ORNAMENTALSAND
TURF
ORNAMENTALS
The information and recommendations in this newsletter are applicable to North Carolina and may not apply in other areas.
Boxwood psyllids are now emerging on American and Korean boxwood plantings. Psyllids are tiny (1 to 2 mm), green, sucking insects that resemble aphids or miniature cicadas. Boxwood psyllids overwinter as eggs inserted between the bud scales. Eggs hatch as soon as the buds begin to open and the nymphs begin to feed on the expanding foliage, removing plant sap. Feeding injury produces cupping and curling of the leaves, enclosing several nymphs in the leaf pockets. The nymphs also produce white, waxy secretions. Adults emerge in late May and June, mate and lay their eggs under the bud scales. There is one generation per year. Boxwood psyllids generally do not kill plants but can affect aesthetics and overall plant vigor. For control, early detection is essential to avoid leaf damage. Insecticides, including Orthene, Cygon, Dursban, Sevin, and insecticidal soap, are effective and should be applied as the leaves are expanding. Insecticide treatments applied after leaves have fully expanded (mid-late May) will not alleviate this year's damage, but may help to reduce psyllid numbers next year.
Boxwood leafminers can do significant damage to the foliage of boxwood, but they usually do not cause dieback. Because the boxwood leafminer has only one generation of midges per year, treating in April and May will protect the shrubs for the rest of this year. A systemic pesticide should be applied on the next convenient day. The maggots develop in blister-like galls on the current year's leaves. Heavily-infested shrubs may become discolored particularly during the winter. These shrubs also tend to defoliate prematurely. A systemic insecticide such as dimethoate (Cygon) or Orthene should give adequate control of the maggots inside the leaves. Because the boxwood leafminer appears to have acquired some resistance to dimethoate, it is a good idea to treat again in two weeks in order to increase the level of dimethoate in the new leaves to levels toxic to the insect. There is additional information on the boxwood leafminer in Ornamentals and Turf Insect Note No. 16.
The azalea lace bug is the most frequently-reported insect pest in
the landscape. Lace bugs feed by inserting their needle-like
mouthparts into leaves and injecting saliva. When the lace bug
sucks out the predigested soup, the empty cells left behind are
conspicuously pale. After what seems like a short period of time,
lace bugs cause the leaves to become completely bleached and have
a bronzed appearance. Lace bug injury is similar to, but coarser,
than thrips injury. Lace bugs also leave dark spots of excrement (fly specks) on
the lower leaf surface. This is one method of determining lace bug
damage from spider mite damage; spider mites do not leave fly
specks. Azalea lace bugs are relatively difficult to control.
Perhaps this is because the eggs are inserted into the leaf tissue
and covered with a drop of varnish-like excrement and are thereby
protected from insecticides. It is best to wait until the azalea
blooms have faded before treating with an insecticide; waiting
allows all of the overwintering eggs to hatch and avoids killing
pollinators. There is additional information on lace bug control in Ornamentals and Turf Insect Note No. 39.
Web page last updated on April 27, 1998 by Stephen J. Toth, Jr..
