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Standardized Sampling for Detection and Monitoring of Hemlock Woolly Adelgid in Eastern Hemlock Forests prepared by Dr. Scott Costa, University of Vermont. Presentation Goals. Introduce Hemlock woolly adelgid (HWA) Train HWA samplers. Hemlock Woolly Adelgid, Adelges tsugae.

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Standardized Sampling for Detection and Monitoring of Hemlock Woolly Adelgid in Eastern Hemlock Forests

prepared by Dr. Scott Costa, University of Vermont

presentation goals
Presentation Goals
  • Introduce Hemlock woolly adelgid (HWA)
  • Train HWA samplers
hemlock woolly adelgid adelges tsugae
Hemlock Woolly Adelgid, Adelges tsugae
  • Invasive Species
  • No Effective Natural Predators or Diseases
  • Explosive Population Outbreaks
  • Tree Death Shortly Follows
consequences of hemlock loss
Consequences of Hemlock Loss

Hemlock is Important

  • Protects Riparian Zones
    • Water quality
    • Water temperature
  • Provides Animal Habitat
  • Replaced By
    • Invasive plants
    • Less desirable trees
  • Poor Stand Recovery
    • Short-lived seeds

HWA Lifecycle – Explosive Population Growth

  • 2 generations/yr
  • 100+ eggs/adult
  • Crawlers crawl!
  • Nymph and adults immobile
  • Winged adult dead-end
very small in summer
Very Small in Summer

And very hard to see!

crawlers crawlers everywhere
Crawlers, Crawlers, Everywhere!
  • Abundant
  • Very Mobile
  • Nearly Invisible
how do hwa spread
How do HWA Spread?
  • Human Activity
    • Nursery crops
    • Hemlock logs
  • Natural
    • Wind dispersed
    • Animals: Birds, deer and small mammals
the sampling plan
The Sampling Plan
  • Monitor spread and level of infestation
  • Decision making for management action
  • Assess management success
  • Research tool
a good plan
A Good Plan
  • Simple to Use
  • Practical and Efficient
  • Has Defined Reliability
specific goals for sampling hwa within a stand
Specific Goals for Sampling HWA Within a Stand
  • Detection – Are they out there?
  • Characterization – What is the level of infestation?
sample lower branches
Sample Lower Branches
  • Inefficient to sample above ground level
  • Data indicates lower branches are suitable

Presence or Absence Sampling Plan

Presence or Absence

White Woolly Masses

Lower Branches

NOT Tree Condition

hemlock woolly adelgid sampling plan
Hemlock Woolly AdelgidSampling Plan
  • Examine 2 branches on up to 100 trees.
  • HWA can be detected with 75 % reliability when > 2 % infested trees.
  • Efficient determination of % trees infested using defined precision (0.25).
The Hemlock StandLimited stand information requiredStands 10 acres or more, but smaller OK tooStronger Hemlock component is better
where to sample on trees
Where to Sample on Trees
  • 2 Branches you can reach
  • Underside of last 1 meter
  • Ignore foliage quality
  • Base of needles – follow twigs
what to look for
What to Look For
  • Any evidence of woolly masses
    • Large egg sacks
    • Immature HWA
    • Scars of woolly masses
  • No counting
  • Not the typical HWA picture – initially have fewer HWA
if it doesn t look like hwa it probably isn t hwa
Spittle Bugs

Caterpillar Webbing

Scale Insects

Spider Webbing

Mite Webbing

Only at base of needles, usually

Only on underside, usually

If it doesn’t look like HWA it probably isn’t HWA

Bag Questionable Samples Especially in Low density Areas


Pine Aphid Wool

Drops of Pine Sap

Oak Skeletonizer

Spider Egg Sack

how to sample
How to Sample
  • Pick 4 general areas to sample (blocks)
  • Go into first block and pick a tree
  • Examine 2 branches (1 meter long end)
  • Limit your observation time (<1 min.)
  • Put results on survey sheet
  • Go to next tree and sample
    • Head in random cardinal direction
    • Go roughly 25 (2 step) paces
  • Go to next tree >>>>> Next Block


Once you find ONE HWA on a tree, you are done with that tree!

sampling path flexibility
Sampling Path Flexibility
  • Straight line vectors
  • Zigzag vectors
  • “W” paths
  • Any tree you can find paths
  • Object is to get a representative sample by moving through the stand
how many trees get sampled
How Many Trees Get Sampled
  • Detection – Sample until you find HWA or 100 trees, whichever comes first.
  • Characterization % trees infested – 8 to 100 trees depending on infestation.
  • Stop thresholds on data sheet.
when to sample
When to Sample?

Summer Sisten

Difficult to Detect

faq s
Stand is long and narrow

A lake in path!

25 (2 step) paces and no tree

Low foliage quality

The stand ended

No opposite branch

Blocks overlapped

Why avoid summer

Stopped sampling before threshold

What if HWA dead

What if I’m wrong

stay safe
Use a Compass

Bug Repellant

Water and Snack

Dress Properly

Be Smart

No heroes

Know your limits

Sample together

Stay Safe
forest training practice in hwa infested stand
Forest TrainingPractice in HWA Infested Stand
  • Raises Questions
  • Builds Confidence
  • Develops Proficiency
  • Fosters Consistency
hope for hemlock s future biological pest management
Hope for Hemlock’s future! Biological Pest Management
  • Insect-killing Fungi
    • Lecanicillium muscarium
  • Predators
    • Sasajiscymnus tsugae: Japan
    • Laricobius derodontid: British Columbia
    • Scymnus lady beetles: China
sampling plan development
Sampling Plan Development
  • Developed by Scott Costa, Department of Plant and Soil Science, University of Vermont
  • Research support from Joe Brown and the Harvard Forest Summer Ecology Internship
  • In collaboration with Bradley Onken, USDA Forest Service Northeastern Area State and Private Forestry
  • With support and funding from USDA-Forest Service Northeastern Area