The most common
and readily noticed sign of taxus mealybug presence on the yew is
sparse yellow foliage covered with sooty mold. The taxus mealybug
occurs on stems and branches, and tends to cluster in the forks
of branches. They overwinter as nymphs, which become active in the
latter half of May; by early summer adult females begin giving birth
to live young. There are two or three generations per year. The
taxus mealybug has been reported on other plants such as apple,
cedar, linden and maple, but is not known to reproduce on these
controls will be more effective if the mealybug population on a
plant is first physically reduced by pruning out heavily infested
and sickly branches. In some cases, large mealybugs can be scrubbed
off with a brush. Horticultural oil sprays kill primarily by smothering,
so they will be less effective against mealybugs crowded together
or occurring in layers on the plant. Horticultural oil sprays kill
all stages of mealybugs that are present at the time of application.
Most trees and shrubs can tolerate application of light (summer)
oil even during the summer months. Refer to the product label for
guidelines on plant sensitivity and any temperature restrictions.
Oil products labeled as summer, superior or Volck oil are of the
highest grade and may be used on tolerant plants during either the
growing season or the dormant season, but at different spray concentrations.
soaps provide another alternative. They are effective against both
active and settled crawlers. Oils and soaps are relatively non-toxic
and are especially good choices for areas where people are present
soon after treatment. Because of their short residual life, they
help to conserve beneficial species.
to oil or soap sprays are contact insecticides applied during the
growing season when the crawler stages of the mealybugs are present.
The presence of crawlers can sometimes be determined by sharply
tapping an infested twig or branch over a white paper. Crawlers
may be orange, brown or purple, and appear as moving specks of dust.
Because of their waxy protective covering, other stages of mealybugs
are not readily controlled by contact insecticides. Contact insecticide
sprays will not reach crawlers that have settled under old scales.
Most garden centers carry a number of insecticides registered for
mealybug control. Although resistance to insecticides may occur
in some cases, failure of contact sprays is more often the result
of not timing the applications to coincide with crawler activity.
Thus, horticultural oils are often the most effective control. In
all cases, thorough spray coverage is essential for good control.
from Lee Townsend, University of Kentucky College of Agriculture,
1999. Photo from the
Virginia Cooperative Extension.