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Do Your Willow Trees Look Dead?

  • 23 Jul 2019
  • Written by  Big Lakes County

Do your willow trees look dead? Are the leaves changing color and falling off? It’s probably due to the Willow Leafminer.

The Willow Leafminer is a small gray moth native to North America. The caterpillars of this moth feed on willow leaves periodically causing extensive damage to willow stands in the province.

 

How do you recognize Willow Leafiner damage?

Take a look at the leaves. The damaged area of the leaf will be hollow with caterpillar droppings and sometimes with a

small (4-7 mm long), flat, pale yellowish caterpillar mining between upper and lower layers, if the damaged leaf is pulled apart. Mature caterpillars make cocoons to enter into a transition stage (pupa) in July during which the adult moths develop. The cocoon has a cellophane-like covering with a ring of denser silk around its margin. Cocoons are mostly located on the upper surface near the tip of the leaf.

 

How to control Willow Leafminer

• Usually, control measures are not necessary because leafminer outbreaks in most cases are controlled by natural enemies such as parasitoids, predators, and unfavorable weather conditions.

• Keeping willows healthy and vigorous help to mitigate leafminer impact. This can be done by avoiding soil compaction, stem and root injury, and water-logging.

 

• Applying fertilizer during spring and watering willows during droughts will also help to keep leafminer impact to a minimum.

 

• Use leafminer resistant willow varieties to avoid leafminer problem.

 

• If willows of high value are at stake you may consider the use of a systemic insecticide to reduce leafminer populations.

 

Download the Willow Leafminer brochure below.