Landscape Ornamental Insects
Aspen, Important Pests of Ornamental Aspen
Aspens are one of the more popular forest trees in the Intermountain West. They add
a brilliant yellow glow to the collage of fall colors. In an attempt to enjoy these
beautiful trees around the home environment, many well-intentioned homeowners purchase
or otherwise acquire aspens and transplant them into their landscapes.
Bark beetles are one of the most destructive forest pests in the world. They are different
than the larger longhorned and roundheaded/metallic woodboring beetles commonly infesting
the inner wood of trees.
Boxelder bugs are a common nuisance insect to many homeowners. Although boxelder bugs
are active throughout the summer, many people don’t notice them until they start “sunning”
themselves on structures, particularly the southern-facing walls.
Boxelder leafroller damage results from larval feeding activities on the leaves. Young
larvae form webs along folds and veins of the leaves and consume the tissue between
the veins. Older larvae roll individual leaves and may web several leaves together.
Brown Marmorated Stink Bug
Brown marmorated stink bug (BMSB) is an invasive insect pest from eastern Asia. In
Utah, it was first detected in 2012 in Salt Lake City. Its broad host range includes
fruit, vegetable, ornamental, and field crop plants; in Utah, it has primarily infested
ornamental deciduous trees and shrubs in urban and residential landscapes.
Bumble Flower Beetle
Bumble flower beetles are common throughout the growing season on flowers, oozing
sap, and other sweet, overripe, or fermenting matter. Bumble flower beetles seldom
warrant the use of chemicals for control. Control methods include removing organic
material from near affected plants, and hand removal of the adult beetles from plants.
Cankerworms, also known as inchworms, are in the order Lepidoptera and family Geometridae. Geometrid moth adults have slender bodies and relatively large, broad forewings.
Both fall and spring cankerworms occur in Utah, with the fall cankerworm being most
The larval stage of the carpenterworm, Prionoxystus robiniae is a wood-boring insect that affects various ornamental trees. Unlike most other
wood-boring pests of ornamentals, which are mostly beetle larvae, the carpenterworm
is a caterpillar belonging to the moth family Cossidae.
Centipedes are predatory relatives of the insects, and are considered beneficial.
Occasionally, centipedes enter homes and become a nuisance, but management options
are available. Centipede bites on humans are rare.
Chinch bugs are occasional pests of turfgrass in Utah. Chinch bugs feed on a variety
of turfgrass species including Kentucky bluegrass, perennial ryegrass, the fescues,
bentgrass and zoysia grass. Damage is usually heaviest in sunny locations during hot,
Community-wide Grasshopper Control
Springtime, while grasshoppers are still nymphs, is the best time for communities
or neighborhoods to work together to suppress grasshopper populations. Treating as
wide an area as possible is the key to success.
Crickets will eat almost anything, including fabrics, other insects (dead or alive),
food products, and furs. Occasionally crickets may enter the home or chirp near the
home, and become a nuisance. Regular sanitation around the exterior of the home will
discourage cricket infestations.
Elm Bark Beetles and Dutch Elm Disease
Two major bark beetle species attack elm trees in Utah; both can transmit Dutch Elm
Disease (DED) , leading to tree death, decline, or chronic stress. Preventive treatments
such as foliar insecticide applications, severing root graphs between trees, injectable
fungicides, and proper pruning of affected areas can minimize transmission of DED.
Emerald Ash Borer
The Emerald Ash Borer (EAB) is a recent invasive pest, and is considered to be one
of the most destructive forest insects to ever invade the U.S. EAB adults are very
good fliers, but new infestations are primarily caused by people moving wood from
Eriophyid Mites, bud, blister, gall, and rust mites
Eriophyid mites cannot be seen without a 20x hand lens or greater magnification. Eriophyid
mites seldom cause serious injury or stress to plants; damage is normally aesthetic.
Damage from eriophyid mites usually consists of leaf galls, bud or flower galls, blisters,
scabbing, and deformities of leaves, stems, buds, and flowers.
The European earwig is an omnivore; it feeds on detritus, fungi, plants, and insects.
Earwigs can injure the buds, leaves, flowers, and fruits of a broad range of plants,
including fruits, vegetables, and ornamentals; they can be a nuisance pest by entering
Fall webworms are a common pest in urban and forest areas from mid July through August.
Fall webworms can feed on over 100 species of trees, but cottonwood and chokecherry
are preferred hosts. While unsightly, fall webworm damage rarely causes serious stress
to trees and control is usually not recommended
Flatheaded Borers (Pacific, Appletree)
Pacific flatheaded and flatheaded appletree borers are two wood-boring pests of many
fruit and ornamental trees. The most susceptible trees are drought-stressed, newly
planted, or those with trunk or limb wounds. Maintaining tree health is key to preventing
Greater Peachtree Borer
Greater peachtree borer is an important pest of peach, nectarine, apricot, cherry,
and plum. Adults are clearwing moths and larvae are caterpillars that burrow and feed
in the cambium beneath the bark near or just below the soil line. Severe larval feeding
can girdle and kill trees.
Invasive Insect Look-alikes: Mistaken Identity
Pest identification is the cornerstone of integrated pest management, but is a skill
that can be difficult to master. Mistakes in identification are common, as many insects
look and act alike, and/or can cause similar injury.
Japanese beetle was initially detected in Orem, Utah, in July 2006. Eradication efforts
have been highly successful. Adults have a broad host range (over 300 plant species)
and can cause significant damage.
Leafhoppers in the Home Garden
Leafhoppers are common problems in home gardens and orchards throughout the state
of Utah. There are many species of leafhoppers, several of which attack apples, roses,
grapes, and potatoes. Most species overwinter in the egg stage in the bark of the
host plant or among the fallen host plant leaves.
Lilac-ash borer, a clear-wing moth common in Utah, can be a destructive pest of many
species of ash, privet, lilac, and related species. Adults emerge from host trees
and lay eggs in the spring; larvae feed on wood within branches, overwinter in the
heartwood, and emerge as adults the following spring.
The locust borer occurs in eastern Canada and in most of the United States, wherever
its host, black locust, grows. For the past 35 years, locust borer has spread and
damaged black locust in the Wasatch Front and northern Utah. Honey locusts or other
trees are not affected by this species, whose only host is the black locust.
The oystershell scale belongs to a group of insects called the armored scales. The
adult insect is enclosed in a shell made up of its own shed skins and waxy secretions.
Under this covering is a sac-like animal that is quite different in appearance from
most insects. It has no legs, eyes, or antennae.
Pear sawfly hosts include pear, cherry, hawthorn, plum, buttonbrush, Juneberry, mountain
ash, cotoneaster, and quince. There are 2 generations of pear sawfly each year; second
generation larvae cause the majority of the damage. Damage from pear sawfly feeding
rarely warrants control.
The poplar borer is the most commonly submitted wood borer found in aspens and other
poplars in Utah. While large trees are seldom killed by this pest, it can cause the
decline of trees, weakening of branches or the bole (which promotes wind breakage),
and allows the introduction of pathogens.
Poplar Bud Gall Mite
The poplar bud gall mite belongs to the eriophyid mite family. These mites are microscopic
and about one-fourth the size of a spider mite. Adults are about 0.2 mm in length,
reddish in color, and spindle-shaped. Like other eriophyid or gall mites, this species
is most easily recognized by its host plants and characteristic damage.
Prionus Root Borer
This long-horned beetle is native to western North America and lives for 3 years or
more underground, feeding on tree roots. Severe infestations can cause the death of
stone fruit trees. In northern Utah, the rootborer is found most commonly in sweet
cherry and peach orchards growing in sandy soils.
San Jose Scale
San Jose scale is a sporadic pest in well maintained commercial fruit orchards. Severe
infestations can kill limbs, cause deformed and poor colored fruit, reduce yields,
and eventually kill trees. Monitor fruit during picking and packing (check cull bins),
and check tree limbs during pruning for signs of scale and injury.
Soft Scales in Utah
There are more than 1,000 different species of soft scales found throughout the world.
Less than 5% are considered serious pests. Soft scales feed on a wide range of woody
ornamental plants and often go unnoticed until they stunt growth or cause severe plant
Speckled Green Fruitworm
Fruitworms chew holes in fruits and leaves, and can cause localized defoliation of
fruit trees. Fruitworms can be monitored with beat-samples (abrupt shaking of tree
branches over a tray). Applications of reduced-risk insecticides, such as Bacillus
thuringiensis (Bt) and spinosad formulations, are effective for control.
Spruce Health in Utah Landscapes
Spruces tend to prefer abundant moisture and may not do well on droughty sites. Water
stress caused by too little soil moisture or too much heat can predispose spruces
to insect attack. 80% of spruce trees submitted to the UPPDL are diagnosed with stress
due to abiotic conditions such as drought stress and deep planting.
Thousand Cankers Disease of Walnut
Thousand cankers disease is caused by the fungus Geosmithia morbida. It is transmitted
by the walnut twig beetle (Pityophthorus juglandis). Once symptoms are visible, trees
can die within 2 to 3 years.
Web Spinning Spider Mite
Spider mites feed on a wide range of plants, including fruit trees, field and forage
crops, ornamentals, and weeds. Adult and immature mites feed on leaves causing white
stippling, bronzing, and defoliation. Tree vigor and fruit color, size, and production
can be reduced.
White Apple Leafhopper
White apple leafhopper is an indirect pest with two generations per year. Decision
for control should be based on economic justifications as well as orchard and other