ORNAMENTALSAND
TURF
ORNAMENTALS
The information and recommendations in this newsletter are applicable to North Carolina and may not apply in other areas.
Seedcorn maggot flies are grayish-brown and about one-fifth of an
inch in length. The legs are black and there are bristles
scattered on the body. Some seedcorn maggot flies become infected
with a fungus of the genus Entomophthora. Infected flies are
swollen and have pinkish bands on the abdomen. Sometimes, gray
Entomophthora spores are visible on the fly and on the substrate
nearby. This fungus apparently causes the flies to land on
protruding objects such as any dead twigs of dogwood, crape myrtle,
clothes lines, and fence posts. The flies cling there and usually
die in the afternoon as their abdomens swell with fungal strands
inside. Early the next morning, the fungal spores are released
into the air while the humidity is high. The spores infest other
seedcorn maggots. Although the fungus-infected flies appear to be
"sucking the life" out of a plant, these adult flies are harmless.
The seedcorn maggot is found throughout North Carolina. Seedcorn
maggots feed primarily on decaying organic matter, but sometimes
infest the seeds and seedlings of vegetables. The dead,
fungus-infected flies are sometimes abundant on the dead twigs of
dogwood and crape myrtle in the spring. Most of the damage is
caused by the maggot stages that sometimes kill germinating
vegetable seeds; this results in poor stands and replanting.
Injury is usually most severe during wet, cold seasons and on land
rich in organic matter. No control is necessary on dogwoods and
other ornamentals. The presence of fungus-infected flies indicates
a natural control factor at work. For control of the maggots in
vegetable gardens and field crops, shallow planting in
well-prepared seed beds sufficiently late in the season to get
quick germination of the seed is probably the best means of
control. Prompt replanting or resetting of damaged crops usually
works well. In addition, the maggots are easily controlled by
planting treated seed.
Aphid populations increase dramatically because they reproduce
parthenogenetically and because they migrate into new areas from
time to time. In warm weather, parasitic wasps, lady beetles,
syrphid fly maggots, lace wings and other predaceous insects feed
on aphids so that aphid populations often decrease rapidly as well.
Aphid populations are sometimes devastated by a fungus that infects
aphids as a sort of super athlete's foot disease. Because
ornamental plants are somewhat sensitive to pesticides, be sure to
water the plants thoroughly before spraying them and to treat them
early in the morning or late in the evening so that the pesticide
residue is dry before the plants are exposed to direct sunlight.
Insecticidal soaps and horticultural oils give good control of
aphids. There is additional information on the control of aphids in Ornamentals and Turf Insect Note No. 38.
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.
Talstar as a Flowable, GC Flowable, PL Granular, and GC Granular is
labeled for use in turf for a wide variety of pests including mole
crickets, chinch bugs, sod webworms, and cutworms. Like other
synthetic pyrethroids, low-use rates and low mammalian toxicities
are attractive features of this product. Check the label to
purchase the correct formulation for your intended use site (e.g.,
golf courses, commercial properties, residential lawns). This
product was not included in my insect control recommendations, but
is available for use.
Web page last updated on April 28, 1997 by Stephen J. Toth, Jr..
