder gall mite
Ash flower gall mite
oak flake gall
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The remaining slides are examples of Good or
Beneficial Insects
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Preying mantis
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Preying mantis egg case
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Lady beetles . . . Aphid predators
larva
pupa
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Ground beetle
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Orius, a.k.a. Pirate bug
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Pirate bug feeding on aphid
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Nabis, a.k.a. Damsel bug
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Damsel bug nymph
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Big-eyed bug
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Spiny soldier bug
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Spiny soldier bug nymph
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Assasin bug
wheel like hump
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Lacewing adult
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Lacewing eggs
stalk
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Lacewing larva
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Syrphid fly
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Syrphid fly larva
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Wasp or Hornet
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Parasitic wasp
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Aphid parasite
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Aphid mummy parasitized by wasp
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Parasitic wasp egg-parasite
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Parasitic wasp egg-parasite
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Parasitic wasp larvae emerging from host
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Spiders
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Predatory spider mite
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Bacteria-killed caterpillar
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Virus-killed caterpillar
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