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Dysmicoccus wistariae (Previously Pseudococcus cuspidatae)

Taxus mealybugs photographed on 6/9/2016 in Worcester County, MA. Photo: Tawny Simisky, UMass Extension.
Scientific Name: 
Dysmicoccus wistariae (Previously Pseudococcus cuspidatae)
Common Name: 
Taxus Mealybug
Growing Degree Days (GDD's): 
7-91 GDD's (Dormant); 246–618 GDD's, Base 50F, March 1st Start Date (Source: Robert Childs, UMass Extension and Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Cherry (Prunus spp.)
Dogwood (Cornus spp.) *Populations sometimes large on this host.
Japanese yew (Taxus cuspidata) (Weidhaas and Shaw, 1956) *Preferred host.
Japanese yew (Taxus cuspidata nana) (Hamilton, 1942) *Preferred host.
Maple (Acer spp.)
Rhododendron (Rhododendron spp.)
Wardi Yew (Taxus x media 'Wardii') (Hamilton, 1942) *Preferred host.
Yew (Taxus spp.) *Preferred host.
Insect Description: 

The taxus mealybug is thought to occur throughout the Northeastern US, including Massachusetts, New York, Connecticut, New Jersey, Pennsylvania, and Ohio. Its distribution also reaches into the central United States (Johnson and Lyon, 1991). Weiss (1915) first reported this species from Rutherford, New Jersey on Taxus cuspidata brevifolia and Rau (1937) described it as a new species, and a likely introduction from Japan in 1915 on T. cuspidata. Adult females are 0.16 inches long covered with a white powdery wax. Females may appear like they have 4 longitudinal lines in this wax, beneath which the body appears red in color. 15 filaments (waxy protrusions) are found along each side of the body with a longest pair at the rear end which is approximately 1/3 length of the body (Hamilton, 1942). First instar nymphs are reported as the overwintering life stage in New Jersey. They may be found in bark crevices on the host plant. In April and May few live mealybugs are found. However, by mid-June the population may increase considerably (Hamilton, 1942). Adult female taxus mealybugs are present from June to August and give birth to live young in the early summer. Nymphs and adults have been reported in Massachusetts in June but no eggs or young nymphs were seen (Weidhaas and Shaw, 1956). The exact life cycle and timing for this species is not fully understood. Weidhaas and Shaw (1956) call for further study of the life cycle of this insect, but Hamilton (1942) reports that live young are produced by this species (no eggs are laid). A single generation may occur per year in Connecticut and points northward; however, in New Jersey and points south, two or three generations per year may occur (Johnson and Lyon, 1991). There is discrepency on this, however, as Weidhaas and Shaw (1956) report two generations per year possible in Massachusetts. Adults are reported to disappear on plants by September (Hamilton, 1942). Yew (Taxus spp.) are the primary host plants. Others in the above list are rarely impacted by this insect with the exception of possibly dogwood (Cornus spp.) where large populations have sometimes been reported (Johnson and Lyon, 1991). The taxus mealybug may be confused with the Comstock mealybug (Pseudococcus comstocki; also introduced into eastern North America from Asia) which may sometimes be found on Taxus spp. The two may be differentiated by the following: the taxus mealybug has a red body and red fluid when the body is squished; the Comstock mealybug has a brown body and brown fluid when squished. The Comstock mealybug also produces an ovisac, and the taxus mealybug does not (Hamilton, 1942).

Damage to Host: 

The taxus mealybug feeds on the inner bark tissue of the trunk and branches of its host plants. This feeding can lead to sparse looking plants that have lost foliage, with any remaining needles caked in honeydew (liquid sugary excrement). That honeydew becomes the location for sooty mold to build up, which does not feed on the plant itself (but rather the sugary insect waste product) but makes the coated plant parts appear black in color. Moderate infestations can be detected by looking for these insects in the crotches of twigs and branches, often in clusters. Severe infestations of taxus mealybug on their host plants may cause stunting of plant growth. By midsummer, the insects may become very abundant.


Visual monitoring of the taxus mealybug may require moving apart tight branches and foliage of host plants (particularly Taxus spp.) in order to see the insects within. Look for evidence of taxus mealybug presence, including but not limited to the insect life stages themselves, but also honeydew and black sooty mold. The insects sometimes cluster on the undersides of branches, allowing them to be easily missed by the observer (Weidhaas and Shaw, 1956).

Cultural Management: 

Proper planting and maintenance can help reduce additional stressors on infested host plants. If only a single branch or few branches are infested with taxus mealybugs, they may be pruned out and destroyed. 

Natural Enemies & Biological Control: 

Hamilton (1942) writes: "During April of 1941 the writer found the bodies of many females which had been killed by parasites. In June many of the full grown or nearly full grown females showed parasitism and later a number of small Hymenoptera parasites emerged. These have not been identified."

Chemical Management: 

Acephate (NL)

Acetamiprid (L)

Azadirachtin (NL)

Beauveria bassiana (NL)

Bifenthrin (NL)

Bifenthrin+imidacloprid (L)

Buprofezin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Chromobacterium subtsugae (NL)

Clothianidin (NL)

Cyfluthrin (NL)

Dinotefuran (NL)

Fenpropathrin (NL)

Flonicamid+cyclaniliprole (N)

Tau-fluvalinate (NL)

Gamma-cyhalothrin (L)

Horticultural oil (L)

Imidacloprid (L)

Insecticidal soap (NL)

Isaria (paecilomyces) fumosoroseus (NL)

Lambda-cyhalothrin (L)

Malathion (L)

Neem oil (NL)

Permethrin (L)

Pyrethrin+sulfur (NL)

Pyriproxifen (eggs, nymphs) (L)

Spinetoram+sulfoxaflor (N) 


Taxus plants have thick foliage that may protect mealybugs from chemical management applications, particularly contact insecticides (Weidhaas and Shaw, 1956). Thorough coverage of the insects is necessary if choosing a chemical management option.

Active ingredients that may be applied systemically include: acephate (injection), acetamiprid (injection), azadirachtin (injection), clothianidin (soil drench), dinotefuran (soil drench), imidacloprid (soil drench), and neem oil (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .