Yew Mealy Bug Diagnostic Guide

Dysmicoccus wistariae

Yew mealybug, Dysmicoccus wistariae, is a pest of ornamental yew. This pest can be difficult to see, as it resides on the interior of the plant. They are most commonly found on branch forks. Yew mealybugs can cause significant damage to affected plants and can be a nuisance as they secrete a sticky sap like substance called honeydew. Honeydew can coat surfaces such as sidewalks and attract a black sooty mold that looks unsightly. Commonly moved by shipment of plants from growers to nurseries, this insect occurs wherever yew grows.

Trees at Risk

Yew, rhododendron, maple, dogwood, and others.





Signs of Damage

  • Thinning, often yellow foliage on yew.
  • Waxy, white secretions and dead females on bottom and top of leaves.
Yew Mealy Bug

Physical Appearance

  • The yew mealybug is an oval, hemispherical insect with white coating and waxy filaments extending to the sides.  Its body segments are visible.
  • Insects are commonly found at branch forks.
Yew Mealy Bug


Yew Mealy Bug


  • One year life cycle.
  • Nymphs overwinter under bark scales or dead females.
  • Nymphs are active very early in the spring.
  • Females give birth to live young in mid-June.

Treatment Strategy

Monitoring the interior of the plant is important for identifying and diagnosing this pest. If sprays can be applied directly to the insects, they will be effective. If they cannot, systemic insecticides will work, though they will take more time to uptake. In severe infestations limbs can be removed to reduce the insect population.

  • Soil Application using Xytect 2F

    Dosage: 0.1 oz/ft of shrub height
    Timing: Preferable fall, but anytime during growing season
    Re-Treatment: Annual
    Xytect 2F Insecticide
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  • Foliar Spray using Distance

    Dosage: 0.5% - 1% RTSA Hort Oil™ + 8 – 12 fl oz Distance™/100 gal water
    Timing: 200-300 GDD
    Re-Treatment: Annual
    Distance Insect Growth Regulator
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Treatment Expectations

If timed correctly, sprays will work well. Systemic insecticides are very useful for controlling this insect.

A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy Use of the images does not imply endorsement of treatments by

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