Category Archives: Fact Sheet

Home Fruit Insecticides

Managing fruit crop insect pests can be very challenging.  Pest control involving multiple approaches (referred to as “integrated pest management”) is generally the most effective and safest strategy.  Before taking any management action, make sure to correctly identify any insect pest.  You can do this by submitting photos or samples of insects to your local county Extension office (see https://counties.extension.wisc.edu/ for details) or to the UW Insect Diagnostic Lab (see http://labs.russell.wisc.edu/insectlab/ for details).  Once your pest is identified, there are many resources available to determine the best method of control, which may or may not include use of insecticides.  If insecticides are needed, this fact sheet provides information on active ingredients in some common products that are labeled for use by home gardeners.  Additional information and alternative control measures for a variety of insect pests are available in Extension bulletins available at https://learningstore.extension.wisc.edu/ and University of Wisconsin Garden Facts fact sheets available at https://pddc.wisc.edu/.  Any products listed are intended as a guide; you as the user are responsible for following all label instructions.  Control recommendations for common fruit tree pest, such as aphids, leafrollers, and plum curculio are listed under apple only.  Make sure to not apply insecticides during bloom to protect pollinators.

Apples/Pears

Aphids

  • Acetamiprid
  • Azadirachtin
  • Carbaryl
  • Insecticidal Soap
  • Neem Oil
  • Permethrin
  • Pyrethrins
  • Zeta-Cypermethrin

Apple Maggot

  • Acetamiprid
  • Carbaryl
  • Kaolin clay
  • Pyrethrins
  • Zeta-Cypermethrin

Codling Moth

  • Acetamiprid
  • Bacillus thuringiensis kurstaki
  • Carbaryl
  • Permethrin
  • Pyrethrins
  • Spinosad
  • Zeta-Cypermethrin

Leafrollers

  • Acetamiprid
  • Azadirachtin
  • Bacillus thuringiensis kurstaki
  • Carbaryl
  • Permethrin
  • Pyrethrins
  • Spinosad
  • Zeta-Cypermethrin

Mites (Includes Pear Rust Mite)

  • Azadirachtin
  • Dormant Oil
  • Insecticidal Soaps
  • Neem Oil

Plum Curculio

  • Acetamiprid
  • Carbaryl
  • Kaolin Clay
  • Malathion
  • Permethrin
  • Pyrethrins
  • Spinosad
  • Zeta-Cypermethrin

Stink Bugs

  • Acetamiprid
  • Carbaryl
  • Permethrin

Scales

  • Acetamiprid
  • Azadirachtin
  • Dormant Oil
  • Insecticidal soap
  • Neem oil
  • Zeta-Cypermethrin

Stone Fruits (Apricots/Cherries/Peaches/Plums)

Cherry Fruit Fly

  • Carbaryl
  • Zeta-Cypermethrin

Cherry Fruitworm

  • Carbaryl
  • Spinosad
  • Zeta-Cypermethrin

Peachtree & Lesser Peachtree Borers

  • Permethrin

Spotted Wing Drosophila

  • Carbaryl
  • Spinosad
  • Pyrethrins
  • Zeta-Cypermethrin

Tarnished Plant Bug and Stink Bug

  • Azadirachtin
  • Carbaryl
  • Permethrin
  • Zeta-Cypermethrin

Brambles (Blackberries/Raspberries)

Aphids

  • Azadirachtin
  • Carbaryl
  • Insecticidal Soap
  • Malathion
  • Neem Oil
  • Zeta-Cypermethrin

Cane Borer

  • Prune out and destroy
    infested canes

Fruitworm

  • Carbaryl
  • Spinosad

Japanese Beetle

  • Azadirachtin
  • Bacillus thuringiensis galleriae
  • Carbaryl
  • Kaolin clay
  • Neem oil
  • Zeta-Cypermethrin

Leafrollers

  • Azadirachtin
  • Carbaryl
  • Spinosad
  • Zeta-Cypermethrin

Picnic Beetles

  • Carbaryl
  • Malathion
  • Bait traps with overripe fruit

Sawfly

  • Carbaryl
  • Insecticidal Soap
  • Malathion
  • Spinosad
  • Zeta-Cypermethrin

Spotted Wing Drosophila

  • Carbaryl
  • Spinosad
  • Pyrethrins
  • Zeta-Cypermethrin

Strawberries

Aphids

  • Azadirachtin
  • Carbaryl
  • Insecticidal Soap
  • Malathion
  • Neem Oil
  • Pyrethrins

Mites

  • Azadirachtin
  • Insecticidal Soap
  • Malathion
  • Neem Oil

Leafhoppers

  • Azadirachtin
  • Carbaryl
  • Malathion
  • Neem Oil

Plant Bugs

  • Azadirachtin
  • Carbaryl
  • Insecticidal Soap
  • Malathion

Slugs

  • Iron Phosphate
  • Metaldehyde bait

Spittlebugs

  • Carbaryl
  • Malathion

Strawberry Bud Weevil

  • Azadirachtin
  • Carbaryl
  • Malathion
  • Pyrethrins

Strawberry Leafroller

  • Acetamiprid
  • Azadirachtin
  • Bacillus thuringiensis kurstaki
  • Carbaryl
  • Spinosad

Grapes

Grape Flea Beetle

  • Carbaryl
  • Zeta-Cypermethrin

Grape Phylloxera

  • Acetamiprid

Japanese Beetle

  • Azadirachtin
  • Bacillus thuringiensis galleriae
  • Carbaryl
  • Kaolin clay
  • Neem Oil
  • Zeta-Cypermethrin

Multicolored Asian Lady Beetle

  • Carbaryl

Wasps

  • Remove nests, place traps

For more general fruit information and more information on insecticides that can be used on other types of plants:  See https://fruit.wisc.edu/ and University of Wisconsin Garden Facts XHT1095 (Home Turf Insecticides), XHT1096 (Home Landscape Insecticides), and XHT1097 (Home Vegetable Insecticides) available at https://pddc.wisc.edu/, or contact your county Extension agent.

Typhula Blight

Typhula blight causes circular patches of bleached turf that often merge to form larger, irregularly-shaped bleached areas.
Typhula blight causes circular patches of bleached turf that often merge to form larger, irregularly-shaped bleached areas.

What is Typhula blight?  Typhula blight, also known as gray or speckled snow mold, is a fungal disease affecting all cool season turf grasses (e.g., Kentucky bluegrass, creeping bentgrass, tall fescue, fine fescue, perennial ryegrass) grown in areas with prolonged snow cover.  These grasses are widely used in residential lawns and golf courses in Wisconsin and elsewhere in the Midwest.

What does Typhula blight look like?  Typhula blight initially appears as roughly circular patches of bleached or straw-colored turf that can be up to two to three feet in diameter.  When the disease is severe, patches can merge to form larger, irregularly-shaped bleached areas.  Affected turf is often matted and can have a water-soaked appearance.  At the edges of patches, masses of grayish-white fungal threads (called a mycelium) may form.  In addition, tiny (1/64 to 3/16 inch diameter) reddish-brown or black fungal survival structures (called sclerotia) may be present.  Typhula blight looks very similar to Microdochium patch/pink snow mold (see University of Wisconsin Garden Facts XHT1145, Microdochium Patch), but the Microdochium patch fungus does not produce sclerotia.   

Where does Typhula blight come from?  Typhula blight is caused by two closely related fungi Typhula incarnata and Typhula ishikariensis.  In general, T. incarnata is more common in the southern half of Wisconsin while T. ishikariensis is more common in the northern half of the state.  To distinguish between the two Typhula species, look for sclerotia.  Sclerotia of T. incarnata are reddish-brown and 1/16 to 3/16 inches in diameter.  Sclerotia of T. ishikariensis are black and 1/64 to 1/16 inches in diameter, resembling flakes of pepper.  Typhula blight develops when there is a prolonged period (more than 60 days) when snow covers unfrozen ground and soil temperatures are just above freezing (30 to 40˚F).  Typhula blight typically does not develop if the ground freezes before the first snowfall in the fall/winter, or if snow melts during the middle of winter exposing the ground to colder temperatures.  Damage from Typhula blight is usually not noticed until snow melts in spring.  Applying high nitrogen fertilizers in the fall can increase the risk of Typhula blight developing over the winter.

Sclerotia (survival structures) of Typhula incarnata are small and red or rust-colored.
Sclerotia (survival structures) of Typhula incarnata are small and red or rust-colored.

How do I save a turf with Typhula blight?  Turf with Typhula blight may or may not recover depending on the fungus involved.  Both T. incarnata and T. ishikariensis can infect and kill turf leaves, but only T. ishikariensis kills the plant crown.  Turf infected with T. incarnata typically recovers quickly once normal turf growth resumes in the spring.  Turf infected by T. ishikariensis often suffers from crown injury and death making it less likely to recover and more likely to require replanting in spring.  Lightly raking infected turf and reseeding in spring can help speed turf recovery.

How do I avoid problems with Typhula blight in the future?  Consider planting less-susceptible turfgrass species (e.g., fine fescues) to limit the impact of Typhula blight.  Also, avoid using fast-release fertilizers in late fall that can predispose turf to Typhula infections.  Finally, continue to mow turf until it goes dormant as this will help prevent excessive turf top growth that is more easily infected by Typhula.

Because turf often recovers naturally from Typhula blight, fungicide treatments are typically NOT warranted for home lawns.  However, fungicide treatments may be needed to prevent severe damage when a lawn has a history of the disease and when predictions for the upcoming winter suggest that snow cover will persist on unfrozen ground for longer then three months.  Many effective fungicides are available for snow mold control in home lawns and include the active ingredients azoxystrobin, propiconazole, pyraclostrobin, and tebuconazole.  For the most up-to-date fungicide recommendations for Typhula blight, please visit the Turf Pest Management Mobile website (https://turfpests.wisc.edu/).  Fungicide applications should be made in October or November to prevent disease in the spring.  If you decide to use fungicides for control, read and follow all label instructions to ensure that you use the product that you select in the safest and most effective manner possible.

For more information on Typhula blight:  Contact the Turfgrass Diagnostic Lab (https://tdl.wisc.edu/) or your county Extension agent.

Sudden Oak Death

What is sudden oak death?  Sudden oak death (also called Ramorum leaf blight or Ramorum dieback) is an oftentimes lethal disease that has caused widespread death of tanoak (Lithocarpus densiflorus), coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), and Shreve oak (Quercus parvula var. shrevei) in California.

Rapid wilting and die back of branch tips can be a symptom of ramorum dieback.
Rapid wilting and die back of branch tips can be a symptom of ramorum dieback.

The disease can affect or has been reported in association with a wide range of woody and herbaceous plants including, but not limited to bigleaf maple (Acer macrophyllum), Bodnant viburnum (Viburnum X bodnantense), ‘Brouwer’s Beauty’ pieris (Pieris floribunda X japonica), California bay laurel (Umbellularia californica), California buckeye (Aesculus californica), California coffeeberry (Rhamnus californica), California honeysuckle (Lonicera hispidula), canyon live oak (Quercus chrysolepis), coast redwood (Sequoia sempervirens), doublefile viburnum (Viburnum plicatum var. tomentosum), douglas-fir (Pseudotsuga menziesii var. menziesii), evergreen huckleberry (Vaccinium ovatum), Formosa firethorn (Pyracantha koidsumii), ‘Forest Flame’ pieris (Pieris formosa X japonica), Himalaya pieris (Pieris formosa), Japanese camellia (Camellia japonica), Japanese pieris (Pieris japonica), laurustinus (Viburnum tinus), madrone (Arbutus menziesii), manzanita (Arctostaphylos manzanita), rhododendron (Rhododendron spp.), Sasanqua camellia (Camellia sasanqua), toyon (Heteromeles arbutifolia), western starflower (Trientalis latifolia), and witch hazel (Hamamelis virginiana), Burkwood viburnum (Viburnum X burkwoodii), California hazelnut (Corylus cornuta), Camellia X williamsii, cascara (Rhamnus purshiana), Chinese pieris (Pieris formosa var. forrestii), common lilac (Syringa vulgaris), David viburnum (Viburnum davidii), drooping leucothoe (Leucothoe fontanesiana), European beech (Fagus sylvatica), European cranberrybush viburnum (Viburnum opulus), European turkey oak (Quercus cerris), European yew (Taxus baccata), fragrant viburnum (Viburnum farreri), grand fir (Abies grandis), Holm oak (Quercus ilex), horse-chestnut (Aesculus hippocastanum), lingonberry (Vaccinium vitis-ideae), mountain laurel (Kalmia latifolia), Northern red oak (Quercus rubra), Pieris formosa var. forrestii X Pieris japonica, poison oak (Toxicodendron diversiloba), Prague viburnum (Viburnum X pragense), reticulate camellia (Camellia reticulata), salmonberry (Rubus spectabilis), Southern red oak (Quercus falcata), strawberry tree (Arbutus unedo), sweet chestnut (Castanea sativa), Viburnum X carlcephalum X Viburnum utile, Victorian box (Pittosporum undulatum), wayfaringtree viburnum (Viburnum lantana), and wood rose (Rosa gymnocarpa).

Sudden oak death was first reported in the US in California and has subsequently been found in other US states, including in Wisconsin in 2019.  Sudden oak death has also been reported in Europe.

What does sudden oak death look like?  Symptoms of sudden oak death vary depending upon the plant species infected.  On some hosts, infections occur primarily on leaves leading to light brown leaf spots and blotches.  These leaf symptoms may be indistinguishable from other, more common, leaf spots and blights, or may mimic sunburn or leaf scorch symptoms.  Twigs and branches that become infected often wilt, forming a “shepherd’s-crook”, and subsequently die back.  Infection of tree trunks leads to cankers (i.e., sore-like areas) that produce large amounts of an amber to black colored ooze.  This ooze can dry to form a stained area on the bark.  Removing the bark over the affected area will reveal discolored wood beneath that sometimes (but not always) has a black border.  Cankers can eventually expand to girdle trunks, thus resulting in the death of the tree or shrub.  Trunk infections appear not to extend into the root system of the plant.  Once sudden oak death cankers develop, other pathogens may invade the infected areas, accelerating tree or shrub death and complicating the diagnosis of the disease.

Where does sudden oak death come from?  Sudden oak death is caused by the fungus-like water mold Phytophthora ramorum, which was first recognized as a pathogen in 1995.  Phytophthora ramorum can be spread over long distances through movement of infected plants or infested plant parts.  The organism can also be moved with contaminated soil (e.g., on vehicle tires, tools, or shoes), or in contaminated water.  Once established on plants in a given location, the fungus produces reproductive structures (called sporangia) that can be moved from plant to plant by rain splash, or wind.  Phytophthora ramorum was introducing into Wisconsin in 2019 on nursery stock grown in the state of Washington.

Ramorum leaf blight symptoms can mimic those of other leaf spots and blights.
Ramorum leaf blight symptoms can mimic those of other leaf spots and blights.

How do I save a plant with sudden oak death?  If you believe you have seen a plant that has sudden oak death, please IMMEDIATELY submit a sample to the Plant Disease Diagnostics Clinic (PDDC), care of the address in the box at the bottom of this page.  Double bag suspect plant tissue in sealable plastic bags and place the bagged specimen in a box or envelope for shipping.  Include contact information (complete address, phone number, email address) in a separate sealable plastic bag with the sample.  Tape over all of the edges of boxes and envelopes used for shipping to keep everything sealed inside.  Write on the box or envelope that the box or envelope contains a suspect SOD sample.  If you have questions about collecting or submitting a sample, contact PDDC staff at (608) 262-2863 or at pddc@wisc.edu.

Because Phytophthora ramorum is a regulated, quarantined pathogen, DO NOT remove the affected plant (or parts thereof) or take the plant from the site where it is located, other than to collect a specimen for submission for a diagnosis.  Be sure to decontaminate any tools or other items that come into contact with the plant (including those used to collect a diagnostic sample) by dipping them for at least 30 seconds in 10% bleach.  If a plant tests positive for Phytophthora ramorum, it will be removed and destroyed to help prevent further spread of the pathogen.

How do I avoid problems with sudden oak death in the future?  Carefully inspect any new nursery stock upon delivery (or prior to purchase, if possible) for symptoms of sudden oak death.  Keep new stock isolated from older stock as long as possible, to minimize possible movement of the pathogen should the disease develop after plants have arrived.  If you see any suspect symptoms, alert the PDDC so that arrangements can be made for proper testing for Phytophthora ramorum.

For more information or help in diagnosing sudden oak death:  Contact Brian Hudelson, UW-Madison Plant Disease Diagnostic Clinic, Department of Plant Pathology, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI  53706-1598, phone: (608) 262-2863, email: pddc@wisc.edu, see the USDA APHIS sudden oak death website https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/phytophthora-ramorum/sod, or contact your County Extension agent.

Cabbage Maggot

The cabbage maggot (Delia radicum) is an early season pest of cruciferous/cole crops (e.g., cabbage, broccoli, Brussels sprouts, cauliflower, kohlrabi, rutabaga, turnip, and radish), as well as cruciferous weeds (e.g., wild mustard, water cress, wild radish).  Cabbage maggot damages plants by feeding on their roots and lower stems.  Early season transplants and spring root crops are damaged most severely.  Wounds produced by cabbage maggot feeding not only cause damage directly to plants, but can also provide entry points for a number of disease-causing organisms that can cause additional damage.

Cabbage maggot larvae on cabbage roots.
Cabbage maggot larvae on cabbage roots.

Appearance: The adult cabbage maggot is an ash gray, bristly fly that resembles a housefly, but is half as long and has black stripes on its thorax.  Cabbage maggot larvae are 1/3 inch long (when mature), white and legless with bodies that taper toward their heads.  These larvae look similar to seed corn maggots, but differ in terms of their feeding choices.  Cabbage maggots prefer to feed on cruciferous plants, while seed corn maggots prefer to feed on seeds and seedlings of corn and cucurbits (e.g., cucumber, squash, pumpkin, watermelon).

Symptoms and Effects: Cabbage maggots feed both within and on the surface of roots.  Their feeding wounds provide entry points for the organisms that cause diseases such as black leg and bacterial soft rot [see University of Wisconsin Garden Facts XHT1224, (Bacterial Soft Rot) available at https://pddc.wisc.edu/fact-sheet-listing-all/ for details].  Maggots can be especially damaging to seedlings, injuring the growing points of the roots and stunting plant growth.  Injury to crops is more prevalent during wet, cool weather, which cabbage maggot prefers.  Injured plants become off-color and may eventually wilt as daytime temperatures increase in late spring.

Life Cycle: Cabbage maggots overwinter as pupae in the upper few inches of the soil.  Adults emerge in mid-May, about the same time that yellow rocket and forsythia are in bloom.  Adults are attracted to freshly-tilled fields with decaying organic matter where they lay eggs on the soil near the base of cole crops and other cruciferous hosts.  Eggs hatch in two to seven days and larvae immediately begin feeding on the roots of nearby host plants.  Feeding continues for three to four weeks before larvae pupate in the soil.  A second generation of adults emerges in late June and lays eggs which hatch producing additional larvae that feed and eventually pupate.  Typically, this second set of pupae survives the winter.  However, if warm weather extends the growing season, a third generation of cabbage maggot is possible and this third set of pupae survives the winter.

Scouting Suggestions:  You can predict adult cabbage maggot emergence using a 43°F base temperature degree day model where calculations begin once the ground has thawed.  First generation adults appear after 300 degree days have accumulated.  Second and third generation adults appear after 1476 and 2652 degree days respectively have accumulated.  For details on calculating degree days, see University of Wisconsin Garden Facts XHT1086 (Degree Day Calculation), available at https://pddc.wisc.edu/fact-sheet-listing-all/.

Alternatively, you can monitor for adult populations using yellow plastic bowls filled with soapy water.  In larger plantings, place bowls every 100 ft. along field edges.  Count flies every four to six days to determine if adult populations are increasing or decreasing.

Control

Cultural:  Effective cabbage maggot control is primarily preventative.  To avoid damage from this pest, till in any cover crops in fields to be planted to cole crops two to three weeks before seeding or transplanting.  Also, DO NOT plant cole crops in fields where animal manure has been freshly applied.  Be sure that soil temperatures are greater than 50°F at planting to promote quick emergence.  Time planting to avoid peak cabbage maggot adult emergence.  Plantings established after mid-June generally suffer less damage than plantings established earlier.  Optimally, transplants should be planted one to two weeks before peak adult emergence.

Floating row covers can be effective in protecting plants during cabbage maggot flight periods.  Diatomaceous earth, parasitic nematodes, and predaceous ground beetles may also help reduce cabbage maggot populations.  Immediately after harvesting a cole crop, work crop residues into the soil to reduce sites where the cabbage maggot can overwinter.

Chemical: In areas where cabbage maggot has historically been a problem, consider using insecticides applied at planting as either a drench or band application.  Apply this insecticide directly at the base of plants to avoid disrupting beneficial, soil-inhabiting insects.  See University of Madison Division of Extension bulletin A3422 (Commercial Vegetable Production in Wisconsin), available at https://learningstore.uwex.edu/, for detailed insecticide recommendations.  Note that there are no insecticide options for treating cabbage maggot once an outbreak has started.

For more information on cabbage maggot: See UW-Extension Bulletin A3422, or contact your county Extension agent.

Bagging Apples for Insect and Disease Control

Producing high quality apples in home gardens can be challenging due to damage caused by insects (e.g., apple maggot, codling moth, plum curculio, stinkbugs) and fungal diseases (e.g., apple scab, cedar-apple rust, flyspeck, sooty blotch).  Many insects damage apples when they lay their eggs in developing fruit.  Insect larvae can cause

Bagging apples can reduce fruit damage due to insects and diseases. (Photo courtesy of Janet van Zoeren)
Bagging apples can reduce fruit damage due to insects and diseases. (Photo courtesy of Janet van Zoeren)

additional damage as they tunnel into the fruit.  Wind-borne fungal spores can land on fruit leading to infections that damage fruit, reduce fruit aesthetics or affect long-term storage.

Although insecticide and fungicide sprays can help control insect pests and diseases, regular spraying can be inconvenient and costly for homeowners.  A non-pesticide alternative for protecting fruit is to encase apples in bags that provide protective barriers against insects and fungal pathogens.

What do I need to bag my apples?  First, you will need some sort of bagging material.  This could be a household plastic or paper bag, or a commercially-produced bag designed specifically for apple bagging.  Perhaps the most convenient choice is a common plastic sandwich or quart-size zip-type bag.  Zip-type bags are effective, weather proof, economical, and readily available.  You will also need something (e.g., a twist tie, tape, string, staples) to secure the bags to your apples and a pair of scissors to cut a drainage hole in each bag.

When do I bag my apples?  Start bagging when fruits are approximately ½ to 3/4 inch in diameter.  Apples typically reach this size approximately two weeks after petal fall.  Thin each cluster of apples to a single fruit, keeping the largest, best-shaped fruit in the cluster.  Make sure that the apples you select have not already been damaged.  In particular, plum curculio can damage fruit and codling moth can lay eggs before fruit are large enough to bag.  You may want to consider using an insecticide spray between petal fall and bagging to prevent this early damage.

How do I bag my apples?  Place an apple in the bag of your choice with the top of the bag around the stem.  Carefully secure the bag with a twist tie, tape, string or staple without damaging the stem.  If using a zip-type bag, place the stem in the middle and close the seal to within one inch of the stem on each side.  Staple the bag on each side of the stem to ensure that the bag will remain secure all summer.

Use scissors to cut approximately one-half inch from one of the bottom corners of the bag. This will allow condensation that may form inside the bag to drain.

Leave plastic bags on all summer.  Paper bags may deteriorate and need replacement if there is excessive rain during the growing season.  In addition, paper bags should be removed a few weeks prior to harvest to allow proper fruit color to develop.

Bagging apples can help prevent damage due to insect pests such as codling moth (left) and diseases such as apple scab (right). (Photos courtesy of Christelle Guédot and the UW-Plant Disease Diagnostics Clinic).
Bagging apples can help prevent damage due to insect pests such as codling moth (left) and diseases such as apple scab (right). (Photos courtesy of Christelle Guédot and the UW-Plant Disease Diagnostics Clinic).

What should my apples look like after they have been bagged?  Because bags prevent insects and fungal spores from reaching fruit, most of your bagged apples should be in near perfect condition.  Fruit that you do not bag will likely be blemished from insects and disease.  Blemished fruits should be removed (whether they fall to the ground or remain attached to your tree) and destroyed by burning (where allowed), deep burying or hot composting.  Diseased leaves from your apple tree should be treated similarly once they fall from the tree in the autumn.  Properly disposing of blemished fruits and diseased leaves will help limit overwintering of insect pests and disease-causing organisms, thus reducing insect and disease problems the following growing season.

For more information on bagging apples for insect and disease control:  Contact your county Extension agent.

African Fig Fly

The African fig fly (AFF), Zaprionus indianus, is an invasive vinegar fly closely related to flies in the genus Drosophila [which includes the common vinegar fly (also sometimes called the common fruit fly) and spotted-wing drosophila (SWD)].  AFF is native to Africa, Eurasia and the Middle East.  It was first detected in the United States in Florida in 2005, where it is now well established.  In 2012, AFF (a single adult) was first detected in Wisconsin.  In 2017, larger numbers of AFF were found in the state in traps used to monitor for SWD.

An African fig fly adult. (Photo courtesy of Benjamin Davidson)
An African fig fly adult. (Photo courtesy of Benjamin Davidson)

Outside of Wisconsin, AFF has had its biggest economic impact in commercial fig production, and has not been found to have a significant economic impact on other agricultural crops.  In Wisconsin, the potential economic impact of AFF on fruit and other crops is not yet known.  Because AFF reproduces readily and can rapidly expand its range, careful monitoring for this insect in the state is warranted.

Appearance:  The adult AFF is slightly larger than the common vinegar fly or SWD, and has a light-colored body and bright red eyes.  An adult AFF has four black-bordered, white stripes that run along each side of its head and thorax (but not its abdomen).  These stripes can easily be seen using a hand lens and are not found on any other vinegar flies in Wisconsin.  An AFF larva (maggot) is legless and has a single hook-like tooth at its mouth-end.  The maggot uses this tooth to feed on rotted berries and other soft fruit tissues.  AFF maggots are nearly indistinguishable from maggots of common vinegar flies and SWD.

Host Range:  AFF can feed on a large number of fruit crops grown in Wisconsin, including blackberries, blueberries, grapes, peaches, raspberries and strawberries, with grape being a preferred host.

Symptoms and Effects:  Given that AFF is a newcomer to Wisconsin and its temperate climate, predicting which fruits the insect will affect, and to what extent, is difficult.  What is known about AFF is that it cannot initiate damage to intact, ripe fruit; it can only feed on and lay eggs inside of overripe or already damaged fruit.  The insect contributes to additional breakdown and decay of these fruit.  In Wisconsin, AFF and SWD (which can damage intact, ripe fruit) will likely occur together at a given location, and will likely interact.  AFF may end up laying eggs in fruit damaged by SWD, possibly leading to an increase in AFF populations.  The effects of AFF on SWD populations are not clear at this time.  However, some research conducted in grapes suggests that where AFF and SWD occur together, they may compete, leading to increased numbers of AFF and lower numbers of SWD.

Life Cycle:  As an insect native to the tropics, AFF will likely not be able to survive even a mild winter in Wisconsin; in fact, AFF does not appear to overwinter even as far north as Virginia.  However, AFF can travel long distances on air currents, and could potentially travel from the southern US to Wisconsin in the spring and summer, leading to fruit infestations in the state in the summer and fall.  AFF has only been detected in Wisconsin in 2012 and 2017, suggesting that if the insect does cause problems in Wisconsin, these problems will not likely be a yearly occurrence.

Exactly how many generations of AFF might develop in Wisconsin in a given year is not known.  In the laboratory (at 75°F), AFF develops from egg to adult in 20 days and females lay, on average, 60 eggs.  Based on its short generation time and ability to produce numerous eggs, AFF populations could potentially build quickly within a given year, once the insect arrives in Wisconsin.

Monitoring:  Monitor for AFF using the same traps that you would use to monitor for SWD.  You can buy commercially available traps, or alternatively, you can make simple, inexpensive traps using a 32-ounce clear plastic container with a lid.  To allow adult flies to enter the trap, drill or melt ten 3/16 inch diameter holes around the top of the container.  Bait traps with one tablespoon active dry yeast and four tablespoons sugar in twelve ounces of water.  Alternatively, use a two-inch layer of apple cider vinegar in the bottom of the container.

Add one to two drops of unscented dish soap to the trap to break the surface tension of the liquid so that flies are more likely to

A homemade vinegar fly trap made from a 32-ounce clear plastic container with a lid. (Photo courtesy of Emma Pelton)
A homemade vinegar fly trap made from a 32-ounce clear plastic container with a lid. (Photo courtesy of Emma Pelton)

drown.  Hang traps in a shaded plant canopy where fruit is present.  For strawberries, place traps on the ground.  Check traps and replace liquid bait weekly, using a hand lens to identify trapped insects.  Be careful not to pour bait on the ground near the traps as this will confuse flies and reduce the effectiveness of the traps.  DO NOT bother testing fruit directly to determine infestation rates for AFF, as AFF larvae will be indistinguishable from those of other vinegar flies (e.g., common vinegar fly and SWD).

Control:  Because AFF cannot cause damage to sound fruit, and because recorded populations of AFF in Wisconsin have been low, AFF control may not be needed unless/until severe outbreaks occur.  Control methods recommended for SWD will likely also help control AFF.  In particular, cultural practices such as removing all damaged or rotting fruit and then solarizing (heating) or freezing this material to kill fly larvae may slow buildup of AFF at a given location in a given growing season.  However, because AFF is able to move over long distances from areas in the south where it can easily overwinter, reintroduction of the insect will be possible even if you follow strict sanitation practices.

Exclusion netting, which has been used with some success to manage SWD, will likely also help manage AFF.  When using netting, use a mesh size that is 1/32 inch or smaller.  Start using netting after early fruit set (so as not to interfere with pollination), but before fruit begins to ripen.  Make sure the mesh completely covers fruit with no gaps between sheets of netting or at the soil surface.  Any opening can provide an entry point for AFF.

Chemical control for AFF is not currently recommended in Wisconsin.  Observed AFF populations have not been high enough to warrant such treatments.  If spraying for AFF does become necessary, choose insecticides (e.g., spinosyns, carbamates and organophosphates) that also provide control of SWD.  As always, rotate active ingredients that are in different IRAC chemical classes (i.e., have different modes of action) to delay development of insecticide resistance.  For details on IRAC chemical classes, see https://www.irac-online.org/modes-of-action/.  Also, be sure to consider the effects of the products that you select, on non-target insects, particularly beneficial insects such as bees.  Please check the most recent Midwest Fruit Pest Management Guide (see https://learningstore.uwex.edu) for full product recommendations.

If you suspect that you have found an AFF, please contact the University of Wisconsin-Madison Insect Diagnostic Lab at (608) 262-6510, idl@entomology.wisc.edu or http://labs.russell.wisc.edu/insectlab/contact-us/.

For more information on African fig fly, as well as other vinegar flies:  See University of Wisconsin Garden Facts XHT1102 (Fruit Flies in the Home), University of Wisconsin Garden Facts XHT1237 (Spotted Wing Drosophila), or contact your county Extension agent.

Professional Guide to Emerald Ash Borer Insecticide Treatments

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)
  • Alpine (bifenthrin)
  • ArborMectin (emamectin benzoate)
  • AzaGuard (azidirachtin)
  • Boxer Insecticide-Miticide (emamectin benzoate)
  • Brandt enTREE EB (emamectin benzoate)
  • Dinocide, Dinocide HP (dinotefuran)
  • IMA-jet, IMA-jet 10 (imidacloprid)
  • Imicide, Imicide HP (imidacloprid)
  • Inject-A-Cide B (bidrin)
  • Merit 2F, Merit 75 WP, Merit 75 WSP (imidacloprid)
  • Onyx, OnyxPro (bifenthrin)
  • Pointer (imidacloprid)
  • Safari (dinotefuran)
  • Tempo (cyfluthrin)
  • Transtect (dinotefuran)
  • Tree-äge, Tree-äge G4 (emamectin benzoate)
  • Treeazin (azadirachtin)
  • TreeMec Inject (emamectin benzoate)
  • Xytect 2F, Xytect 75 WSP, Xytect 10% infusible (imidacloprid)

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

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 Alpine, Onyx,

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, Brandt enTREE EB, 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

and/or

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 (www.emeraldashborer.info).  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:

For more information on controlling emerald ash borer:  See
http://labs.russell.wisc.edu/eab/
www.emeraldashborer.wi.gov or www.emeraldashborer.info,
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).

Is My Ash Tree Worth Treating for Emerald Ash Borer?

This factsheet addresses some of the most frequently asked questions regarding the treatment of ash trees for emerald ash borer (EAB), and the removal and disposal of infested trees.

High value ash trees are candidates for treatment for emerald ash borer.
High value ash trees are candidates for treatment for emerald ash borer.

When should I consider treating my ash tree for EAB?Based on current research, EAB treatments are suggested only for ash trees located within 15 miles of a confirmed EAB site, or for trees located within a quarantined area.  Insecticide treatments are not necessary for ash trees located outside of these areas.  Even within the 15-mile radius, not all trees should be treated.  Due to the expense of insecticide treatments for EAB, consider the value of a particular ash tree in relation to insecticide treatment costs before making any treatments.  Proper use of EAB insecticides can help maintain the health of high value ash trees over time.  Lower value ash trees are not ideal candidates for EAB insecticide treatments.

How do I know if my ash tree has value?  Ash trees can be a valuable part of the landscape.  A properly cared for ash tree can increase property value, provide environmental benefits such as runoff and erosion mitigation, and reduce electricity costs by shading a home.  Determining tree value can be subjective.  Qualities to consider when assessing value include (but are not limited to) a tree’s overall health, shape, location with respect to landscape design, and appearance through the seasons, as well as whether or not a tree provides shade.  A healthy ash that is properly located in the landscape, has a nice shape and good fall color, and provides shade has value.  An ash tree that is not healthy due to disease or insects, has poor shape or structural damage, is otherwise unattractive, or is in a bad location (e.g., near a power line) is of lower value.

How do I know if there are ash trees in my area that are infested with EAB?  The Wisconsin Department of Agriculture Trade and Consumer Protection (DATCP) keeps track of EAB infestations in the state.  Visit the Wisconsin DATCP Emerald Ash Borer Resource Guide website (http://datcpservices.wisconsin.gov/eab/) and view the interactive map.  You can also contact your local county UW-Extension office to see if EAB has been found in your area.

How do I know if my ash tree has EAB?  Symptoms of an EAB infestation can include canopy thinning starting in the upper portion of the tree, epicormic sprouting (i.e., formation of sprouts) along the trunk, bark splitting, and woodpecker damage.  These symptoms indicate general tree stress, and can be due to EAB.  However, they also can be caused by diseases or insects other than EAB.  Specific signs of EAB include D-shaped exit holes (~3/16 inch wide) in the bark of the tree, S-shaped larval tunnels and/or larvae (cream colored, up to 1½ inches long) beneath the bark, and adults (metallic green, ~3/8 inch long).  Visit the UW-Madison Emerald Ash Borer in Wisconsin website (http://labs.russell.wisc.edu/eab/) for additional information on the symptoms and signs of EAB.

If I decide to treat my ash tree, will I have to treat every year?  In most cases, yes.  Most insecticides registered for EAB management require yearly applications to effectively protect a tree.  Products containing the active ingredient emamectin benzoate, are labelled for two years of protection.  Products containing emamectin benzoate are trunk-injected insecticides intended for use by professional insecticide applicators (e.g., certified arborists).  Such products can effectively protect an ash trees if the tree is treated every other year.

Can I treat an ash myself or do I have to call an arborist?  If your ash is smaller than 47 inches around the trunk at chest height [i.e., 15″ diameter at breast height (DBH)], you may be able to treat your ash tree yourself.  University of Wisconsin Pest Alert XHT1181 (“Homeowner Guide to Emerald Ash Borer Insecticide Treatments”) provides a list of products currently available for homeowner use.  If you decide to treat your own trees, be sure to read and follow all label instructions of the insecticide that you select to ensure that you use the product in the safest and most effective manner possible.

In some situations, hiring a certified arborist to treat your ash tree may be more desirable.  Professionals have access to specialized application equipment and additional insecticides not available to homeowners.  They are also trained to measure trees accurately, and assess the overall health of trees.  The Wisconsin Arborists Association website (http://www.waa-isa.org) has a list of certified arborists in the state.

Note that the University of Wisconsin does not endorse any insecticide products, and does not recommend any professional products over those available directly to homeowners.

Am I allowed to treat an ash tree in my yard between the sidewalk and street?   The answer to this question varies from municipality to municipality.  In many cases, municipalities have treatment or removal and replacement plans already in place.  Contact your local town, village or city to determine an appropriate strategy for protecting your sidewalk trees.

How much does it cost to treat an ash tree for EAB?  A single tree that is 32 inches around at chest height (approximately 10″ DBH) can be treated with a granular or liquid soil drench homeowner product for about $20-35/year.  Larger trees will require a larger amount of product and costs will be higher.  Arborist treatment costs vary depending on tree size and location, the insecticide selected, and the application method.  Other arborist-specific site visit charges may apply as well.  Consult at least two arborists in your area to discuss treatment options and costs.  To make an accurate comparison among service providers, make sure you know what insecticide will be used, the method of application, and how often treatments will be made.  An arborist will not be able to determine the exact cost of treatment for your specific ash tree without a site visit, but an arborist should be able to provide you with a cost estimate for a typical ash tree.

Do I have to remove my ash tree if it is infested with EAB?  Applying protective insecticide treatments to a healthy ash tree to prevent an EAB infestation is the best strategy for managing EAB.  However, if a tree becomes infested and the infestation is detected early, you may be able to treat your ash tree to prevent further damage, and help the tree recover.  Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50% canopy thinning.  Insecticide treatments are not recommended for trees with greater than 50% canopy thinning; these trees should be removed.  Trees that become infested with EAB and are not treated will ultimately die and will need to be removed.

How much does it cost to remove an ash tree?  Typically, a small (less than 25 feet in height) ash tree may cost a few hundred dollars to be removed by an arborist.  Larger trees may cost $1,000 or more to be removed.  Individual factors (e.g., the proximity of the tree to structures, power lines, or other hazards) can significantly increase the cost of removal.  Tree removal costs also may vary from location to location in Wisconsin.  Ultimately, removing recently killed trees while they are structurally sound, rather than allowing them to deteriorate, may be safer and more cost effective.

How do I dispose of wood from an infested ash tree?  If you choose to remove an infested ash tree, check with your municipality to see if a wood disposal or utilization program is in place.  If you have a tree removed by a tree care service, the service may be able to handle the disposal of wood from the infested tree.  If you decide to use wood from an ash tree for firewood or other purposes, use it locally.  Transporting infested wood risks spreading EAB elsewhere in the state, and may be in violation of Wisconsin’s quarantine laws.  Information about Wisconsin’s firewood regulations can be found on the Wisconsin DATCP Emerald Ash Borer website (http://datcpservices.wisconsin.gov/eab/).

For more information on controlling emerald ash borer: 

Homeowner Guide to Emerald Ash Borer Insecticide Treatments

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)
  • Bayer Advanced 12 Month Tree and Shrub Insect Control II (imidacloprid)
  • Bayer Advanced 12 Month Tree and Shrub Protect & Feed (imidacloprid)
  • Bayer Advanced 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)
  • Optrol (imidacloprid)
  • Ortho Tree & Shrub Insect Control Granules (dinotefuran)
  • 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
Ortho Tree & Shrub Insect Control Granules (G) Dinotefuran Early-June to mid-June Granule (G)
Bayer Advanced 12 Month Tree & Shrub Insect Control II (D)

 

Bayer Advanced 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)

or

Granular (G)

Optrol (D) Imidacloprid Mid-April to mid-May

and/or

Early-Sept. to mid-Oct.

Soil drench (D)
Bayer Advanced 12 Month Tree & Shrub Protect & Feed II (D) Imidacloprid

+

Clothianidin

Mid-April to mid-May Soil Drench (D)
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 http://www.waa-isa.org 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:
http://labs.russell.wisc.edu/eab/
http://www.emeraldashborer.wi.gov or
http://www.emeraldashborer.info or contact your county Extension agent.  For a video demonstration of treating your ash trees using a systemic drench, see
http://labs.russell.wisc.edu/eab/2014/07/12/protecting-your-tree-from-the-emerald-ash-borer/.

Viburnum Leaf Beetle

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.  At present, VLB infestations are known from Kenosha, Milwaukee, Ozaukee, Washington, Waukesha, and Winnebago Counties.

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

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.

Control:

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; Bugwood.org)
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; Bugwood.org)

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.