ORNAMENTALSAND
TURF
ORNAMENTALS
The information and recommendations in this newsletter are applicable to
North Carolina
and may not apply in other areas.
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 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 until then allows all of the overwintering
eggs to hatch and avoids killing pollinators.
Boxwood
leafminers can do significant damage to the appearance of boxwood. 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. The
maggots develop in
blister-like galls on the current years leaves. Heavily infested shrubs
may become discolored, particularly during the winter. These shrubs also tend
to defoliate prematurely. For years we have recommended the systemic
insecticide dimethoate (Cygon), because it is readily available, it is labeled
for home use and boxwood leafminers, and it used to work. Evidently, at least
some populations of the boxwood leafminer have developed resistance to
dimethoate. In our demonstrations, Orthene Tree Turf and Ornamental 75% SP and
Merit 75% WP have both given good control of this leafminer when injected into
the soil or applied as a drench. Merit is labeled and useful for this pest; how
ever, it is quite expensive (a 2 ounce container costs $50 plus
). Merit is not a restricted use pesticide. Only the cost
will restrict its use. The homeowner formulation of Orthene (9.4% EC) is
sufficiently labeled for us to recommend its use (i.e., shrubs and leafminers). Although we
did not include the homeowner formulation in our demonstrations, there is no
reason to think that it would not give adequate control.
Several greenhouse operators have complained of western flower thrips damaging flower crops in the past few weeks. The western flower thrips has acquired resistance to a variety of pesticides and is a double threat to ornamental plants because it can also transmit impatiens necrotic spot virus and tomato spotted wilt virus. The western flower thrips can overwinter successfully in North Carolina as well as areas further south. One threat to greenhouse plants is that western flower thrips in South Carolina and Georgia may pick up tomato spotted wilt virus there, blow into North Carolina and be sucked into greenhouses where they can then spread the virus among susceptible crops. Another threat is that western flower thrips may blow into greenhouses and become established (because of its pesticide resistance); later a plant with impatiens necrotic spot virus may be brought in and the virus acquired by immature western flower thrips which spread the disease through the rest of their range.
Avid is the most effective pesticide for western flower thrips management
(it is moderately effective). Several applications are necessary for good
suppression. Other pesticides labeled for thrips management in the greenhouse
include chlorpyrifos (Duraguard, a new microencapsulated formulation from
Whitmire that is less phytotoxic than the older chlorpyrifos formulations).
Carzol (which has a 24(c) registration in North Carolina) is also effective,
but has a very high oral toxicity for humans. Both chlorpyrifos and Carzol
are somewhat effective for western flower thrips management. The advantage
of using Avid is that it would also control the broad mites. The agricultural
formulation of Dibrom is labeled for thrips suppression on greenhouse ornamental
s. Dibrom is phytotoxic as a spray and as a thermal fog, but Dibrom can be
applied as a smoke from a hot plate. The hot plate can be set up on a timer
so the fumigation takes place after working hours. Set the hot plate to 160
degrees F. The greenhouse must be ventilated the next morning before reentry.
The most abundant of the cicadas that will emerge in the foothills of North
Carolina is the seventeen year cicada. The last time this insect
emerged was 1979; the next time will have to worry about seventeen year cicadas
will be in 2013! People are already noticing the holes the
nymphs make for their emergence in late May or early June. If the soil is
muddy, the nymphs even forms small chimneys or "turrets." The only real
damage cicadas do is during oviposition as females jab their eggs
into small stems. These stems die and eventually drop to the ground. Many
people have a low threshold for tolerance of billions of loud, shrill insects
buzzing in the trees. Fortunately they only sing during the day! Because the
seventeen year cicada is not wary, it does not try to escape from predators.
They are tasty to birds, mice, raccoons, foxes, dogs and other animals.
Occasionally dogs eat the cicadas until they become ill. Sevin is labeled for
cicada management.
Web page last updated on 22 April 1996 by Stephen J. Toth, Jr..
