I have large areas of white stuff on my yew bush which is about 9 years old. I also saw white bugs about 1mm in size, moving.
The needles are dying. Please identify and suggest remedies.
It is positioned in full sun, between pathways.
Thank you for contacting the Toronto Master Gardeners. From your description, it sounds like your yew (Taxus spp.) has become infested with mealybugs. In heavily infested plants, growth will be irregular or cease, and leaves will turn yellow and drop. Untreated plants can die.
This is some information from our response to a previous question about mealybugs :
‘These small sucking insects cover their bodies with a white, cottony substance which is what makes them easy to identify. Mealybugs are a type of scale insect that feed on the sap of both indoor and outdoor plants. Female mealybugs often gather in dense numbers. Mealybugs get their name from the powdery waxy layer that they produce for protection as they feed. These pests can damage trees & shrubs by sucking out their sap. They also excrete a honeydew which when produced in great amount encourages the growth of sooty mold, and attracts other insect pests. The insects overwinter on plants as eggs within white cottony masses. The eggs hatch in the spring, and the nymphs feed on leaves and young stems.’
Outdoors, in the spring, it is not uncommon for a plant to become infested with mealybugs because a new plant that has them has been introduced nearby. Female mealybugs do not have wings but can crawl short distances, and the young nymphs can be blown by the wind from one plant to another. Ants (which are attracted to the honeydew excreted by mealybugs) can also transport these insects from one plant to another. So it is important to check the other plants in your garden for the presence of mealybugs. Look for damaged / yellowing leaves and sooty black and/or sticky deposits. Mealybugs can often be found on the underside of leaves and in the nooks and crannies of a plant, at the base of leaf petioles (or needles) and in branch crotches.
Mealybugs can be very difficult to control and get rid of, but in an otherwise healthy plant, if you can reduce their numbers, other natural predators like lady beetles, parasite wasps and lacewings can keep them at a manageable level so that plant damage is minimized. The first thing to do is to spray your yew with a hard blast of water from your hose. Repeat this every couple of days, as necessary. If the number of remaining mealybugs is small, you can pick them off and crush them. If this doesn’t remove them, you can apply insecticidal soap or horticultural oil. Be sure to follow the directions on the label.
If none of the above measures reduce the number of mealybugs on your yew to a tolerable level, you might have to consider replacing your plant. Always inspect new plants before introducing them to your garden, and consider choosing plants that are not prone to problems with insects and disease.
Good luck with your yew !