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Outdoor Insects
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Elm Leaf Beetle
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
These pests have been in the United States since about 1834 and are
now widespread throughout the country, including Nebraska. They live
mainly on elm trees, the only host on which they reproduce. They
affect all types of elms, including American and Siberian (Chinese).
This is not the elm bark beetle, the pest which is notorious for
spreading Dutch elm disease.
The adult elm leaf beetle is about 1/4 inch in length, with
greenish-yellow and black stripes on the upper part of its body.
These beetles can fly. In the fall, they bunch together to
hibernate. They frequently select sites beneath leaves next to
building foundations, around windowsills, in attics and crawlspaces,
and even in outer walls.
These beetles become active as weather turns warmer in the spring.
They are a harmless nuisance indoors. Most of these pests will die
indoors within a day or two after emerging from hibernation. Those
which find their way to a newly-leafed out elm tree have a better
chance of survival.
Once on a tree, the adult elm leaf beetles lay eggs on the
undersides of leaves. Small yellow-and-black spotted larvae hatch in
late May and early June. They begin to feed, leaving only the leaf
veins. This won't kill the tree unless it occurs extensively two or
three consecutive years. After the larvae have fed on leaves for
about a month, they move down the tree trunk and pupate on the
ground around the tree.
Control is easiest at that stage, because it is usually difficult to
spray them when they are high in a large tree. Look for small yellow
pupae which resemble puffed rice around the base of the tree.
Sprays, including carbaryl (Sevin), diazinon and malathion, can be
used outdoors against elm leaf beetles. Follow label directions
carefully. Commercial applicators can also apply systemic
insecticides for elm leaf beetle control in trees. Indoors, a vacuum
clean is the best control methods.
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Lace Bugs
-by Dennis Ferraro Extension Educator Douglas/Sarpy Extension Unit
This pest affects sycamores, hackberries, elms and other trees. It
feeds on the underside of the leaves, causing yellowing. Heavy
infestations may cause the foliage to turn brown and drop
prematurely.
When lace bugs are present, there will be many small black tar-like
spots on the undersides of the leaves. The adult lace bugs, also
called tree lice, are less than 1/4 inch long. They are oblong and
whitish colored with black markings.
These pests may bite humans, but cause only momentary discomfort.
If the lace bug infestation is large, you may want to consider
chemical controls. Thoroughly spray the underside of the foliage
with carbaryl (Sevin) or acephate (Orthene). Follow label
directions.
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Leaf-curl Aphids
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
In late spring, it is common for ash trees to have aphid problems.
These small sap-sucking insects are less than 1/16 inch long. They
multiply quickly and damage plants.
The leaf-curl aphid attacks leaves from the underside, causing them
to curl inward and distorting the appearance. On an ash tree,
usually damage the newer growth at the ends of branches. Seldom is
the damage widespread or on inner leaves. If you notice distorted,
curled leaves, examine one by opening the curl and looking on the
underside. If aphids are the problem, you will notice a white sticky
substance coating the leaf.
Before using any control methods, open the curled leaves or the
insects will be protected. This may be done by hand or by using a
hard stream of water from a hose. Once curls have been opened,
thoroughly coat the underside of the leaves with insecticidal soaps
(Safer), superior oils (Sun Spray), malathion or diazinon. Spraying
may need to be repeated in 10 to 21 days. If one type of product
appears ineffective after several weeks, try a different kind of
control product. Note: The Nebraska Department of Agriculture and
UNL Cooperative Extension are installing insect monitoring traps in
many areas of the state. The traps are triangular, tent shaped and
about 10 inches long. They are bright green or white. These traps
are non-toxic to people and pets. Please do not disturb the traps.
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Lilac-Ash Borers
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
This insect effects both lilac shrubs and ash trees. The immature
insect or larvae spends most of it's time in tunnels within the
tree. It is very difficult to control this borer once it is in the
wood. Like most borers it does not stay in the part of the tree that
is responsible for food and water uptake. The mature borer larvae
overwinters and in the tree. The adult moth, which looks like a
clear winged wasp with black and yellow or orange and brown bodies
emerged the first few days of May. They leave a small pupae skin sac
attached to the hole in the bark. The moth lay eggs on the bark of
the tree.
To treat for the lilac-ash borer cover or drench the trunk and
branches of trees and shrubs with ....................from ground
level to 10 or 12 feet above ground.
When using any pesticides always read and follow label directions.
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Mimosa Webworms
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
These worms are about one half inch long, pale greenish-gray color,
with five white stripes extending down the entire length. They feed
on honeylocust and mimosa trees, causing severe defoliation,
decreasing tree vigor and making them unsightly. The webworm weaves
a nest around leaves and feeds on the interior of the web.
Spray trees with Bacillus thuringenisis (Dipel) when the browning
first appears and again in early August. You may also use carbaryl (Sevin),
diazinon, or acephate.
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Sawflies
by Dennis Ferraro Extension Educator Douglas/Sarpy Extension Unit
The adult resembles a small bee, and appears in early spring. The
female lays eggs on the current year's needles of several conifer
trees. The eggs are laid near the ends of the ends of the branch.
Upon hatching in late April to mid-May, the larvae begin to feed on
young needles.
As the larvae grow, they move inward on the branch and begin to feed
on older needles. This pest devours the entire needle, leaving only
small stubs on the branch.
When sawfly larvae are disturbed, they form an S-shape with their
bodies. Pine sawflies affect ponderosa, Scotch, Austrian and mugo
pines. These larvae are about 3/4 to one inch in length and a
uniform yellowish-green or grayish-green color. Pine sawflies feed
voraciously, and may cause severe damage to trees.
Yellowheaded spruce sawflies attack all types of spruce trees. The
larvae are 1/2 to 3/4 inch long and light yellowish-green with
several grayish-green stripes down their bodies. For this pest to
severely damage or kill a tree, it usually takes three to four
consecutive years of infestation.
Natural enemies are the best method of controlling both pine and
yellowheaded spruce sawfly larvae. Encouraging birds to feed in
infested areas is very beneficial. In minor infestations on small
trees, larvae can be picked off the tree and immersed in a container
of soapy water. Commercially-available virus products can be used to
kill sawfly larvae.
If you choose to use an insecticide, spray needles thoroughly when
sawfly larvae are first sighted in May and June. Chemicals such as
carbaryl (Sevin) or acephate (Orthene) may be used.
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Twig Girdlers
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
These borers attack oaks and other hardwood trees. In early spring,
the adult insect lays eggs on the new buds or growing points of the
tree. About 10 days later they hatch and the larvae bore into the
new growth, spiraling toward the older part of the tree. As they
move, they kill the outer twigs. Symptoms of borer activity show up
in the fall as dead leaves remaining on the ends of branches.
Removal of dead twigs will help reduce next year's twig girdler
population, because they live through the winter in those twigs.
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Uglynest Caterpillars
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
These hardwood defoliators feed on lindens, cherries, and other
popular landscape trees. The caterpillar stage is yellowish-white
with a series of small brown dots down its back and it is about an
inch long. The eggs hatch and the larvae begin to feed. They create
extensive webbing which incorporates twigs, dead leaf material and
fecal pellets. These nests may completely engulf branches or small
tress.
Remove all nests possible then apply a foliage spray such as
carbaryl (Sevin).
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Zimmerman Pine Moths
-by Dennis M. Ferraro Extension Educator Douglas/Sarpy Extension
Unit
This insect affects Austrian, ponderosa and Scotch pines. Neither
the moth or the boring larvae are commonly seen by people.
Trees infested by this pest develop golf ball-sized masses of pitch.
Active masses are pinkish colored and soft. Whitish-yellow sap may
drip from them and run down the surface of the tree trunk.
Zimmerman pine moth borers usually attack where a branch extends off
the main trunk. Affected limbs are weakened and may break off. If
you remove a clump of pitch, you will see small holes (1/8 - 1/4
inch) into the bark. A material which resembles sawdust accumulates
at the entrance of the holes. The larvae which hatch from these eggs
bore into and attack the tree in late April. The moths lay eggs
singly under bark scales near the original infestation site. Once
into the tree, the borer is very difficult to control.
Control Zimmerman pine moths by coating and drenching the trunk and
large branches of affected trees with insecticides such as Lindane.
This will be most effective if done in early to mid April when a
stage of the insect is on the surface of the bark. Chemicals
injected into the tree are controversial and show varying results.
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