Working Backwards: Problem with Plant Identify the Plant No Understanding Clues from Plant Damage Are insects involved? Disease, to Identify Insect Pests Fertility, or other Issue PJ Liesch Yes
UW Insect Diagnostic Lab Do you recognize the Yes No [email protected] insect(s) involved? Twitter: @WiBugGuy Collect Samples and Clues
insectlab.russell.wisc.edu Do you have the Diagnosis Yes resources to ID?
Contact Diagnostic Lab No University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Garden Insects of North America What if the Insect is Gone?
▪ 500+ pages & tons of color photos ▪ Image RICH ▪ Covers garden & landscape pests ▪ Low cost (~$30) ▪ Focuses on signs of insects
▪ Chapters are based upon type of plant damage: ▪ Variety of images ▪ Leaf chewers Helps with the unusual cases ▪ Sap Suckers ▪ ▪ Gall Makers Cost ($) ▪ Twig/Stem Damagers ▪ ▪ Trunk & Branch Borers
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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IPM of Midwest Landscape Plants Anatomy Dictates Damage Insect anatomy dictates the type of damage caused to plants ▪ Chapter 4: Symptom Categories of Plant Damage ▪
▪ Mouthparts usually the structures involved ▪ Sometimes other parts as well (e.g. ovipositor)
▪ Anatomy varies by type of insect (beetles, true bugs, etc.)
▪ Anatomy sometimes varies by stage of development ▪ Ex. caterpillars vs moths/butterflies http://cues.cfans.umn.edu/old/ipmbook.htm
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Insect Mouthparts Insect Mouthparts: Types
Chewing Insect mouths contain 4 basic Rasping- parts: Scraping • Labrum • Mandibles • Maxillae • Labium
These 4 basic parts have been modified through evolution for Piercing-Sucking different functions
University of Wisconsin: University of Wisconsin: Sponging Insect Diagnostic Lab Insect Diagnostic Lab
7 8 Chewing Mouthparts Piercing/Sucking Mouthparts Used to physically chew/cut off pieces of plant material ▪ ▪ Used to drink liquids Signs: holes, notches, leaves gone entirely, etc. ▪ ▪ Can’t chew holes if they wanted to! ▪ Also used by borers and leafminers ▪ Signs: discoloration, speckling, curling/distortion Key groups with chewing mouthparts: ▪ Key groups with chewing mouthparts: ▪ Beetles ▪ True bugs: aphids, leafhoppers, plant bugs, scales, etc. ▪ Caterpillars ▪ Sawflies Adult moths/butterflies ▪ ▪ Ants/bees/wasps Some bees/wasps ▪ ▪ Grasshoppers ▪ Mosquitoes Walking Sticks ▪ ▪ Mites such as spider mites ▪ ▪ Earwigs ▪ Etc. University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Rasping Sucking Mouthparts Working Backwards:
▪ Asymmetrical mouthparts ▪ Sometimes, damaging insects may be gone or hard to find, so looking at the signs/symptoms and working ▪ Initially scrape plant materials, then slurp up liquids backwards is a critical skill ▪ Signs: pale streaks/spots
In other cases, there may be multiple types of insects ▪ Key groups with chewing mouthparts: ▪ present and we need to figure out which one is the Thrips ▪ culprit
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Host Plant Specificity Main Insect Symptoms on Plants
▪ While some insects are broad generalists (ex. 1. Chewing on foliage, petioles, or twigs Japanese beetle), there are many insects specialize on certain types of plants 2. Discoloration 3. Distortion of plant tissues ▪ Knowing the host plant can be an invaluable clue 4. Dieback or dropping of plant parts
To be a good entomologist, be a good botanist first! 5. Other signs: droppings, cast skins, etc.
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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1) Chewing on Leaves, Needles, Petioles Defoliation
▪ Large portions of leaves or entire leaves eaten away ▪ Defoliation Top Suspects: ▪ Shot Holes ▪ ▪ Caterpillars: gypsy moth, eastern tent caterpillar, forest tent ▪ Notched Margins caterpillar, euonymus caterpillar, fall webworm, and many ▪ Skeletonization others! ▪ Sawflies: elm sawfly, European pine sawfly, dogwood sawfly, dusky birch sawfly, etc. ▪ Others: beetles (such as May/June beetles), grasshoppers, walkingsticks, earwigs, slugs
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
15 16 Eastern Tent Defoliating Caterpillars Defoliating Caterpillars Caterpillar Gypsy Moth ▪ Many other caterpillar species can be found in the landscape Caterpillar ▪ To narrow down: appearance, host plants, time of year Redhumped Oakworm Linden Looper
Oak/beech in late summer Linden and other hardwoods in spring
Whitemarked Tussock Moth Cankerworms (several species)
Forest Tent Caterpillar ManyUniversity hardwood of trees Wisconsin–Madison in summer University of Wisconsin: Fall Webworm Insect Diagnostic Lab Insect Diagnostic Lab summer Many hardwood trees
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Defoliating Sawflies Defoliating Sawflies Elm Sawfly (Typical) Dogwood Sawfly
Dusky Birch Sawfly
Mountain Ash Sawfly
Elm Sawfly (Orange Form)
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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European Pine Sawfly Other Conifer Sawflies ▪ Many other sawfly species are associated with conifers “Charlie Brown” Damage ▪ To narrow down: appearance, host plants, time of year
White Pine Sawfly Yellowheaded Spruce Sawfly
White/red pines in summer Spruces in late spring & early summer
Redheaded Pine Sawfly Balsam Fir Sawfly
Group of European University of Wisconsin–Madison University of Wisconsin: Pine Sawfly Larvae Insect Diagnostic Lab Insect Diagnostic Lab Mugo/Jack pines; 2 gens per summer Balsam fir and spruces in summer
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Other Defoliatiors: Shot Holes May/June Beetle ▪ Small holes within foliage
Top suspects: Northern ▪ Walking Stick ▪ Small caterpillars ▪ Leaf beetles General defoliators Post Oak ▪ Grasshopper Slugs ▪ Shot hole diseases
University of Wisconsin–Madison Insect Diagnostic Lab University of Wisconsin: Insect Diagnostic Lab
23 24 Viburnum Leaf Shot Holes: Beetle Special Case: Hail Damage
▪ Hail can also cause shot hole injury or tearing of foliage ▪ Also check for damage / bruising on upper side of twigs/branches
Shot Hole Diseases
Lily Leaf University of Wisconsin: Beetle University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Notched Margins Examples Notched Margins Black Vine Weevil ▪ Small notches chewed out of edges of leaves
▪ Top suspects: weevils, small caterpillars, small sawflies
Strawberry Root Weevil Two Banded Japanese Weevil
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Notched Margins Examples Special Case: Notched Margins
Leafcutter Bees
Caterpillars Small (Small) Sawflies Many species exist; many different Many species exist; many different hardwood plants attacked Can cause minor notching. hardwood plants attacked They are beneficial pollinators!
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Rose Examples of Skeletonization Chafers Skeletonization ▪ Leaves have a lace-like appearance; damage may go Oak Leaf partially or entirely through the leaf tissues Skeletonizer
Top suspects: some beetles, sawflies, and small ▪ Imported Willow Leaf Beetle caterpillars Japanese Beetle & Skeletonization Injury
Elm Leaf Beetle
University of Wisconsin: University of Wisconsin: Maple Trumpet InsectMany Diagnostic hardwood Lab plants in summer Insect Diagnostic Lab Skeletonizer
31 32 Scarlet Oak Examples of Sawfly 2) Discoloration Skeletonization
Roseslug Sawfly ▪ Stippling/Speckling ▪ Leafmining On oaks in summer ▪ Yellowing/Discoloration
Pearslug Sawfly
On roses in spring & early summer ▪ Plant diseases can sometimes cause similar symptoms!
University of Wisconsin: On rosaceous plants University of Wisconsin: Insect Diagnostic Lab in late summer Insect Diagnostic Lab
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Rose Leafhopper Stippling / Speckling Stippling:
▪ Foliage has a speckled appearance Lace Bugs ▪ Can sometimes resemble sand paper
▪ Caused by insects/mites with sucking mouthparts
Top suspects: ▪ Lacebugs ▪ Ash Plant Bug ▪ Plant Bugs ▪ Leafhoppers ▪ Thrips ▪ Spider mites
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Two-Spotted Spider Mites Up-close View of Thrips Stippling: Thrips Damage to Foliage Spider Mite Stippling Injury
Thrive under hot/dry conditions
Produce webbing when populations high
Spruce Spider Adult Thrips Mite Injury (Conifers)
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab Thrips Damage to Flower
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Leafminers Leafmining Elm Leafminer (Sawfly) ▪ Brownish patches within foliage ▪ May be linear, circular blotches, meandering Hawthorn Leafminer (Sawfly) ▪ Responsible insects are tiny; use chewing mouthparts to tunnel within the foliage
Tend to be very host plant specific ▪ Birch Leafminer (Sawfly) ▪ Top suspects: ▪ Caterpillars ▪ Flies Locust Sawflies Leafminer ▪ (Beetle) ▪ Beetles University of Wisconsin: Leafminer on University of Wisconsin: Insect Diagnostic Lab Poplar Insect Diagnostic Lab
39 40 Boxwood Leafminer (Gall Midge) Needleminers ▪ Tiny (~1/8” long) yellow larvae live and feed within leaves of boxwood ▪ Adults active and laying eggs in June
Spruce Leafminer (Caterpillar) Dissected leaf w/ larvae and pupae
Boxwood Shrub Arborvitae Leafminer (Caterpillar)
University of Wisconsin–Madison Insect Diagnostic Lab University of Wisconsin: Leafmines Emerging Adults Insect Diagnostic Lab
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Yellowing/Discoloration: Yellowing / Discoloration ▪ General discoloration of plant tissues
▪ Can be a vague symptom; can resemble diseases, fertility issue, etc. Potato Leafhopper & Plant Injury Top suspects: ▪ ▪ Aphids ▪ Plant bugs ▪ Mealybugs ▪ Whiteflies ▪ Leafhoppers Certain Mites ▪ Yellowing on Aphids University of Wisconsin: Grapes due to University of Wisconsin: Insect Diagnostic Lab leafhopper feeding Insect Diagnostic Lab
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Special Case: Four-Lined Plant Bug Erineum Galls
Up-Close View of Erineum Gall
Four-Lined Plant Bug (Nymph) Gall patches on Maple Four-Lined Plant UniversityBug (Adult)of Wisconsin: University of Wisconsin: Eriophyid Mite Insect Diagnostic Lab Insect Diagnostic Lab
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3) Distortion Curling / Cupping Foliage distorted and curled ▪ Curling/Cupping ▪ ▪ Caused by insects with sucking mouthparts ▪ Galls of leaves, twigs, flowers ▪ Diseases & herbicide injury can cause similar symptoms
Top suspects: ▪ Aphids ▪ Plant diseases can ▪ sometimes cause similar ▪ Plant Bugs symptoms! ▪ Leafhoppers Psyllids ▪
University of Wisconsin: University of Wisconsin: Curled Viburnum Insect Diagnostic Lab Insect Diagnostic Lab Leaves due to Aphids
47 48 Snowball Aphids (Viburnum) Curling/Cupping Curling/Cupping
Leafhopper Injury Honey locust Plant (Apple) Bug (Honey locust)
Boxwood Psyllid (Boxwood)
University of Wisconsin:Spiny Witchhazel University of Wisconsin: Insect Diagnostic LabGall Aphid (Birch) Insect Diagnostic Lab Nymph Adult
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Galls Wasp Galls
▪ Sever distortions of plant tissues in response to insects, Noxious Oak Gall mites, or certain diseases (Swamp White Oak) ▪ Can be caused by a wide range of insects/mites Mostly a cosmetic issue; treatment usually not feasible ▪ Tend to be very host-plant specific! ▪
Spiny Witch Hazel Gall Adult Gall Wasp Top suspects: Aphid (Witch Hazel) ▪ Oak Apple Gall ▪ Wasps (tiny!) (Many oaks) ▪ Aphids & relatives ▪ Gall midges ▪ Mites ▪ Others: Beetles, flies, etc. University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Hedgehog Gall Elm Cockscomb Aphid (White Oak) Wasp Galls Aphids & Relatives
Spiny Rose Gall (Rose)
(Slipper Elm) Pouch Gall Aphid Jumping Oak Gall (Bur & Swamp White Oak)
Hickory Leaf Stem Gall Aphid (=Phylloxera)
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Cooley Spruce Gall Adelgid Larva Adult Fly Aphids & Relatives Midge Galls
Balsam Gall Midge
Eastern Spruce Gall Adelgid
Maple Gall Midge
University of Wisconsin: Inside of Adelgid Gall University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
55 56 Eriophid Mite Eriophyid Mite Galls Eriophyid Mite Galls Ash Flower Gall Mite (Ash) Maple Bladder Gall (Maple) Erineum Gall (Maple) Credit: Eric Erbe, USDA, Bugwood.org
Maple Spindle Gall Spindle Gall University of Wisconsin: (Maple) University of Wisconsin:(Cherry) Insect Diagnostic Lab Insect Diagnostic Lab
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4) Dieback or Dropping Psyllids ▪ Shoot dieback ▪ Branch/Trunk Dieback ▪ Dropped plant parts
Hackberry Psyllids
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Shoot Dieback Special Case: Damage Due to Oviposition Occasional egg Laing (oviposition) injury can occur from ▪ ▪ Tip of shoot dying insects such as treehoppers and tree crickets May involve insect tunneling ▪ ▪ Oviposition scars can kill/stunt shoots, twigs & small branches Check for exit holes, frass, etc. ▪ Buffalo Treehopper (Polyphagous) Oviposition Scars ▪ Top suspects: ▪ Caterpillars ▪ Beetles
European Pine Shoot Moth (Pine) University of Wisconsin–Madison Tree Cricket w/ University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab White Pine Weevil Oviposition Scars
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Dieback of Branches or Trunk Borers
▪ Often indicates serious issues ▪ Can either be primary or secondary borers ▪ Check for signs of disease, technical injury, etc. ▪ Important clues: host plant, size of holes, presence of frass, part of plant (twigs, branches, trunk, etc.) ▪ Top suspects: Borers ▪ Bronze ▪ Scale insects Birch Borer
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Exit Holes from Borers Insect Diagnostic Lab
63 64 Special Case: Sapsucker Injury Dropped Plant Parts Can resemble borer activity Maple Petiole Borer ▪ ▪ Dropped plant parts ▪ Holes regular in size, often in linear or grid-like pattern ▪ Typically tolerated by trees; occasionally problematic ▪ Top suspects: ▪ Boring insects ▪ Squirrels Yellow-Bellied Sapsucker and Damage Oak Twig Pruner
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab Twig Girdler
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Special Case: Squirrels 5) Other Signs
Extensive Trig Drop
▪ Honeydew / sooty mold ▪ Frass / fecal spots ▪ Silk ▪ Protective cases / shelters Diagonal Cuts ▪ Waxy coverings ▪ Exuviae (shed exoskeletons)
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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Other Signs: Other Signs:
Frass from Clearwing Borer on Ground Near Trunk
Up-close view of Magnolia Scale Zimmerman Pine Moth: Oozing Pitch
Magnolia Scale, Honeydew, Sooty Mold University of Wisconsin: and Scavenging Insects UniversityClearwing of Wisconsin: Pupal Insect Diagnostic Lab Insect CaseDiagnostic and LabExit Hole
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Other Signs: Silk Questions?
PJ Liesch UW Insect Diagnostic Lab Eastern Tent Caterpillar [email protected] Twitter: @WiBugGuy
Euonymus Caterpillar Fall Webworm insectlab.russell.wisc.edu
University of Wisconsin: University of Wisconsin: Insect Diagnostic Lab Insect Diagnostic Lab
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