Category Archives: Insect

Odorous House Ants

Odorous house ants (Tapinoma sessile) can be found across the United States and are one of the most common ants found in and around structures in Wisconsin.  These ants are known for their fondness for sugary foods and their distinctive odor when crushed.

An odorous house ant.  Photo courtesy of April Nobile (CASENT0005329,
An odorous house ant. Photo courtesy of April Nobile (CASENT0005329,

Appearance:  Odorous house ant adults are dark brown to black and approximately 1/8 inch long.  Their waist (petiole) has a single flattened node, which may be difficult to see because it is obscured by other body parts.  They also have 12-segmented antennae that lack a distinct club.  Odorous house ants smell like rotten coconut or blue cheese when crushed.

Biology:  Odorous house ants forage day and night, following well-established trails.  Around buildings, they often follow the edges of siding, deck boards, and door frames.  Odorous house ants are particularly fond of sugary materials such as honeydew (the feces of aphids or soft scales), and sugary foods and beverages.  Occasionally, they will feed on insects (both dead and alive) or on other items such as pet food.

Odorous house ants prefer to nest in moist areas and often create a network of interconnected nests consisting of thousands of workers and many queens.  Outdoors, they can nest in mulch beds, beneath stones or pieces of wood, under the loose bark of trees, and beneath a variety of man-made objects.  Indoors, odorous house ants can nest in wall voids and attics, in areas with damp wood or insulation, and near plumbing fixtures or vents.  When a nest is disturbed, odorous house ants can quickly relocate to another sheltered spot.  They establish new colonies after mating flights (swarms) in late spring and early summer.  Colonies can also divide in a process known as “budding”, where a queen will leave a nest with a group of workers and establish a colony in a new location.

Control:  Make sure you properly identify ants before attempting control.  Knowing the type of ant provides clues about their biology and habits, which helps in the selection of the most appropriate management options.

During warmer months, odorous house ants foraging indoors often come from outdoor nests.  Keeping plants and dense mulch away from building foundations can reduce this indoor activity.  When you see odorous house ants indoors, watch their movement, and try to track them back to where they are entering the building.

An odorous house ant colony in a “hide-a-key” rock stored outdoors
An odorous house ant colony in a “hide-a-key” rock stored outdoors

Sealing these entry points may take care of the problem.  If you can track the ants back to an outdoor nest, you can treat the nest with an aerosol or liquid ant control product (available at a hardware store or garden center).  However, because odorous house ants can have many interconnected nests, treating a single nest may not fully eliminate the problem.  Additional monitoring and treatments may be needed.

If an odorous house ant nest is indoors in an inaccessible spot such as a wall void, baits may be the best control option.  Odorous house ants usually respond well to sugar-based baits (available at a hardware store or garden center).  The ants collect the bait and take it back to the colony where the materials in the bait can kill the queen, thus eliminating the nest.  Place the bait near the foraging trails of the ants.  DO NOT apply other insecticides (e.g., spray insecticides) near the bait, as this can reduce its effectiveness.  After setting out the bait, you may notice an increase in ant activity as additional members of the colony are recruited to collect the material.  Continue to monitor the area, setting out fresh bait as needed, until ant activity fully subsides.

If your odorous house ant problem is extensive, consider consulting a pest control professional with experience in managing ants.  These professionals have additional treatment options and techniques not generally available to homeowners.

For more information on odorous house ants:  Contact your county Extension agent.


Lily Leaf Beetle – Pest Alert

The lily leaf beetle (LLB), Lilioceris lilii, also known as the red or scarlet lily beetle, is an invasive insect of Eurasian origin.  This insect was first reported in North America in eastern Canada during World War II and was most likely introduced in shipments of plant materials from Europe.  LLB spread to New England in the 1990’s and has been moving westward since that time.  LLB made its first appearance in Wisconsin in 2014 and as of early 2021 has been found in 21 counties including Brown, Calumet, Clark, Dane, Door, Langlade, Lincoln, Marathon, Milwaukee, Oneida, Outagamie, Pierce, Portage, Price, Shawano, Taylor, Vernon, Vilas, Waukesha, Waupaca and Wood Counties.

Severe feeding damage from lily leaf beetles on a lily plant (left) and an adult lily leaf beetle (right). Photos courtesy of Leslie J. Mehrhoff, University of Connecticut,
Severe feeding damage from lily leaf beetles on a lily plant (left) and an adult lily leaf beetle (right). Photos courtesy of Leslie J. Mehrhoff, University of Connecticut,

LLB can cause significant damage to true lilies (Lilium spp.), including both native and cultivated types, as well as fritllaries (Fritillaria spp.).  LLB can also cause damage, but to a lesser extent, to lily of the valley (Convallaria majalis) and Solomon’s seal (Polygonatum spp.).  LLB does not cause damage to daylilies (Hemerocallis spp.), canna lilies (Canna spp.) or calla lilies (Calla palustris).

Appearance:  LLB adults are bright red and approximately 1/4 inch long, with black legs, head, antennae, and undersides.  When disturbed, LLBs tumble from plants and land upside down on the ground, where they play dead.  Their dark-colored undersides make them hard to spot.  To potentially deter predators, adults squeak if squeezed.

LLB larvae have plump, squishy bodies and are slug-like in appearance.  They tend to be orange or yellowish in color with black heads.  At maturity, larvae can be almost 1/2 inch long.  As a defensive tactic, larvae typically camouflage themselves with their own excrement and can resemble slimy greenish-brown slugs or a mobile pile of animal droppings.

LLB eggs are tiny (less than 1/10 inch long) and reddish in color.  Female LLBs lay the eggs (typically in a batch of a dozen or less) on the underside of leaves in a row parallel to a vein.

Symptoms and Effects:  Both LLB adults and larvae chew irregular holes and notches in lily leaves, stems, and developing buds.  Larvae are the more damaging stage of the insect.  When feeding damage is severe, LLBs can completely defoliate plants and destroy flowers.

Life Cycle:  There is a single generation of LLBs each year, but adults can live for several years.  LLBs overwinter as adults in sheltered places, soil, and plant debris in gardens and wooded areas.

These overwintering sites are not necessarily near lilies or other host plants.  Early in the spring, LLB adults emerge to feed, mate and lay eggs.  Because they are strong fliers, LLBs can disperse over long distances to locate host plants.  Eventually, females lay between 250 and 450 eggs.  Eggs hatch within four to eight days.  Emerging larvae feed for two to three weeks during the spring and early summer.  Engorged larvae eventually drop to the soil to pupate (i.e., transform into adults).  Pupae are bright orange and encased in a white cocoon with black spots.  Adults emerge 16 to 22 days later and feed throughout the rest of the growing season and into the fall.

Lily leaf beetle eggs (left) and a lily leaf beetle larva camouflaged with its own feces. Photos courtesy of Gail Hampshire (left) and Kenneth R. Law, USDA APHIS PPQ,
Lily leaf beetle eggs (left) and a lily leaf beetle larva camouflaged with its own feces. Photos courtesy of Gail Hampshire (left) and Kenneth R. Law, USDA APHIS PPQ,

Control:  If you have a small number of lilies, consider hand-picking and crushing adults and larvae or knocking them into a container of soapy water.  Also, crush eggs by hand if you see them.  Repeat this process regularly throughout the growing season.  If LLB becomes a chronic and severe problem, consider replacing your lilies with plants that are not attacked by the insect.

You can also use conventional and organic insecticides to help protect plants from the LLB.  Conventional insecticides containing carbaryl, cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, permethrin, and zeta-cypermethrin control a broad range of pests, including LLB.  Organic insecticides containing azadirachtin, pyrethrins, or spinosad can also be used, as well as horticultural oils and insecticidal soap.  Make sure that the product that you select is labelled for use on landscape flowers.  Be aware that conventional and organic insecticides can pose risks to pollinators, so follow all directions on the label to minimize risks to bees and other pollinators.

For more information on lily leaf beetle:  Contact your county Extension agent.

Homeowner Guide to Emerald Ash Borer Insecticide Treatments – Pest Alert

Emerald ash borer insecticide treatment considerations.  Several insecticide products are available to homeowners for control of emerald ash borer (EAB).  Since the presence and infestation level of EAB is quite difficult to determine at early stages of an infestation, insecticide treatments may be merited to mitigate damage by EAB.  However, not all ash trees should be treated as some may be too extensively compromised or in poor condition to receive treatment.  Tree location, value, and health, as well as the cost of treatment are all factors to consider.  Due to the expense of yearly insecticide treatments, one should consider the value of a particular ash tree in relation to insecticide treatment costs before making any treatments.  In addition, consider the health of each tree before treating.  Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50% canopy thinning.  Insecticide treatments are not suggested for trees with greater than 50% canopy thinning.  Trees with greater than 50% canopy thinning should be removed and handled in accordance with local guidelines.  For a more detailed discussion on this topic, see University of Wisconsin Garden Facts XHT1215, Is My Ash Tree Worth Treating for Emerald Ash Borer.

Emerald ash borer insecticide treatment options.  Insecticide products available for use by homeowners are summarized in Table 1.  They include:

  • ACECAP 97 Systemic Insecticide Tree Implants (acephate)
  • BioAdvanced 12 Month Tree and Shrub Insect Control (imidacloprid)
  • BioAdvanced 12 Month Tree and Shrub Protect & Feed (imidacloprid)
  • BioAdvanced 12 Month Tree and Shrub Protect & Feed II (imidacloprid + clothianidin)
  • Bonide Annual Tree & Shrub Insect Control with SYSTEMAXX (imidacloprid)
  • Compare N Save Systemic Tree & Shrub Insect Drench (imidacloprid)
  • Ferti-lome Tree and Shrub Systemic Drench (imidacloprid)
  • Monterey Once a Year Insect Control II (imidacloprid)
  • Several other products containing imidacloprid are also currently available

Most of the products available to homeowners are systemic insecticides containing imidacloprid and are applied as soil drenches around the base of an ash tree.  A few granular products are also available.  Recent university research suggests that applications of imidacloprid should be made in spring to be most effective.  Research also has demonstrated that soil applications of imidacloprid-containing homeowner products provide excellent EAB protection for ash trees that are less than about 47 inches in circumference [i.e., 15 inches in diameter at breast height (DBH)].  Due to differences in application rates and label restrictions, treatment by a tree care professional (e.g., arborist) may be the best option for larger trees.  For best results, treatment of trees should begin before trees become infested.  Lastly, insecticide treatments must be repeated each year to maintain the health of ash trees.

Be aware that many insecticide products available at hardware stores and garden centers look alike.  Carefully check all product labels before purchase to make sure that you have selected the correct product/active ingredient.  ALWAYS read and follow the pesticide label directions on the product that you select!

Finally, note that although ACECAP 97 Systemic Insecticide Tree Implants are available to homeowners, we do NOT recommend that homeowners use these because they require physically drilling into a tree during their application.

Table 1

Emerald ash borer insecticide treatments available to homeowners

Product Active Ingredient Timing Type of application
BioAdvanced 12 Month Tree & Shrub Insect Control (D)

BioAdvanced 12 Month Tree & Shrub Protect & Feed (D or G)

Bonide Annual Tree & Shrub Insect Control with SYSTEMAXX (D)

Compare N Save Systemic Tree & Shrub Systemic Insect Drench (D)

Ferti-lome Tree & Shrub Systemic Drench (D)

Monterey Once a Year Insect Control II (D)

Imidacloprid Mid-April to mid-May Soil Drench (D)


Granular (G)

BioAdvanced 12 Month Tree & Shrub Protect & Feed II (D or G) Imidacloprid



Mid-April to mid-May Soil Drench (D) or Granular (G)
ACECAP 97 Systemic Insecticide Tree Implants Acephate Mid-May to mid-June Trunk Implant

Other emerald ash borer treatment options.  Homeowners may also contact a certified arborist or certified pesticide applicator to treat their trees.  See for a list of certified arborists in Wisconsin.  Professionals have access to some products that are not available to homeowners.

The University of Wisconsin does not endorse commercially available insecticide products over those available directly to homeowners.  Products discussed in this fact sheet have been evaluated in university research tests on EAB.

For more information on controlling emerald ash borer:   See:, or or contact your county Extension agent.

Viburnum Leaf Beetle – Pest Alert

The viburnum leaf beetle (VLB), Pyrrhalta viburni, is an invasive insect that feeds exclusively on and can significantly damage Viburnum species.  VLB is native to Europe and was detected in Canada in 1947.  The first report of VLB in the United States was in New York State in 1996.  VLB is now found scattered across much of the northeastern US.  In Wisconsin, an isolated infestation of VLB was discovered in Dane County in 2009, but was successfully eradicated.  In 2014, VLB was detected on a mature viburnum bush in northern Milwaukee County and other nearby infestations were detected in June 2015.  As of early 2021, VLB infestations have been found in 12 Wisconsin counties, including Brown, Dane, Iron, Kenosha, Milwaukee, Ozaukee, Racine, Sheboygan Walworth, Washington, Waukesha, and Winnebago Counties.

Viburnum leaf beetles adults (left) and larvae (right). (Photos courtesy of Paul Weston, Cornell University,

Appearance:  Adult VLB’s are approximately ¼ inch long and yellowish-brown in color.  VLB larvae can be up to ⅓ inch long and range in color from yellowish-green to light brown with a series of black spots and dashes on their bodies.

Symptoms and Effects:  VLB larvae chew holes in viburnum leaves in the spring creating a lace-like (i.e., skeletonized) pattern.  VLB larvae feed individually or in small groups and can cause significant damage to viburnum shrubs.  This damage can resemble the feeding damage of Japanese beetles (see University of Wisconsin Garden Facts XHT1062 “Japanese Beetle”).  In late June and early July, VLB adults begin to feed, chewing oblong holes in leaves.  Severe VLB infestations can cause complete defoliation of a viburnum shrub, which weakens the plant over time and can eventually lead to death.

Life Cycle:  There is only one generation of VLB per year.  VLB’s overwinter as eggs and development from eggs to adults takes approximately eight weeks.  Larvae typically appear in early to mid-May and feed for several weeks, passing through three stages (instars) as they grow.  In early to mid-June, larvae pupate in the soil and adults emerge by late June or early July.  VLB females lay eggs during the summer and into October.  They chew small pits in twigs, deposit five to eight eggs into each pit, and then cover the pits with tiny pieces of chewed wood to protect the eggs.  Each female can deposit up to 500 eggs.  Eggs remain in place through the winter until they hatch the following spring.


Cultural:  When selecting viburnum plants for the landscape, DO NOT use arrowwood viburnum (Viburnum dentatum), European cranberrybush viburnum (Viburnum opulus), or American cranberrybush viburnum (Viburnum opulus var. americanum) as these types of viburnums are strongly preferred by VLB.  Instead use resistant viburnums such as doublefile viburnum (Viburnum plicatum f. tomentosum), Judd viburnum (Viburnum x juddii), or Koreanspice viburnum (Viburnum carlesii).  In addition, between October and the following spring, examine viburnums for twigs where VLB’s have laid their eggs.  Prune and destroy these twigs to reduce VLB numbers.  During the growing season encourage natural VLB predators in your area (e.g., lady beetles, spined soldier bugs, assassin bugs, green lacewings) that can reduce VLB numbers.

Adult viburnum leaf beetle feeding damage (left) and egg-laying sites (right). (Photos courtesy of Paul Weston, Cornell University, and Bruce Watt, University of Maine;
Adult viburnum leaf beetle feeding damage (left) and egg-laying sites (right). (Photos courtesy of Paul Weston, Cornell University, and Bruce Watt, University of Maine;

Chemical:  Prior to bud break, apply horticultural oil to twigs where VLB eggs have been laid.  This will significantly reduce the number of eggs that will hatch.  Control any surviving larvae with contact insecticides such as acephate, bifenthrin, carbaryl, cyfluthrin, deltamethrin, lambda-cyhalothrin, and permethrin.  Horticultural oil, insecticidal soap, pyrethrins and spinosad can also be effective.  To achieve the best results, apply insecticides when larvae are small and before they have caused significant damage.  VLB adults can be managed with contact insecticides, if needed, but are mobile and more challenging to control.  Systemic products (e.g., clothianidin and imidacloprid) applied as soil drenches can also be effective, but apply these products after flowering (to minimize any risks to pollinators), but before VLB damage occurs to achieve the best protection.

For more information on viburnum leaf beetle: Contact your county Extension agent.


Fleas are parasites of many animals including cats, dogs, rodents, birds, and bats.  Cat fleas (Ctenocephalides felis) are the most common fleas that infest homes and attack humans, although cats, dogs and some wild animals (e.g., raccoons and opossums) are their primary hosts.  Unlike most fleas, cat fleas remain on their host throughout their entire life cycle.  Although fleas are capable of transmitting disease-causing organisms to humans, this rarely occurs in Wisconsin.  Fleas more commonly transmit tapeworms to cats and dogs.

Cat fleas are brown and flattened, and have large hind legs (see arrow).
Cat fleas are brown and flattened, and have large hind legs (see arrow).

Appearance:  Adult cat fleas are brown, flat and wingless, have large hind legs adapted for jumping, and are less than 1/8 inch in length.  Larval cat fleas are about 3/16 inch in length and resemble tiny, white, hairy caterpillars.  The presence of dried blood and dark reddish-brown or black flea excrement (i.e. flea ‘dirt’) may be the first noticeable clue that a pet has fleas.

Symptoms and Effects:  Fleabites on human skin may result in raised, red bumps that itch.  These symptoms may persist for five days or more.  Bites found on humans are typically in clusters on lower legs.  Some people are resistant to fleabites and may not notice their presence.  Other people, as well as pets, may experience fleabite allergic dermatitis, resulting in more intense itching, hair loss and reddening.  Scratching these areas may result in secondary infections.

Life Cycle:  Adults fleas lay approximately 20 to 50 eggs per day on their host.  Eggs may fall from the host and survive in carpeted surfaces.  Eggs hatch into larvae within one to 12 days.  Larvae molt three times over a period of seven to 15 days, then spin cocoons and develop into adults.  Larvae avoid light and require humidity above 75%.  Unfavorable temperatures and humidity may extend larval periods to six months or longer, and pupal periods to 12 months or longer.  Adult emergence is stimulated by noise or vibration indicating the presence of a potential host.  Typical emergence cues include vacuuming or being walked upon.  Adults fleas live for one to 12 months.  Under optimal conditions, the cat flea life cycle spans approximately 18 to 40 days.  Cat fleas may be found year-round, but are more prevalent during spring and summer due to more optimal temperatures for larval development.  Adults feed on blood using sucking mouthparts.  Larvae feed on a combination dried blood and excrement (called flea “dirt”) that accumulates in pet resting areas.  Adults may survive for weeks without a blood meal, but females require a blood meal from a non-human host before laying eggs.


For pets:  ALWAYS consult your veterinarian before selecting a specific treatment product, as different breeds of cats and dogs have different tolerances to particular active ingredients.  In general, topical, oral or flea collar applications of insecticides provide better flea control than shampoos, dips, powders, or sprays.

Flea ‘dirt’ (a combination of dried blood and excrement) indicates a flea problem.
Flea ‘dirt’ (a combination of dried blood and excrement) indicates a flea problem.

Apply topical chemicals carefully.  Follow label directions and apply where pets are unable to lick (e.g., the nape of neck or between shoulder blades).  Effective topical pet treatments (available over the counter) commonly contain active ingredients such as fipronil, imidacloprid, indoxacarb, permethrin, or selamectin.  Effective oral products contain active ingredients such as afoxolaner, fluralaner, lufenuron, nitenpyram, sarolaner, or spinosad.  Flea collars contain insect growth regulators such as methoprene or insecticides such as flumethrin, imidacloprid, or tetrachlorvinphos.  Ineffective flea treatments include vitamin B1 or yeast supplements, herbal collars and ultrasonic devices.

For home:  Indoor areas should be regularly and thoroughly vacuumed.  In addition, chemical treatments may be needed.  Common indoor flea treatment products contain pyrethroid insecticides such as permethrin, β-cyfluthrin, or deltamethrin.  Products containing pyrethrins also may be used, although these products are contact insecticides with little residual effect.  Products containing insect growth regulators (e.g., pyriproxyfen) are also available.  These ingredients prevent eggs from hatching and kill larvae, but do not kill adult fleas.  When treating, target areas such as carpets, furniture crevices, pet beds and any other areas frequented by pets.  DO NOT use foggers (often referred to as bug “bombs”), as these are generally ineffective against fleas.

If you have a flea problem, but have no pets, then you may have wild animals (e.g., raccoons, opossums or squirrels) nesting in an attic, fireplace or crawlspace.  Seek out these areas for possible treatment.  Although breeding flea populations outside of homes are rare in Wisconsin, such populations can potentially occur in pet resting areas, animal nests or sand or gravel areas in the landscape.

For more information on fleas:  Contact your county Extension agent.

Professional Guide to Emerald Ash Borer Insecticide Treatments – Pest Alert

Emerald ash borer insecticide treatment considerations.  A variety of insecticide products and application methods are available to professionals for control of the emerald ash borer (EAB).  Since the presence and infestation level of EAB is quite difficult to determine at early stages of an infestation, insecticide treatments may be merited to mitigate damage by EAB.  However, not all ash trees should be treated as some may be too extensively compromised or in poor condition to receive treatment.  Due to the expense of yearly insecticide treatments, one should consider the value of a particular ash tree in relation to insecticide treatment costs before making any treatments.  In addition, consider the health of each tree before treating.  Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50% canopy thinning.  Insecticide treatments are not suggested for trees with greater than 50% canopy thinning.  Ash trees with greater than 50% canopy thinning should be removed and destroyed in accordance with established state and federal guidelines.  For additional information on this topic, see University of Wisconsin Garden Pest Alert XHT1215, Is My Ash Tree Worth Treating for Emerald Ash Borer.

Emerald ash borer insecticide treatment options.  Insecticide products that are available for use by professionals, with information on appropriate application methods and application timings, are summarized in Table 1.  These products include:

  • Ace-Jet (acephate)
  • ACECAP Systemic Insecticide Tree Implants (acephate)
  • ArborMectin (emamectin benzoate)
  • AzaGuard (azadirachtin)
  • Bifen XTS (bifenthrin)
  • Boxer Insecticide-Miticide (emamectin benzoate)
  • Dinocide, Dinocide HP (dinotefuran)
  • IMA-jet, IMA-jet 10 (imidacloprid)
  • Imicide, Imicide HP (imidacloprid)
  • Inject-A-Cide B (bidrin)
  • Mectinite (emamectin benzoate)
  • Merit 2F, Merit 75 WP, Merit 75 WSP (imidacloprid)
  • OnyxPro (bifenthrin)
  • Pointer (imidacloprid)
  • Safari (dinotefuran)
  • Tempo (cyfluthrin)
  • Transtect (dinotefuran)
  • Tree-äge, Tree-äge G4, Tree-äge R10 (emamectin benzoate)
  • Treeazin (azadirachtin)
  • TreeMec Inject (emamectin benzoate)
  • Xytect 2F, Xytect 75 WSP, Xytect 10% infusible (imidacloprid)
  • Zylam (dinotefuran)

University research indicates that soil drenches or injections of imidacloprid provide excellent EAB protection for small ash trees [less than six inches diameter at breast height (DBH)] in the first year following treatment.  Larger trees may require two consecutive years of treatment before they are effectively protected.  Thus, treatment of large trees should begin before the trees become infested.  While spring and/or fall applications are allowed on certain product labels, recent university research has indicated that spring applications have been more effective at controlling EAB and protecting canopy health.  Most insecticide treatments must be repeated each year.  Products containing emamectin benzoate are labeled to provide two years of protection.  Recent university research suggests that some of these products may provide more than three years of control with a single application when used at the highest labeled rate.

Trunk injections and implants require physically drilling or coring into a tree during the application of the insecticide.  Thus, use of these application methods has the potential to cause injury to trees (especially smaller trees), and may provide entry points for certain disease-causing fungi [e.g., Nectria, the cause of Nectria canker (see University of Wisconsin Garden Facts XHT1094 Nectria Canker)].

Table 1.  EAB insecticide treatments available to professionals*
Active Ingredient Product(s) Timing Application Method
Acephate ACE-Jet Mid-May to mid-June Trunk Injection
Acecap Implants Trunk Implant
Azadirachtin AzaGuard, Treeazin Early/mid-April to
early September
Trunk Injection
Bidrin Inject-A-Cide B Inject when infestation is evident Trunk injection
Bifenthrin Bifen XTS, OnyxPro Apply prior to or just at the time of adult emerge. Multiple applications may be needed Preventative bark and foliage cover sprays
Cyfluthrin Tempo
Dinotefuran Dinocide, Dinocide HP Late-April to late-May Trunk injection
Safari, Transtect, Zylam Soil drench, trunk spray
Emamectin benzoate ArborMectin, Boxer, Mectinite, Tree-äge, Tree-äge G4, Tree-äge R10, TreeMec April to September Trunk injection
Imidacloprid Merit 75 WP, Merit 75 WSP, Merit 2F, Xytect 2F, Xytect 75WSP, and others Mid-April to late-May


Early-Sept. to mid-October

Soil injection or drench
IMA-jet, IMA-jet 10, Imicide, Imicide HP, Pointer, Xytect 10% Mid-April to mid-May Trunk injection

The University of Wisconsin does not endorse any one specific commercially available insecticide.  Products discussed in this fact sheet have been evaluated in a variety of university research tests on EAB (  No matter which insecticide you use, always read and follow all label instructions.  Avoid skin contact with insecticides and safely store insecticides out of the reach of children.

For more information on controlling emerald ash borer:
See, or, University of Wisconsin Pest Alerts XHT1181 (Homeowner Guide to Emerald Ash Borer Insecticide Treatments) and XHT1215 (Is My Ash Tree Worth Treating for Emerald Ash Borer).

Cranberry Flea Beetle

The cranberry flea beetle (CFB) or redheaded flea beetle, Systena frontalis, is native to the United States ranging in the east from Maine to Florida and in the west from Texas to Montana.  CFB has historically been an important pest in nurseries, greenhouses and agricultural crops.  In the last decade, the insect has become an emerging, sporadic pest on cranberries.  CFB has likely always been present in cranberry marshes in Wisconsin but probably was not a problem in the past because of widespread use of broad-spectrum insecticides for control of other cranberry insect pests.  The relatively recent appearance of problems with CFB may be a consequence of growers using more selective insecticides for pest control.

A cranberry flea beetle adult (left) and larva (right). Note the fleshy projection at the rear end of the larva (white arrow). Photos courtesy of Shannon Schade (left) and Tim Dittl, UW-Madison (right).
A cranberry flea beetle adult (left) and larva (right). Note the fleshy projection at the rear end of the larva (white arrow). Photos courtesy of Shannon Schade (left) and Tim Dittl, UW-Madison (right).

Appearance:  Adult CFBs are shiny, black beetles with a reddish head.  They are approximately 1/10 to 1/4 inch long with antennae nearly half as long as their bodies.  They also have enlarged hind legs, which they use for jumping when disturbed.  Adult females are slightly larger than males.  Larvae are 1/5 to 1/4 inch long with a fleshy projection at the tip of their rear ends.

Host Range:  CFB has a very broad host range that includes many woody and herbaceous plants.  In cranberry production areas, the insect prefers to feed on weeds such as marsh St. John’s-wort, Joe-pye weed, smartweed, jewelweed, and hardhack spirea.  If these weedy species are not present or are kept mowed, CFB will move to cranberry beds and feed on cranberry foliage and fruits.  CFB is also an occasional pest of other commercial crops, including alfalfa, beans, beets, blueberries, cruciferous vegetables, eggplant, grapes, horseradish, potato and sweet potatoes.

Symptoms and Effects:  CFB larvae feed on cranberry roots and underground runners.  When CFB infestations are severe, larval feeding can lead to girdled roots and vine death.  Adult CFBs feed on foliage and on the surface of cranberry fruit.  Severe adult infestations can lead to skeletonization of leaves (i.e., loss of the tissue between veins) and death of upright vines.  Heavy feeding by adults can also impact bud development, leading to yield reductions the year following an infestation.  Because adults prefer areas of lush growth, adult CFB populations and damage are usually patchy.

Life Cycle:  In Wisconsin, female CFBs deposit single eggs into the soil in late summer through early fall, and the eggs serve as the overwintering stage of the insect.  In the spring, the eggs hatch, and CFB larvae feed on roots from June through August.  Larvae eventually pupate (this stage of the insect’s life cycle has not been formally described) and adults begin to emerge in July and are present through September.  In Wisconsin, CFB has one generation per year.

Scouting Suggestions:  Monitoring for CFB focuses on adult beetles, because finding larvae in the soil is difficult.  To evaluate CFB numbers, use a sweep net to capture adults.  Be sure to sample thoroughly across different areas within a cranberry bed to account for the patchy distribution of CFB adults.  There is no established action threshold for CFB in cranberry.  However, University of Maine Extension recommends taking action if you find more than 15 CFB per 25 sweeps in a cranberry bed.

Leaf damage with skeletonization (left) and root damage (right) due to cranberry flea beetle feeding. Photos courtesy of Tim Dittl, UW-Madison.
Leaf damage with skeletonization (left) and root damage (right) due to cranberry flea beetle feeding. Photos courtesy of Tim Dittl, UW-Madison.

Control:  Current management of CFB targets the adult stage.  If scouting indicates significant numbers of adult CFBs, consider using insecticide sprays for control.  Products that are effective against CFB adults include neonicotinoids (e.g., clothianidin, thiamethoxam, acetamiprid, dinotefuran), diamides (e.g., chlorantraniliprole, cyantraniliprole), spinosyns (e.g., spinetoram), organophosphates (e.g., chlorpyrifos, phosmet, diazinon) and carbamates (e.g., carbaryl).  When using insecticides, be sure to alternate use of at least two active ingredients in different IRAC chemical classes to help delay the development of insecticide resistance.  Also be sure to consider any adverse effects that the insecticides you use may have on non-target and beneficial insects.  Check University of Wisconsin Bulletin A3276 (Cranberry Pest Management in Wisconsin), available at, for additional insecticide recommendations.

DO NOT use soil insecticide applications in an attempt to target CFB larvae.  Such treatments are not effective.

Alternative management strategies for CFB have not been adequately researched.  Because CFBs prefer to feed on weed species, researchers speculate that use of trap crops may eventually become a useful management strategy.  In the area of biocontrol, current research at the University of Wisconsin-Madison indicates that native Wisconsin entomopathogenic nematodes significantly suppressed CFB larvae populations in soil.  At this time however, these nematodes are not available commercially.  In addition, work is needed to identify natural enemies of CFB that might be used to help manage the pest.

For more information on cranberry flea beetle:  Contact your county Extension agent.

Fungus Gnats on Houseplants

Fungus gnats (Family Sciaridae) are insects commonly associated with overwatered houseplants.  They can become a nuisance when they are present in large numbers and fly around inside a home.  In most situations, fungus gnats are a cosmetic problem.  However, on occasion, fungus gnat larvae can cause plant damage.

A fungus gnat adult. Note the Y-shaped wing veins (arrow). Photo courtesy of B. Schoenmakers (

Appearance:  Adult fungus gnats are delicate, dark brown or black flies that are approximately 1/8 inch long.  They have dark, translucent wings that fold on their backs when they are at rest.  Adult fungus gnats can be distinguished from other small flies by the vein patterns of their wings.  When viewed with a magnifying glass, fungus gnat wings have a distinct rounded Y-shaped set of veins near the wing tips.  Fungus gnat larvae (maggots) resemble pale worms and have a black head.  They are ¼ inch in length when mature.  Fungus gnats are often mistakenly identified as fruit flies (see University of Wisconsin Garden Facts XHT1102, Fruit Flies in the Home), but these are two distinct insects.

Symptoms and EffectsFungus gnats are usually noticed indoors when adults fly around light sources (e.g., windows, lamps), or when they fly around or walk across and rest on the soil of potted plants.  Adult fungus gnats do not feed on or damage plants but are a cosmetic nuisance.  Fungus gnat larvae typically feed on decaying organic matter and fungi in the soil.  However, if larval numbers are high, they may damage roots by feeding on root hairs or tunneling into the roots themselves.  This sort of damage is rare in home settings.

Life CycleFungus gnats can go through multiple generations per year.  Indoors, fungus gnats tend to have overlapping generations where eggs, larva, pupae and adults are all present at the same time.  Fungus gnat females lay up to 200 eggs (in clusters) in cracks and crevices on the surface of the moist soil of potted plants.  The eggs typically hatch within three to six days.  Larvae go through four stages (called instars) over the course of one to two weeks before they pupate near the surface of the soil.  Approximately four to five days after pupae form, adult fungus gnats emerge.  Adults are short-lived, surviving approximately one week.  Under optimal conditions, fungus gnats can develop from egg to adult in three to four weeks.

Scouting SuggestionsMonitor for fungus gnat adults using yellow sticky traps placed near a plant’s leaves.  You can buy these traps at your local hardware or garden store.  Sticky traps are inexpensive and often include small stakes making them easy to use with potted plants.  Sticky traps not only help capture adult fungus gnats (and other insect pests as well), but they can help you keep track of the number of fungus gnats (and other insects) over time.  Vinegar traps and other methods commonly used to monitor for fruit flies do not work for monitoring for fungus gnats.

To monitor for fungus gnat larvae, place potato slices on the soil surface of potted plants.  If there are fungus gnat larvae in the soil, they will come to the surface to feed on the potato tissue.  Check the slices for maggots after three to four days.


Use yellow sticky cards to trap fungus gnat adults.

Non-ChemicalAs noted above, using sticky traps can help control fungal gnats.  However, altering environmental conditions of houseplants is the single most important step in managing this insect.  Keep the soil surface dry to eliminate favorable egg-laying sites for the insect.  You can do this by allowing the top inch of the soil to dry out before you water.  Alternatively, you can water from the bottom to provide moisture for the roots while keeping the soil surface dry.  In addition, you can cover the soil with a ½ to one inch layer of coarse sand or fine gravel, which will help keep the surface drier and make the soil less attractive for egg-laying.

Fungus gnats are often more of a problem in the fall when houseplants that have been outdoors for the summer, and have become infested, are brought back indoors.  It may take three to four weeks of modified watering and use of sand/gravel to get fungus gnats in check.

BiologicalProducts containing Bacillus thuringiensis subsp. israelensis (Bti) are available to homeowners (e.g., Gnatrol, Mosquito Bits, etc.) and can be used to control fungus gnat larvae in soil.  These treatments do not affect eggs, pupae or adult fungus gnats.  Apply these products with adequate water to help the Bti filter through the soil to reach the larvae.  Use several applications spaced five to seven days apart to control newly hatched larvae until the infestation is under control.

ChemicalUnless a fungus gnat infestation is severe, chemical controls are not warranted.  If adult numbers are excessive however, insecticides containing pyrethrins or synthetic pyrethroids can provide temporary control.  If you decide to use insecticides, select a product that is labeled for indoor use on houseplants, and read and follow all product label instructions.  Apply insecticides to plants and to the surface of potting soil where adults typically rest.  DO NOT spray the air with these products as such treatments are ineffective.  Even in those situations where insecticide use may be warranted, keep in mind that chemical treatments should not be your sole management approach.  Insecticides should always be used in combination with other non-chemical practices (see above).

For more information on fungus gnats:  Contact your county Extension agent.

Black Stem Borer

Black stem borer (BSB), Xylosandrus germanus, also known as the alnus ambrosia beetle, is an invasive beetle from Asia (primarily Japan, Korea, Vietnam, China, and Taiwan) that was accidentally introduced into central Europe and North America.  BSB has traditionally been considered a serious pest of nursery and landscape trees, but has also been reported as a pest of fruit crops.  In the 1930’s, BSB was first detected in grapes in New York, and more recently, BSB has become increasingly active on fruit trees, particularly in New York and Michigan.

A black stem borer entry hole (left), a compressed sawdust toothpick emerging from an entry hole (right), and an adult black stem borer (inset). Photos courtesy of Deborah Breth (Cornell Cooperative Extension), Chris and Juli McGuire (Two Onion Farm), and Maja Jurc (University of Ljubljana), respectively.
A black stem borer entry hole (left), a compressed sawdust toothpick emerging from an entry hole (right), and an adult black stem borer (inset). Photos courtesy of Deborah Breth (Cornell Cooperative Extension), Chris and Juli McGuire (Two Onion Farm), and Maja Jurc (University of Ljubljana), respectively.

Since 2013, BSB has been detected in 21 counties in Wisconsin (Crawford, Dane, Grant, Iowa, Jefferson, Kenosha, La Crosse, Lafayette, Manitowoc, Milwaukee, Ozaukee, Portage, Racine, Richland, Rock, Sauk, Shawano, Sheboygan, Trempealeau, Vernon, and Waukesha).  Prior to 2019, BSB had only been found in Wisconsin at lumberyards and wood waste disposal sites.  However, in June 2019, BSB was confirmed in a commercial apple orchard in Lafayette County, WI.  The reason for the movement of BSB from ornamentals to fruit trees is unclear, but this movement raises concerns about damage that BSB may cause in commercial orchards in the future.

Appearance:  Adult BSBs are small insects that are between 1/8 and 1/16 inches in length.  They are reddish brown to nearly black in color and cylindrical.  Only females are known to fly.  Larvae are small, white, legless grubs.

Host Range:  BSB can attack over 200 species of ornamental trees including oak, elm, red maple, beech, hickory, chestnut, magnolia, pear, dogwood, black cherry, tupelo, and black walnut.  It can also attack fruit crops such as apple, apricot, cherry, grape, pear and plum.

Symptoms and Effects:  Wilting and dieback are typically the first noticeable symptoms of a BSB infestation.  These symptoms are the result of defense responses on the part of the tree to the presence of BSB.  General tree decline and eventual death often follow.  Small holes in the lower trunks of infested trees are another typical symptom of a BSB infestation.  Columns of compressed sawdust (called “toothpicks”) often emerge from these holes.  Dry, dark-colored, blistery bark and oozing sap are other typical symptoms.

BSB activity may occur in association with plant diseases such as fire blight (see University of Wisconsin Garden Facts XHT1090, Fire Blight) and other canker diseases (e.g., Fusarium canker).  It is unclear if stress from these diseases makes trees more attractive to BSB, if BSB is spreading disease-causing organisms, or both.

Life Cycle:  BSB overwinters as adults (primarily females) in host trees.  Overwintering adults are usually found in higher numbers in wooded areas, and they move to other nearby trees (including orchard trees) from these areas in the spring.  Overwintering adults become active in late April to early May following one to two consecutive days where temperatures are 68°F or higher.  After mating, females (the only adults known to fly) search for new hosts.  They can fly more than 330 feet to colonize new trees.  BSB prefers trees that are three inches or less in diameter.

Trees stressed from flooding, frost injury, and drought are particularly attractive to BSB.  Stressed trees produce several types of volatile chemicals (including ethanol) that attract BSB.

A black stem borer trap. Photos courtesy of Deborah Breth (Cornell Cooperative Extension).
A black stem borer trap. Photos courtesy of Deborah Breth (Cornell Cooperative Extension).

Once females locate suitable trees, they bore holes (approximately 1/16 inches in diameter) in the trunks, typically in the lower two to three feet.  Females create a network of tunnels (galleries) under the bark where they lay eggs and where their larvae develop.  Females lay one egg per day and can deposit up to 18 eggs.  After eggs hatch, larvae develop through three stages (instars) before maturing into adults.  This process takes approximately 30 days.  New adults typically emerge in July and a second round of mating, tunneling, egg-laying and larval development occurs.  The second generation of BSB adults (which overwinters) typically begins to appear around the end of August and into September.

Interestingly, BSB adults and larvae do not feed on plant tissue, but on a symbiotic fungus (Ambrosiella hartigii) that females carry in internal pouches (called mycangia).  Females disseminate the fungus in their galleries where it grows and spreads providing a food source for the beetles.

Scouting Suggestions:  Routinely examine trees for typical symptoms of BSB (as described above).  Also consider using ethanol-baited traps to monitor the flight activity of adult females in the spring.  Make traps from one- or two-liter plastic bottles, cutting two to four windows from the sides.  Cap the modified bottles and hang them upside down at a height of 20 inches.  Concentrate traps around sensitive trees (particularly orchard trees) near wooded areas.  Bait traps by adding one cup of vodka (which serves as the ethanol attractant and also the drowning solution) or by hanging a ready-made ethanol lure inside the trap and filling the bottom of the trap with a small amount of a drowning solution (e.g., soapy water or antifreeze).  DO NOT use rubbing alcohol in these traps.  Check traps at least weekly for drowned beetles.  Identification of BSB requires use of a microscope and proper training.  If you suspect BSB, send a specimen or good digital photo to the UW-Madison Insect Diagnostic Lab (

Control:  Remove and burn infested trees where 75% or more of the branches are dying.  Mow (with a flail mower) or burn large brush piles as these may harbor beetles that can cause new infestations.  Minimize stresses on trees (as described above) to make them less attractive to BSB.  Insecticide treatments may be useful for protecting trees in areas where BSB is a problem.  Young trees near woodlot edges are at greatest risk of injury and the most likely to benefit from insecticide applications.  However, application of insecticides should be considered carefully as these sprays can negatively impact pollinators.  If you decide to spray, treat trunks in the spring when BSB females emerge.  This occurs at around 75 growing degree days base 50°F (see University of Wisconsin Garden Facts XHT1086, Degree Day Calculation for details).  Follow with a second trunk spray as needed.  Use products containing pyrethroids (particularly permethrin).  These products can be used on apple trees where they will help control BSB, as well as green fruitworm and spotted tentiform leafminers, two other apple insect pests.  Note that because BSB does not feed on woody tissue but rather on the Ambrosiella fungus, systemic insecticides that control other borers will not be effective against BSB.

For more information on black stem borer:  Contact your county Extension agent.

Japanese Beetle

The Japanese beetle, Popillia japonica, is a significant pest of landscape trees and shrubs, vegetable and fruit crops, and turfgrass in the eastern United States.  The Japanese beetle is native to the Japanese archipelago and was first discovered in the U.S. in southern New Jersey in 1916.  The beetle does well in areas with moderate temperatures and precipitation.

Japanese beetle adults.
Japanese beetle adults.

Description:  Japanese beetle adults are a shiny, metallic-green and slightly less than ½ inch long.  They have coppery-brown wing covers (elytra) that rest on their backs.  At the edges of their backs are small patches of white hairs.  Males and females look similar, but females tend to be slightly larger.  Newly hatched larvae (white grubs) are C-shaped, approximately ⅛ inch long with pale bodies; mature grubs are up to one inch long.  Japanese beetle larvae are similar to those of other white grub species such as May/June beetles (see University of Wisconsin Garden Facts XHT1240, May/June Beetles), European chafers (see University of Wisconsin-Madison Extension bulletin A4141, European Chafer), and northern masked chafers (see University of Wisconsin-Madison Extension bulletin A4130, Northern Masked Chafer).

Plants Attacked and Damage:  Japanese beetle adults do not damage turf but feed on leaves and flowers of over 350 species of fruits, vegetables, ornamentals, field and forage crops, and weeds.  Norway and Japanese maple, birch, crabapple, purple-leaf plum, rose, mountain ash, linden, grapes, and basil are preferred hosts.  Adults feed on the upper surfaces of leaves of most plants, consuming soft tissues between the veins, and leaving a lace-like skeleton.  Often, they feed in the upper canopy first.  Trees with extensive damage turn brown and drop their leaves.

Japanese beetle grubs feed below ground on the roots of turf and ornamentals.  They reduce a plant’s ability to take up enough water and nutrients to withstand hot, dry weather.  Initial grub injury in turf leads to localized patches of pale, dying grass, resembling damage from drought stress.  As grubs develop and feed further, damaged areas rapidly enlarge and merge to a point where the turf is not well-anchored and can be rolled back like carpet.  Additional damage can occur when animals (e.g., skunks, raccoons, crows, etc.) dig into the turf to feed on the grubs.

Life Cycle:  Japanese beetles have only one generation per year.  Adults typically begin to emerge in late June or early July around 1000 growing degree days (see University of Wisconsin Garden Facts XHT1086, Degree Day Calculation), and can be found into September.  Adult beetles are most active on warm sunny afternoons.  After mating, females burrow two to four inches into the soil in areas with higher soil moisture (e.g., under turf and in mulched areas) to lay small batches of eggs.  Eggs hatch after approximately two weeks, and grubs begin feeding on the roots of turfgrass and ornamentals.  By fall, grubs are nearly full-grown (approximately one inch long).  As soil temperatures begin to drop, grubs move deeper into the soil, typically overwintering six to eight inches (but up to 20 inches) below the surface.  They become inactive when soil temperatures fall below 50°F.  In the spring, when soil temperatures reach 50°F, the grubs move upwards to the root-zone to resume feeding for several weeks.  The grubs eventually stop feeding and create a cavity in the soil where they pupate (i.e., transform) into adults.


Landscape and Garden Plants:  Well-established trees and shrubs generally tolerate Japanese beetle damage with little impact on leaf emergence the following season.  However, regular, severe defoliation can make some plants more susceptible to other problems.  Birch and linden trees that suffer from repeated severe foliage damage can attract borers that can kill the trees.  To minimize the stress from defoliation, make sure trees are watered and mulched properly.  Also, consider consulting with a certified arborist (see about other management options for large trees.

Consider protecting smaller plants (e.g., vegetables, herbs, small shrubs and trees) from Japanese beetles by covering them with nylon insect screens from late June to early September.  Use a mesh size of ¼ inch or less and be sure to secure the edge of the mesh the ground.  On smaller plants, you can hand pick or knock off beetles and put them into a container of soapy water.

A Japanese beetle grub.
A Japanese beetle grub.

There are many insecticides that can protect foliage and flowers from Japanese beetle adults.  When selecting an insecticide, consider the potential impact of the product on non-target organisms (e.g., bees and other pollinators, pets and humans).  Chlorantraniliprole (the active ingredient in Acelepryn) is a reduced risk insecticide that has minimal impact on non-target organisms, but provides effective Japanese beetle control for 28 days.  This product can be used on trees, shrubs and herbaceous perennials.  Bacillus thuringiensis subsp. galleriae or Btg (the active ingredient in beetleGONE!) is also a reduced risk insecticide.  It can be used on a wide range of landscape plants, vegetable and fruit crops and is approved for organic production.  Other organic insecticides like azadirachtin and pyrethrins (both found in numerous products) also provide reduced environmental impact and can be used on landscape plants, vegetables and berry crops.  However, these products should be applied in late evening after pollinator activity subsides.  The most commonly available products for Japanese beetle adult control contain synthetic compounds in the pyrethroid class of insecticides (e.g., bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin, permethrin, zeta-cypermethrin, etc.).  These insecticides typically protect foliage for approximately two weeks.  The downside to these insecticides is that they can also kill beneficial insects (e.g., pollinators or predators).  Whatever product you decide to use, follow all label instructions to ensure that you use the product in the safest and most effective manner possible.

Pheromone lure traps are not recommended for Japanese beetle control.  These traps capture large numbers of Japanese beetles, but also attract many more adults to the area that are not trapped and that can cause additional damage.

Finally, when landscaping, choose plants that are less favored by Japanese beetles.  Arborvitae, black gum, boxwood, clematis, dogwoods, firs, forsythia, fringetree, hemlock, hickory, holly, ironwood, junipers, lilac, magnolia, musclewood, northern red oak, pines, red maple, silver linden, spruces, sweet gum, tulip tree, white oak, yellowwood and yews tend to suffer less feeding damage from Japanese beetles.

Turf:  DO NOT water turf from July to mid-August when Japanese beetles are most active.  Drier conditions may discourage females from laying eggs and may also kill newly-laid eggs and young larvae.  If you decide to use insecticides for control, consult University of Wisconsin Garden Facts XHT1018 (White Grub Control in Turfgrass) for information on products that you can use and proper timings of applications.  Many grub control products can pose risks to bees and other pollinators.  Consult University of Wisconsin Extension Publication A4128 (Conservation of Native and Domestic Pollinators in Managed Turfgrass Landscapes) for guidance on protecting pollinators in turfgrass areas.  Note that controlling grubs in a lawn will not prevent damage from adult Japanese beetles in the future, as adults can fly in from nearby areas.

For more information on Japanese beetle:  See University of Wisconsin Garden Facts XHT1018 (available at, UW-Extension bulletins A3714 and A4128 (available at, or contact your county Extension agent.