Rust Fungi in Eastern Red Cedar Trees

Elizabeth Little, UGA Extension Plant Pathologist

Each spring, as the leaves of Rosaceous plants such as apple, pear, and hawthorn are emerging, the Eastern Red Cedar (Juniperus virginiana) produces the bright orange fructifications of a group of rust fungi in the genus Gymnosporangium. Early spring rains induce the cedar rust galls to break hibernation and produce gelatinous orange protrusions that release basidiospores. However, these basidiospores do not re-infect the cedar tree but instead drift off to find the appropriate secondary Rosaceous host (like apple, pear, and hawthorn). On the leaves and/or fruit of the secondary host, the fungus will mate and produce a different type of brightly colored spores. These spores only infect the cedar tree and this infection results in the cedar galls that can take up to two years to mature.

Cedar apple rust
Image 1 – Cedar apple rust (top of image), hawthorn rust and quince rust

The most common and visible cedar rust is cedar-apple rust (G. juniperi-virginianae). Cedar-apple rust forms large round galls on the small branches of the cedar trees. (see image 1) The basidiospores produced by the galls infect the newly emerging leaves of apple and crabapple. On susceptible cultivars, the resulting leaf lesions can cause the leaves to fall during years of heavy infection. Fungicide sprays may help on susceptible trees. However, in the home and/or organic garden, the use of apple cultivars with resistance to both cedar apple rust and fireblight is highly recommended. Removal of cedar trees in the immediate area can help but may not be practical. Check the Georgia Homeowner’s Pest Management Guide for recommended treatments and cultivars.

Two other cedar rusts are common in Georgia, quince rust (G. clavipes) and hawthorn rust (G. globosum). The perennial galls of quince rust are formed under the bark on the cedar branches and are nearly invisible until the gelatinous protrusions emerge from cracks in the bark (see image 1). The spores produced by these galls infect the fruits of the apple, quince, mayhaw, and pear (see image 2). Hawthorn rust produces small inconspicuous galls on the cedar (see image 1). This rust infects the leaves and shoots of ornamental hawthorn.

Quince rust on pear
Image 2 – Quince rust on pear fruit

How close can I plant to a septic drain field?

Information taken from the UGA publication, Ornamental Plantings on Septic Drainfields by Sheri Dorn, Extension Horticulturist

Ornamental landscape plants are broadly grouped into two categories: woody ornamentals and herbaceous ornamentals. Woody plants usually have larger root systems than herbaceous plants and are more likely to interfere with septic drainfields.

Install woody plants an appropriate and safe distance from the septic drainfield. A good rule of thumb is to use the ultimate mature height of the selected tree as the minimum planting distance from the septic drainfield, then increase the distance. For example, if you are planting a crabapple, plant the tree at least 25 feet from the nearest drain line; 50 to 75 feet would be even better. Consider planting smaller and less aggressive cultivars, if possible.

Herbaceous plants, on the other hand, die back to the ground during the winter and include annuals, perennials and turf. Perennials, including turf, will return the next year from their roots, but annuals will have to be planted fresh each year. These plants are usually smaller in size and their root systems tend to be shallower and less aggressive than those of woody plants.

Both woody and herbaceous plants can be used when landscaping on septic drainfields as long as a few guidelines are followed. Remember that septic drainfield lines are often very shallow, some no more than 6 inches from the surface. Excessive digging, rototilling or other methods of soil preparation for planting can damage these lines.

Don’t choose plants that typically thrive in wet locations. When tree roots invade these septic drain lines, the extra moisture and nutrients favor root and plant growth, and lines become clogged and damaged.

Trees to Avoid on Septic Drainfield Plantings

  • Willow (Salix spp.)
  • Birch (Betula spp.)
  • Magnolia (Magnolia spp.)
  • Poplar (Populus spp.)
  • Elms (Ulmus spp.)
  • Some maples (Acer rubrum, Acer saccharinum)

Find other information on planting near septic fields in the UGA publication, Ornamental Plantings on Septic Drainfields by Sheri Dorn, Extension Horticulturist

Spring is a good time to manage Azalea Lace Bugs

Source – Will Hudson and Kris Braman, UGA Extension Entomologists

azalea lace bug and leaf injury
Azalea lace bug and injury, Pest and Diseases Image Library, Bugwood.org

Azalea lacebugs overwinter as eggs and hatch in the spring. Early spring is a good time to control them before they become too numerous.

Azalea lace bug attacks azaleas and some rhododendrons. Azalea lace bugs mainly feed on the undersides of the leaves, leaving the top of the leaf with white to yellow stippling or flecking. Heavy lace bug feeding on azalea can reduce plant vigor and flowering and affects the overall look of the plant.

Adult azalea lace bugs are 1/8 inch long. The transparent wings are held flat on the back. Their wings are lacy with two grayish-brown cross-bands connected in the middle. Nymphs begin life clear but quickly turn black and spiny. The flask-shaped eggs are partially embedded in leaf tissue, usually on the bottom of the leaf, and often are covered with a black tar-like secretion.

Look for the first signs of damage on plants in full sun or in protected areas beginning in March and continuing throughout the summer. Lace bugs overwinter as eggs. There are four generations a year. Lace bug adults and nymphs live and feed on the underside of leaves. Look for white stippling on older leaves. Look under leaves to find lace bug life stages and black fecal spots. On azaleas with a lot of damage, the top of the leaf can become grey or silvery.

Azaleas can withstand a lot of lace bug injury without much reduction in growth or bloom. The damage however on the leaves is unsightly. Control is generally recommended for the spring when insects are few in numbers. Treating early also protects the new leaves from damage from these insects. Once a leaf is damaged, the injury will be visible until the leaf falls off the plant.

Time spring insecticide applications for the presence of the first generation nymphs, usually with the early warm weather in late February in south Georgia through March and April in central and north Georgia.

Late summer insecticide applications are also helpful. Lacebugs overwinter as eggs and managing adults now reduces the number of eggs on plants and the number of lacebugs you will see next spring. Once lacebugs are in the egg stage, insecticides will not effectively manage them.

Cultural controls for azalea lace bugs

  • Plant azaleas only in partial shade. Too much sun stresses the plant and can make lace bug injury worse.
  • Keep plants healthy with proper planting, fertilizing and watering.
  • One of the best things you can do is scout azaleas (particularly early in the season) to identify and control infestations before numbers increase and leaf damage is severe.

Chemical Controls

Contact insecticides include the pyrethroids (bifenthrin, cyfluthrin, cypermethrin, permethrin, etc.) and carbaryl (Sevin and others) as well as other insecticides.

  • The biggest concern with contact insecticides is getting full coverage. The chemical must be applied to the underside of the leaves. This is difficult with larger, fuller plants.
  • You may need to make more than one application for full control. Check plants three to four weeks after the first application to see if they need another treatment. Knocking the branches over a white piece of paper should dislodge the lace bugs and make them easier to see.

Systemic insecticides

  • Some systemic insecticides may be used as soil applications (liquid drenches and granular treatments) as well as sprays. Soil applied insecticides enter through the root system and then travel into the leaves.
  • Foliar sprays of systemic insecticides tend to work more quickly than soil application but soil applications give a longer residual control – up to several months.
  • Even though some soil applied systemic insecticides may take two weeks or longer to become active in the leaves of large plants, this is not a problem if plants are small or if application is made early enough in the season to provide protection for the first flush of new leaves.
  • Read and follow all label directions since systemic insecticides differ in the way they work in the plant.

 

For more information:

For pest management information see the Pest Management Handbook (Follow all label recommendations when using any pesticide)

Contact your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office at http://www.caes.uga.edu/extension/statewide.cfm

Control of Lace Bugs on Ornamental Plants

Why are these annuals dying? What can I do?

Info taken from the UGA publication Crop Rotation and Cultural Practices Help Reduce Diseases in Seasonal Color Beds by Bodie Pennisi, Department of Horticulture and Jean Woodward, Department of Plant Pathology

Color bed disease fig 2 JWW-BPSeasonal color plantings can often appear healthy and beautiful one day and absolutely awful several days later. Total collapse at planting is not uncommon. Even though the chief culprit may be a particular disease, there are usually multiple causes at the root of the problem, all leading to plant demise.

Landscapers can reduce disease pressure in color beds by proper care:

  • Color bed disease fig 2 B JWW-BP
    Figure 2. Mixed planting and improper crop rotation in two consecutive years. The petunias are exhibiting signs of disease in the first year (upper photo) as well as the second year (lower photo).

    Choose plants suited to the sun and light conditions at the site. See this list of annuals with preferred growing conditions.

  • Prepare the soil in the beds to ensure both adequate water retention and drainage by incorporating several inches of organic matter each year.
  • Install annuals at a proper depth to avoid stressing root systems.
  • Remove old materials and spent blooms as much as possible to reduce disease inoculum.
  • Use water sensors on irrigation systems to provide water when it is needed, not on a specific schedule.
  • Choose water delivery methods, such as spray emitters directed at the base of plants, soaker hoses and drip irrigation, that will keep foliage dry.

Avoid planting the same species and cultivar of flowering crop, or crops belonging to the same family, in the same bed for more than two years. For example, petunias should not be followed with petunias because certain pathogens specific to petunias tend to accumulate and persist in the soil from year to year (Figure 2). Additionally, if ornamental tobacco is planted after petunia, it still could lead to plants being attacked by the same pathogens because the crops are closely related. This is of particular concern if the petunias were experiencing problems in the first year, which means that the pathogen is already in the soil and in sufficient quantity to cause damage.

Use the following list to select plants from different families to plant in successive years:

Common annual flowering species and their corresponding botanical family.
Family Name Common Name of Flowers
Amaranthaceae Celosia (Spike Celosia, Cockscomb), Alternanthera (Joseph’s Coat)
Apiaceae Parsley
Apocynaceae Vinca (Periwinkle)
Araceae Caladium, Alocasia, Colocasia (Elephant Ears)
Asteraceae Aster, Marigold, Gazania, Mums, Sunflower, Black-eyed Susan, Echinacea, Zinnia, Mexican Sunflower, Melampodium, Ageratum
Balsaminaceae Impatiens
Begoniaceae Begonia
Brassicaceae Alyssum, Ornamental Cabbage, Kale
Caryophyllaceae Dianthus
Commelinaceae Setcresea (Purple Heart)
Convolvulaceae Potato Vine (Ipomoea), Morning Glory
Crassulaceae Sedum
Geraniaceae Geranium
Goodeniaceae Scaevola (Fan Flower)
Lamiaceae Coleus, Salvia, Mints
Lythraceae Cuphea (Cigar Plant)
Plantaginaceae Snapdragon
Poaceae Grasses (e.g., Pennisetum)
Portulacaceae Portulaca (Purslane)
Rubiaceae Pentas (Shooting Stars)
Scrophulariaceae Angelonia (Summer Snapdragon), Torenia (Monkey Flower)
Solanaceae Petunia, Ornamental Tobacco, Ornamental Pepper, Browalia
Verbenaceae Verbena, Lantana
Violaceae Pansy, Viola

Find more information:

Crop Rotation and Cultural Practices Help Reduce Diseases in Seasonal Color Beds

Flowering Annuals for Georgia Gardens

Flowering Bulbs for Georgia Gardens 

Native Plants for Georgia Part III: Wildflowers

Landscape Plants for Georgia 

Success with Mixed Containers Using Perennial and Woody Plants

Get updated on fire ant baiting

Get updated on fire ant baiting

Article written by Mike Merchant, Texas A&M Agrilife Extension Entomologist, in his blog Insects in the City

Fire ants remain the most prevalent outdoor ant pest in most areas of the southern U.S.  Throughout the U.S. we estimate the annual cost of fire ant control at over $6 billion.  But the cost of this pest goes far beyond measurable dollars.  Fire ants reduce the recreational value of our parks and backyards, disrupt wildlife populations, and send thousands to emergency rooms each year from their painful stings.

So as we get ready to enter fire ant season, it may be a good time to bring yourself and your staff up to speed on fire ant control. Many people are surprised to learn that fire ants are not an especially difficult pest to manage, once the biology and control tools are understood.

One of the best places to learn about fire ant management is the eXtension fire ant website, a place where the best information about fire ant is assembled by Extension agencies throughout the South. This information was recently summarized and presented in an informative webinar by Dr. Fudd Graham, fire ant specialist with Auburn University.   Dr. Graham focuses on fire ant biology and use of baits for fire ant control.

It’s worth knowing something about how fire ant baits work because they are the most economical, ecologically friendly, and effective control methods for fire ants. The webinar will provide you or your technician with an hour of training that should pay for itself many times over.


 

Mike Merchant is an entomology specialist for Texas AgriLife Extension. He works with pest management professionals, school facilities managers, extension volunteers, researchers and other extension professionals. His areas of specialty center on research on insects affecting man including spiders, scorpions, fire ants, termites and others. His program also focuses on training school maintenance professionals in principles of integrated pest management (IPM). His goal is to make schools healthier, cleaner places to study and live.

Wasps and hornets looking for a place to call home!

This information is taken from the publication Management of Insect Pests in and Around the Home by Daniel R. Suiter, Brian T. Forschler, Lisa M. Ames and E. Richard Hoebeke.

Hornets (Vespidae: Vespa spp.)

European hornet Suiter-AmesThe European hornet, Vespa crabro, was accidentally introduced into North America about the middle of the 19th century. It is a large eusocial wasp with the wings reddish orange and the petiolate abdomen brown and yellow striped. There are no native hornets in the U.S.

Habits: European hornets build large, above-ground nests, usually in trees. Similar to yellow jackets and paper wasps, European hornets build a new nest each year. Each Fall all hornets die, with the exception of several queens, which overwinter. The following Spring these overwintered, mated queens initiate the construction of a new nest. European hornets are attracted to lights at night. They are not attracted to human foods and food wastes, as are yellow jackets, but they can damage fruits, such as apples, while the fruit is still on the tree.

Interventions: If European hornets are found around the house at night, because these wasps will forage after dark and are attracted to lights, examine and change the lighting regime. Do not attempt to remove or treat a nest; call a pest management professional to remove nests near areas of human habitation or activity. For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at caes.uga.edu/publications.

Might Be Confused With: cicada killers, yellow jackets.

Mud Daubers (Sphecidae and Crabronidae: many species)

Mud dauber tubes Suiter-AmesLong, slender, solitary wasps 1 to 1.5 inches, with long, slender waists. Commonly glossy black or blue, some species with yellow highlights.

Habits: Builds series of four- to six-inch long vertical mud tubes on walls in areas protected from rain and adverse weather. Commonly found under eaves, decks, etc. Each tube comprised of individual cells housing a single larva and spider prey that wasp larvae feed on.

Interventions: Knock down dry mud nests with a broom and wash mud from wall with soap and water. For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at www.caes.uga.edu/publications.

Might Be Confused With: paper wasps, potter wasps.

Paper wasps (Vespidae: Polistes spp.)

Paper wasp 2 Suiter-AmesPaper wasp 2 Suiter-AmesPaper wasp Suiter-AmesLarge (1 inch), aggressive wasps when at their nest. Various species, but all build paper-like, multi-celled, inverted umbrella nests under rain- and wind-protected eaves where wasps can enter and exit easily.

Habits: Each Fall all wasps die, with the exception of several queens, which overwinter in an inactive form in a well-protected, secluded environment such as under and in fallen logs and other ground debris. The following Spring, queens initiate and build a small paper nest where they lay eggs. Paper wasps build a new nest each year. Colonies grow and reach peak size in the Fall, at which time the cycle repeats. Like other social bees and wasps, paper wasps are aggressive when protecting their nest, and may inflict a painful sting in its defense. Adult wasps are excellent predators in vegetable gardens, and are more docile when not protecting their nest.

Interventions: If nests are out of the way, leave wasps alone as they are highly beneficial predators. If desired, spray nest and wasps directly with an aerosol jet spray, or early in the year, before the nest contains too many adult wasps consider knocking down the nest with a long stick but be prepared – and able – to quickly flee the area as the nest is dislodged. Make certain no one in the area is allergic to wasp venom (stings). For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at www.caes.uga.edu/publications.

Might Be Confused With: mud daubers.

Potter wasps (Vespidae, but sometimes recognized as Eumenidae: many species)

Potter wasp and nest Suiter-AmesAlso referred to as mason wasps. Common species dark blue or black with yellow or white highlights on abdomen and/or thorax. Solitary. Common species 3/4 to 1inch. Strongly sclerotized.

Habits: This wasp builds characteristic, oval-shaped (1/2 to 5/8 inch diameter) nests that appear pot-like with a knob-like handle. Pots are ornate and constructed of mud, as if built by a mason.

Interventions: Knock down ‘mud pot’ nests with a broom and wash mud from wall with soap and water.

Might Be Confused With: mud daubers.

For more information see these UGA publications:

Management of Pest Insects in and Around the Home

Stinging and Biting Pests

Scale insects (& others) outside can lead to ant problems inside

This wax scale-infested holly could be the key to controlling ants around your customer's home.
This wax scale-infested holly could be the key to controlling ants around your customer’s home.

From the Insects in the City blog by Mike Merchant, Texas AgriLife Extension Entomologist

Ask most PMPs who specialize in structural pest control what they know about scale insects, and you’ll get a blank stare. Pest management techs are typically taught little about insect pests of plants, especially tiny, non-descript pests that are frequently well-camouflaged from all but the most highly trained observers.

This is a mistake. A well-trained commercial or residential pest control PMP needs to know about plant pests, especially scales and their cousins the aphids, whiteflies and mealybugs. The key reason is that scales are part of the ecosystem surrounding the home or business, and can play an important role in insect life coming indoors…especially when it comes to ants.

You know ants. Only one of the most important pest issues for the industry around the world. The vast majority of indoor pest ants are sugar-loving.  But these ants don’t get their sweet tooth from sheer gluttony (like us!); ants have evolved with a heavy reliance on sugary foods in the form of honeydew.

Honeydew is the sweet excretion product of many plant feeding insects, including scales, aphids, mealybugs, whiteflies and others. Most of us have experienced honeydew when parking a vehicle under a tree during the summer months. Those sticky drops all over the windshield were honeydew, or less delicately, insect poop.

Much like our obsession with sugar, ants have an interesting relationship with honeydew producing insects. It turns out that ants have been relying on the scale insects for so long that both scale and ant have become co-dependent. The ant gets a free, long-term, stationary food source. The scales benefit from the ants keeping down excess honeydew and mold on the old leaf, and even get protection from predators like lady beetles and parasitic wasps.

Ants that naturally feed on honeydew include carpenter ants, crazy ants, odorous house ant, Argentine ants, acrobat ants, rover ants and fire ants…and probably several others I’m forgetting at the moment.  If you’re battling any of these critters on a regular basis, you might need to know something about why ants are attracted to your accounts in the first place.  In many cases it probably has something to do with the presence of scale insects around the building perimeter.

Sticky, shiny leaves are one tip-off that scale-like insects may be feeding on your customers’ plants.  Also look for waxy crusts often associated with aphids, scales and mealybugs.  Honeydew
also serves to grow a black mold called “black sooty mold”, another unsightly clue to a problem.

aphid honeydew

A few years ago when industry giant (at the time) American Cyanamid was searching for an improved bait for carpenter ant control they turned to experts in insect honeydew for insight. Researchers found that mimicking some of the natural constituents of insect honeydew in an artificial bait was a good strategy for designing a more effective bait.

I’m not suggesting that all ants are attracted to your accounts just because of sugar-pooping pests, but I guarantee you that, when present, these insects will contribute to an ant problem. So what can be done? First of all, learn the signs of honeydew producing insects, and how to select some of the excellent control products on the market.

There’s a lot to learn about scale insects–more than I can cover here; but if you’re interested in learning a little more, check out this link to a PowerPoint presentation I gave on the subject.  The topic is scale insects and their control. I hope the pictures and notes will give you an interesting introduction to the subject and a taste to learn more.  Speaking of taste, I think I hear a KitKat bar calling my name.

Pesticides not to blame for bee woes?

Post taken from Insects in the City blog by Mike Merchant, Texas Agrilife Extension Entomologist

Honey bee image from Dan Suiterand Lisa Ames
Honey bee image from Dan Suiter and Lisa Ames

According to Science Daily, new research shows that imidacloprid, an insecticide often blamed for the decline of commercially managed honey bees, is not likely to harm honey bees at field realistic levels.  The three year study, conducted by Galen Dively and associates at the University of Maryland, supports the contention by many U.S. bee researchers that proper applications of this insecticide is not likely to be the sole, or major, explanation for colony collapse disorder (CCD).

Despite those who claim CCD is clearly the result of dangerous insecticides, the issues surrounding CCD are complex and technical. Much of the debate in the research community recently has centered on what constitutes “field realistic levels” of imidacloprid and its cousin insecticides, the neonicotinoids. Industry representatives have contended that recent critical studies, cited by environmentalists as justifying a ban neonicotinoids, were flawed because they were based on unrealistically high levels of the insecticides. Dively and colleagues tried to allay these concerns by feeding their bees imidacloprid in protein supplement patties at doses of 5, 20, and 100 micrograms per kilogram (parts per billion).  The lowest dose, 5 parts per billion, is generally recognized as field realistic based on several studies of pesticide concentrations in the nectar and pollen of treated crops. The insecticide-laced protein supplement was provided to the bees over a continuous 12 week period. Even so this was, the authors contend, a higher exposure scenario than would likely occur in agricultural settings, where the contaminated pollen and nectar is not likely to be present continuously.

As one of the first studies to look at honey bee colony health over multiple seasons, the results were more rigorous than previous research.  They did showed a significant negative effect on colony survivorship as dosage increased; however the lowest, field-realistic dose showed no significant impact on key bee health indicators, foraging or winter survivorship.  The major impact of higher imidacloprid exposure were increased broodless periods, caused by weak queens during late summer. Such effects could lead to lowered overwintering survival, a character of CCD.

Nevertheless, the authors conclude that while short term exposure to high imidacloprid levels (represented by 100 part per billion dosages in this study) in agricultural settings does occur, it is not likely to occur continuously throughout a crop cycle.  Also, data from the study showed that bees were efficient in metabolizing imidacloprid, so that short term spikes in insecticide levels in nectar were likely to be quickly diluted and eliminated by the bees. They concluded that while imidacloprid might be a contributing factor to some overwintering losses in bees, seed treated crops in particular were likely to have negligible effects on honey bee colony health.

In the ongoing debate over bee health, this is one piece of good news for pesticide manufacturers and users; but it will not be the final word. And it should not justify anything less than the utmost caution for pesticide applicators when they use neonicotinoid insecticides.

Hourly weather forecasts from the National Weather Service

Taken from the CASE website

The National Weather Service has a good graphical forecast tool for hourly weather variables available on their web sites.  You can get instructions for how to get one for your location at http://www.srh.noaa.gov/oun/?n=hourlyweathergraph.

hourly-forecast-parameters

The forecast has a number of parameters to choose from, including temperature, wind, humidity, rain and other forms of precipitation, thunder, and a variety of fire weather variables that you might need if you plan to do controlled burns.

 

The output of the forecast depends on what parameters you pick but generally looks like the image below.  The forecasts go out to six days from present, which should give you ample time to plan activities which are weather-dependent, like spraying pesticides or cutting hay.

Many of the private forecasting firms also provide hourly forecasts on their websites and using their apps on smartphones and tablets.

Follow herbicide label to avoid killing landscape plants and trees

phenoxy herbicide damage to willow oak trees2 Pugliese
Phenoxy herbicide damage to a willow oak tree. Image credit: Paul Pugliese.

Paul Pugliese is the agriculture & natural resources agent for the University of Georgia Extension office in Bartow County.

An herbicide designed to kill weeds in turfgrass can also kill neighboring trees and shrubs.

Herbicides in the phenoxy chemical class provide broadleaf weed control in lawns, pastures and hay forages. Some of the more common chemicals in this class include 2,4-D; MCPP; dicamba; clopyralid; and triclopyr.

Safe for animals but not always for trees and shrubs

These chemicals are considered very safe and leave very few toxicity concerns for animals. In fact, many of these herbicides are labeled for pasture use and allow for livestock to continue grazing without any restrictions.

Phenoxy herbicide damage to a willow oak tree. Image credit: Paul Pugliese.
Phenoxy herbicide damage to a willow oak tree. Image credit: Paul Pugliese.

However, pesticide labels should always be read and followed to determine if any special precautions should be taken for specific site uses.

Phenoxy herbicides provide selective weed control, which means they control many broadleaf weeds without causing damage to grass. Of course, each product is a little different and some are labeled for very specific turfgrass types, depending on their tolerance.

The label should be checked for application to a specific lawn type (tall fescue, bermudagrass, zoysiagrass, etc.). If the turfgrass isn’t on the label, don’t assume the herbicide can be applied to all lawns.

Unfortunately, phenoxy herbicides don’t discriminate between dandelion weeds or any other broadleaf plants, including many trees and shrubs. So, it’s very important to take extra precautions when applying these herbicides near landscaped areas with ornamental plants.

Wind and rain can spread herbicides

Consider the potential for drift damage to nearby plants and avoid spraying herbicides on a windy day. There is also the potential for movement of these herbicides through runoff and leaching in the soil. This is why the product label usually warns against spraying within the root zone of trees and shrubs and never exceeding the maximum application rates listed on the label.

Many homeowners and landscapers often overlook these label precautions. The information that is contained on the label can seem somewhat vague to inexperienced applicators.

The biggest misconception concerns where the root zone of a tree or shrub exists. The roots of mature trees and shrubs actually extend well beyond the drip line of the canopy. Research shows that absorption roots may extend as much as two to three times the canopy width.

Consider spot-spraying to target individual weeds rather than broadcasting applications across the entire lawn. And never exceed the labeled rate.

In landscapes that contain mature trees and shrubs, phenoxy herbicides may not be the best choice for weed control. These herbicides may be best reserved for wide-open spaces such as athletic fields, parks and pastures where tree roots are at a safe distance.

The high potential for herbicide damage to trees is another great reason to protect tree roots by providing a mulch zone that extends well beyond the drip line of the canopy. If you’re not trying to grow a manicured lawn underneath a tree, then there is no reason to apply phenoxy herbicides there for weed control.

Use the right herbicide for the job

Another way to avoid potential damage is to rely less on phenoxy herbicides. Other classes of herbicides have less potential to affect the roots of nearby trees and shrubs. Take the time to identify your weeds and choose a more selective herbicide rather than combination products that usually contain multiple chemicals in the phenoxy class.

Many pre-emergent herbicides can prevent weed problems in lawns. The key is to apply them at the correct time in spring and fall. Applying too early or too late often provides inadequate weed control and requires additional herbicide applications. Rotating pre-emergent herbicide classes will avoid the potential for resistant weeds. Also, be sure to apply water to the area according to the pre-emergent herbicide’s label to activate it in the soil.

For more information about the effects of phenoxy herbicides on landscape trees and shrubs, view the UGA Center for Urban Agriculture webinar at ugaurbanag.com/webinars. For assistance with weed identification and specific herbicide recommendations, contact your local UGA Extension office at 1-800-ASK-UGA1 or visit www.Georgiaturf.com.

You can also watch an online webinar on Effects of Phenoxy Herbicides on Landscape Trees and Shrubs by Paul Pugliese.