Hemlock Woolly Adelgid

Adelges tsugae Annand

The Hemlock wooly adelgid (HWA), Adelges tsugae Annand, is a deadly introduced pest of forest and ornamental hemlock trees in the eastern United States. Its presence now encompasses most of the eastern states from Georgia to Maine and as far west as Kentucky.

Download Hemlock Woolly Adelgid Fact Sheet

Treatment Strategy

The treatment strategy for hemlock woolly adelgid is determined in part by the severity of the infestation.  Hemlocks that are showing dieback of more than 1/3rd of the tree are NOT good candidates for treatment and have too much infestation for treatments to be effective. However trees with less than 1/3rd dieback of their canopy can often be saved. The dead branches will not grow back and can either be pruned or will eventually fall out.

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Hemlock Woolly Adelgid Treatment Option 1

Newly infested or Preventative Treatment of Hemlocks

The goal of treatment for hemlock woolly adelgid is to stop feeding activity before the insect populations reach a point where significant damage is sustained. Applications of Xytect™ to the soil will provide up to two years of control of HWA. Treatment can be done at any time of the year as long as the soil is not frozen or saturated.

Application Type – Soil drench

DIY Product/Equipment Needed:

• Xytect™

• Soil drench kit

• Measuring or diameter tape

• Bucket or watering can

Hemlock Woolly Adelgid Treatment Option 2

Therapeutic Treatment of Hemlocks With Heavy Infestations

Hemlocks with a large population of adelgids are best treated with a combination of two products. Begin by applying a fast moving highly mobile insecticide to provide a quick kill of the insects called Transtect™. Follow up by applying a long lasting (up to 2 years) product that will protect the tree from reinfestation called Xytect™. Xytect™ moves rather slowly into the tree, often taking up to 90 days, so it is best supplemented with a fast acting product like Transtect™. Transtect is only needed one time as the initial treatment. Xytect™ should be applied every 2 years to prevent reinfestation.

Application Type - Soil drench

DIY Product/Equipment Needed:

• Xytect™

• Transtect™

• Soil drench kit

• Measuring or diameter tape

• Bucket or watering can

Hemlock Woolly Adelgid DIY Kit

Option 1

Application Type – Soil drench

DIY Product/Equipment Needed:

• Xytect™

• Soil drench kit

• Measuring or diameter tape

• Bucket or watering can

Option 2

Application Type – Soil drench

DIY Product/Equipment Needed:

• Xytect™

• Transtect™

• Soil drench kit

• Measuring or diameter tape

• Bucket or watering can

How Is It Spread?

All Hemlock wooly adelgids are female and the Hemlock woolly adelgid life cycle has six stages of development. There are two generations a year but, HWA enters a period of dormancy during the summer months. During cooler periods (October) HWA starts feeding again and continues throughout the winter months as it turns into an adult, laying up to 300 eggs from December to March. Reddish-brown crawlers hatch and attach their piercing sucking mouth parts to new growth at the base of the needles and begin feeding on stored starch in the tree. Eventually, the Hemlock wooly adelgid crawlers begin secreting white fluffy wool which can be seen on the underside of the outermost branch tips of hemlock trees.

Susceptible Trees

HWA develops and reproduces on all hemlock, but only causes damage to Eastern (Canadian) hemlock and Carolina hemlock.

Symptoms

• Woolly adelgid feed on the sap in the needles of hemlock trees, turning them grayish green.

• They can also feed on the sap of newly forming buds, killing them. This prevents the tree from developing new growth.

• The insect is so small that you’ll never see it, but what you will see is the white wooly substance covering the egg masses that give hemlock wooly adelgid its name.

• Infested trees will show dieback and eventually die.

Lookalikes

None

Related/Similar Problems

Hemlock elongate scale

Timing

Spring

Urgency

High

Risk of Spreading

Moderate

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