January 2020 Marion Murray, Extension IPM Specialist • Diane Alston, Extension Entomologist
DISEASES
(Listed in Order of Importance)
Coryneum Blight (Shothole)
Importance as a Pest on Apricot: high
Other Fruit Hosts: nectarine, peach, and sometimes cherry
General Info: Shothole is a common fungal disease in Utah. It attacks dormant leaf buds, blossom buds, leaves, fruit, and twigs. The first visible lesions occur on young leaves as small, round, tan spots that eventually fall out, leaving round holes. Circular lesions develop on fruit that first appear as reddish spots, and later as rough, corky bumps. Apricots are very susceptible.
Symptoms:
round, corky or sunken spots on fruit
dead twigs
holes in leaves
dead buds that ooze gum
Management: Prune and destroy all infected plant tissue. Prevent irrigation water from wetting leaves because the water will spread spores. For severe infections, apply a copper spray in fall when 50% of the leaves have dropped to prevent infections on fresh leaf scars.
Gummosis
Importance as a Pest on Apricot: moderate
Other Fruit Hosts: all stone fruits
General Info: Gummosis is a general term describing the prolific oozing of clear sap from beneath the bark. Gumming is produced in response to a variety of conditions, including insects, diseases, and wounding. It can also be a response to poor growing conditions, such as compacted soil.
Symptoms:
gelatinous-like ooze on bark
Management: To most accurately identify the cause of gummosis, consult your local county Extension agriculture agent.
Perennial Canker
Importance as a Pest onApricot: moderate
Other Fruit Hosts: cherry, nectarine, peach and plum
General Info: Also called cytospora canker, perennial canker is caused by a fungus. Cankers are areas of dead cambium and bark and can occur on stems, limbs, and twigs. They are off-color, usually oval-shaped, and usually slightly sunken. Dark amber gum may exude from the canker edges. Cankers enlarge yearly or advance down side branches. Spores spread this fungus during wet weather, and successful infections occur in weak or wounded tissue.
Symptoms:
amber-colored ooze
flaking bark
necrotic (brown) cambial tissue just under the bark
Management: Prevent wounding of the bark from winter sunscald by applying “white tree wrap” from December to April. Also, avoid injury to bark by cats, hedge trimmers, etc. And finally, control wood-boring insects, since their damage may allow entrance of the fungus. Prune infected branches by cutting at least 4 inches below the visibly diseased wood (scrape away bark to find the edge of the canker).
INSECTS
(Listed in Order of Importance)
Greater Peachtree (Crown) Borer
Importance as a Pest onApricot: moderate
Other Fruit Hosts: nectarine, peach, and plum
General Info: The larval form of this clearwing moth damage trees by tunneling in the cambium, just below the bark, typically at the soil-line of the trunk. Backyard orchardists should look carefully for round holes near the soil-line and oozing tree sap mixed with frass (sawdust-like excrement, shown at right). Adult moths begin activity in late June and mated females lay their eggs on the base of tree trunks or upper roots. Trees may be girdled and die due to borer injury. Young trees and old or drought-stressed trees are vulnerable.
Symptoms:
ooze mixed with sawdust-like frass at the soil line
dieback of canopy
Management: Remove all weeds and tall grass from around the base of the trunk. Preventive trunk sprays (permethrin or carbaryl) is the main control tactic for conventional management. Apply once per month from early July through September, on the lower 12 -18” of trunk and exposed roots. Organic options include products containing spinosad (apply every 10 days), or the use of beneficial nematodes. (Contact your local county Extension agriculture agent for more information on the use of nematodes.)
Peach Twig Borer
Importance as a Pest onApricot: moderate
Other Fruit Hosts: nectarine, peach, and plum
General Info: In spring, chocolate brown larvae emerge from overwintering cells on the limbs of trees and then tunnel into succulent shoot tips. Infested twigs die back and small amounts of gum may exude from tunnel openings. In summer, a second generation of these “worms” enters fruit when succulent shoot growth has ceased. In backyard trees, injury may not be severe enough to require treatment every year.
Symptoms:
frass (sawdust-like excrement) on fruit
holes in fruit
dead shoots
Management: Peach twig borers activity is determined by seasonal temperatures, and the timing of activity varies from year to year. To find out when peach twig borer is active in your area of the state, and for spray recommendations, contact your local county Extension agent or subscribe to the USU IPM Tree Fruit Advisory. Conventional insecticides include pyrethroids (products ending in “thrin”), carbaryl, and malathion, and organic options include spinosad and Bt (Bacillus thuringiensis).
Spider Mites
Importance as a Pest onApricot: moderate
Other Fruit Hosts: all fruits
General Info: Mites are very small arthropods that are more closely related to ticks than insects. They overwinter as adults at the base of trees and may become a problem during hot, dry conditions in mid and late summer when they reproduce rapidly.
Symptoms:
stippled leaves due to removal of chlorophyll
loss of tree vigor
fine silk webbing that becomes apparent when populations are high
Management: Predatory mites that feed on spider mites can provide effective biological control if they aren’t harmed by pesticides. Spider mite outbreaks often follow pesticide applications that upset the predator-prey balance. If needed, mites can be managed by washing down trees or plants with a stiff spray of water, and/or applying insecticidal soap or 1% horticultural oil (both are organic). Avoid applying soaps or oils during the hot part of the day as some leaf burn may result.
Earwigs
Importance as a Pest onApricot: low
Other Fruit Hosts: all fruits, but especially stone fruits and berries
General Info: Earwigs will climb the apricot trunk and chew into fruits as they near maturity. They also feed on other insects so their presence, at times other than when fruits are ripe, is beneficial.
Symptoms:
shallow or deep holes in fruit
black dots of excrement around feeding sites
Management: Remove debris and weeds from touching the base of trees. Rolled cardboard strips tucked into limb crotches can be used to trap and remove earwigs from trees (remove and replace cardboard rolls). Another option is to wrapping the trunk with a 3” wide band of duct tape covered with tanglefoot (a sticky substance). If necessary, applying carbaryl or spinosad (organic) to the tree will provide a short interval of protection.
European Fruit Lecanium Scale
Importance as a Pest onApricot: low
Other Fruit Hosts: all fruit trees
General Info: Lecanium scale is a soft scale that has piercing-sucking mouthparts that remove plant phloem or sap. In early summer, thousands of young scales called “crawlers” emerge from under the mother scales and move to new sites to feed. Lecanium scale can build to large populations quickly if not managed. The crawler stage occurs from early July to mid-August in northern Utah.
Symptoms:
slow tree growth
yellowed leaves
leaf drop
honeydew
twig dieback
Management: In spring before leaves emerge, scrub infested limbs with a mesh dish sponge to remove adults. In addition, apply a 2% oil application when apricot buds start swelling, and apply 1% oil or insecticidal soap in early July on crawlers.
European Paper Wasp, Yellow Jackets
Importance as a Pest onApricot: low
Other Fruit Hosts: soft ripe fruit
General Info: The European paper wasp builds umbrellashaped nests in protected sites and yellow jackets build nests underground. The European paper wasp is very attracted to soft ripe fruit.
Symptoms:
holes in fruit
Management: Clean up rotting fruit on the ground and regularly pick ripe fruit. To trap European paper wasps, cut the top third of a soda bottle off and invert it into the bottom portion. Punch holes along the top edges and insert wires for hanging. Fill the bottle with 1 part fruit juice, 10 parts water, and 1 tsp detergent. Hang the trap in peach trees or nearby areas just before fruit starts to ripen, and empty and re-fill as necessary.
Apple maggot (Order Diptera, Family Tephritidae) is not currently a pest of commercial orchards in Utah, but it is regulated as a quarantine insect in the state. If it becomes established in commercial fruit production areas, its presence can inflict sub
Codling moth (Cydia pomonella; Order Lepidoptera, Family Tortricidae) is the most serious pest of apple and pear worldwide. In most of Utah, fruit must be protected season-long to harvest a quality crop. Insecticides are the main control tactic, with both
Eriophyid mites are translucent, cigar-shaped microscopic mites that cause deformities on many plants species. These mites are noticed when their feeding causes abnormalities of plant tissues such as erineum, galls, brooms, leaf curling, blisters, rusts,
The European red mite is native to Europe and was first introduced into the Pacific Northwest in the early 1900s. Since then, it has spread and become established throughout the United States and Canada. Mites are tiny arthropods, measuring less than 1/60
The fall webworm is a common defoliator of ornamental and fruit trees in Utah. Starting around late July, the caterpillars, webbing, and damage become noticeable, particularly in some of the canyons adjacent to populated areas.
Utah is home to about 1,000 named species of native bees, with several hundred species living in any one valley and adjacent montane habitats. Urbanization takes its toll on native bees, but many species can persist with a little help from gardeners and
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
Trees that are under stress or that have bark wounds are most susceptible to attack by Pacific flatheaded or flatheaded appletree borers Mature trees are not usually killed, but borer activity can weaken trees or contribute to eventual death. Newly plant
Peach twig borer (Anarsia lineatella) is found worldwide wherever stone fruits are grown. In Utah, it is a significant pest on peach/nectarine and apricot. There are typically three generations of peach twig borer in northern Utah (May-June, July, and A
The pear sawfly, which is actually a wasp, is a common pest on pear, cherry, and hawthorn in Utah. The slug-like appearance of the larval stage has prompted this insect to also be referred to as the pear or cherry slug in various parts of the country. Alt
Prionus root borers belong to a family of beetles commonly known as long-horned beetles. The larvae are often referred to as round-headed borers because their body shape is cylindrical. Several species in the Prionus genus are large, root-boring beetles,
Row covers on Utah farms. As an integrated pest management tool, row covers act as a physical barrier that prevents the movement of pests such as insects, birds, and mammals, to host plants.
Lily leaf beetle (LLB) is an exotic pest from Eurasia that causes damage to plants in the Liliaceae family. Native and cultivated Lilium and Fritillaria are sensitive to attack, including rare and endangered species. LLB can cause economic and aesthetic l
A beginner's guide to help identify common native bees in Utah, including social and solitary bees. The exotic western honey bee and bee "mimics" are also included, as well as information on human impacts on bees and what you can do to promote bee health.
[Update 8/2022: Northern giant hornet is the new common name for this pest.] Asian giant hornet is an invasive wasp that was detected in northwest Washington and British Columbia, Canada in fall 2019 and spring 2020; however, it is not known to be establi
European Cherry Fruit Fly (ECFF) is a new invasive cherry-infesting pest that is not known to occur in Utah. Host plants include cherry and honeysuckle. Heavy infestations in Europe have resulted in 100% fruit loss. Since adults fly only short distances,
The red and black imported fire ants (IFA) are an invasive and aggressive pest not known to occur in Utah, but parts of southern Utah may be suitable for colony establishment. IFA can be easily distinguished from other ants in Utah by both the varying siz
In June 2019, the samurai wasp [Trissolcus japonicus (Ashmead)] was discovered in Salt Lake City. This exotic parasitoid wasp is the most promising agent for biological control of BMSB and is uniquely evolved to lay its eggs inside of BMSB eggs. Help us p
The spotted lanternfly (SLF) is a new invasive pest from China that was first detected in the U.S. in Pennsylvania in 2014 and has since spread to other states. SLF attacks more than 100 host plants, including grapes, fruit trees, hops, and hardwood and o
Asparagus beetle and spotted asparagus beetle are leaf beetles in the family Chrysomelidae. These beetles feed exclusively on asparagus and are native to Europe. Asparagus beetle is the more economically injurious of the two species.
Mating disruption as a method to manage orchard pests became commercially available in the early 1990s, and was adopted by many Utah growers about a decade later. Use of this pest management technology c
Learn how to identify some invasive insects and their look-alikes. Here, we provide a quick identification guide for brown marmorated stink bug, Japanese beetle, emerald ash borer, and Asian longhorned beetle.
Sap beetles are typically considered a secondary pest of corn and overripe fruits and vegetables. Sap beetles are broadly identified by their small and ovular bodies and club-shaped antennae. Adult beetles feed on corn silk, pollen, and tassels. Larvae fe
“Balance of Nature.” Virtually all pest populations are affected by natural enemies to some extent. In many cases, natural enemies are the primary regulating force of the pest populations.
Degree days (often referred to as “growing degree days”) are accurate because insects have a predictable development pattern based on heat accumulation. Insects are exothermic (“cold-blooded”) and their body temperature and growth are affected by their su
BMSB was first detected in Utah in 2012; it is now established in four counties (Weber, Davis, Salt Lake, and Utah) and has been detected in two other counties (Cache and Box Elder). As an aggressive generalist herbivore, BMSB infests a broad range of pla
The campylomma bug (or mullein plant bug; Hemiptera: Miridae) causes sporadic damage in Utah apple orchards. Damage is inflicted by nymphs, which feed on developing fruit causing dimpling and fruit distortion. As apple fruits mature, they become less susc
n Utah high tunnel production, there are a variety of caterpillar pests (larvae of moth and butterfly species) that cause economic damage to crops. Common caterpillar pest species found in Utah include hornworms, tomato fruit worms, imported cabbage worms
The western cherry fruit fly (Rhagoletis indifferens, Order Diptera, Family Tephritidae) is the most important pest of sweet and tart cherries in Utah. Once the skin of fruits becomes soft enough to penetrate, adult females insert eggs with their oviposit
Damping-off is caused by several soilborne fungi including Pythium, Rhizoctonia, Fusarium and Phytophthora species. The fungi kill seedlings that are just germinating and seedlings that have been growing for several days.
Emerald ash borer (EAB) (Coleoptera: Buprestidae) is an invasive woodboring beetle that has caused the decline and mortality of tens of millions of ash trees (Fraxinus spp.) in the U.S. It is considered the most destructive forest pest to ever invade Nort
First detected in 2014 in Utah, elm seed bug is now widely distributed along the Wasatch Front and Cache Valley, and has been reported west to Duchesne County, east to Tooele County, and south to Grand County. Elm seed bug activity peaks in mid-summer whe
Several species of leafrollers are economically important pests of tree fruits in North America. In Utah, injury to tart cherry crops from leafroller caterpillars prompted a 4-year survey for five species that are known to occur in the western U.S. Pherom
Tomato and tobacco hornworms are closely related species that cause similar damage to the same host plants. Both are equivalent in size and appearance. Tomato hornworms are the larval stage of the fivespotted hawkmoth (Manduca quinquemaculata) and tobacco
This fact sheet describes the invasive Japanese beetle (JB) and lists vegetative hosts that can be affected by JB, including ornamental plants, trees, shrubs, turfgrass and vegetables. This pest can cause significant damage in high numbers. It was first d
Western conenose bug is an insect that feeds on the blood of vertebrates and can carry the parasite that causes Chagas disease of humans. This insect is present in Utah, but is not commonly found.
Powdery mildew is widespread in Utah and affects many vegetables, fruit, and landscape plants. There are several species of powdery mildew fungi, and typically they target just a single host or only hosts in related plant families.
Small hive beetle (SHB) is a pest of honey and bumble bee colonies that is native to Africa. SHB feeds on pollen and honey, kills bee brood and workers, and causes honey to discolor and ferment.
Spotted wing drosophila (SWD) is an invasive insect native to Southeast Asia; it was first detected in Utah in 2010. SWD management tactics include removing nearby alternative host plants, timely harvest of fruit, expanding the preventive insecticide prog
Spotted wing drosophila can attack fruit as soon as it begins to ripen, so that is when monitoring should begin. For example, place a trap in a cherry tree when the fruits begin to turn pink. Continue trapping for at least two weeks after harvest. Because
Thrips are a common pest that can be found on many high tunnel crops, plus hundreds of weed species. Two species commonly found in Utah include Western flower thrips and Onion thrips. Bean thrips may also occur in the state.
Velvet longhorned beetle is an invasive wood-boring beetle first detected in Utah in 2010. VLB can negatively impact fruit yield, tree longevity, and wood marketability. Prevention, monitoring, and early detection are the key management recommendations fo
Aphids are small, pear-shaped insects with piercing-sucking mouthparts that feed on plant tissue. They can be found inside high tunnels all season long.