Landscape Alerts

Landscape Alerts & Updates | September 2019

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Insufficient production and storage of photosynthates during the fall transition into dormancy can translate to issues during spring green-up.  Drought stressed turfgrass in August 2016 (Left) was able to recover prior to dormancy following appreciable rainfall (Right). However, we are seeing drought-stressed turfgrass in September of 2019 and the dormancy transition is quickly approaching.  Photo by Clint Waltz, UGA.

Tips for managing drought stressed turfgrass as dormancy approaches

by Clint Waltz

During periods of hot and dry weather, certain modifications to your lawn maintenance practices will help to carry your turfgrass through periods of inadequate rainfall and reduce losses. The height of the warm-season turfgrass growing season spans from May to October. Given average conditions (regular rainfall and moderate temperatures), bermudagrass, zoysiagrass, St. Augustinegrass, centipedegrass, and other warm-season species respond quickly to cultural and maintenance practices such as mowing, fertilizing, aerating, topdressing, and weed management.  However, the summer of 2019 has delivered hot and dry weather with sporadic rainfall.  With fall approaching, now is the time to adjust your turfgrass management program to promote a smooth transition into dormancy and green-up next spring.

From mid- through late-summer rainfall across Georgia has been variable with some areas receiving timely rain and other areas being droughty.  Moisture stress in turfgrasses can be recognized in the early stages by a dull bluish-gray cast.  Additionally, take note of footprints and tire tracks in the turf that do not seem to rebound.  If you are in an area that has lacked rain, consider applying some irrigation to get the grass growing.

Dr. Clint Waltz, UGA Extension Turfgrass Specialist, suggests these tips for managing turfgrass as it transitions into dormancy:

  1. Raise the cutting height within the recommended mowing range
  2. Do not apply nitrogen containing fertilizers
  3. Modify herbicide programs during high temperatures and moisture stress
  4. Water deeply & infrequently
  5. Grasscycle
  6. Use water conserving and drought tolerant turfgrasses

Raise the Cutting Height

Turfgrass stress can be reduced by using a sharp mower blade and raising the cutting height by 1/2″ or to the tallest allowable height of the recommended mowing range during drought.  A clean cut also reduces moisture loss through wounds and minimizes entry points for disease.  Taller shoots promote deeper roots and a dense canopy can help to reduce ground surface temperatures and conserve moisture.  Grasscycling (mulching clippings versus bagging) can also help to conserve moisture.

Avoid Nitrogen Applications

As grasses move into dormancy they need to “harden-off”.  Nitrogen fertilization encourages new shoot growth which directs plant sugars, and other metabolites, away from storage organs (e.g. rhizomes, stolons, and crown).  These storage organs and sugars provide the energy for the grass to green-up next spring. By allowing the plant to harden-off and accumulate sugars in the storage structures, the grass is better able to survive winter stresses and recover next year.

Modify Herbicide Programs During High Temperatures and Drought

Many herbicides act upon plant growth processes and can be less effective during periods of drought when weeds are not actively growing. In addition, certain herbicides may cause damage to drought-stressed turf or non-target landscape plants due to volatilization and drift during high temperatures. Review your pesticide labels for specific information regarding temperature requirements, watering requirements, and proper application.

Water Deeply and Infrequently

The optimum watering schedule can be roughly determined by observing the number of days that pass between signs of moisture stress. Apply sufficient water to saturate the root zone to a depth of 6-8 inches.  Clay soils and sloped areas may require staggered watering intervals to allow time for water infiltration between cycles and prevent runoff.  Irrigating in early morning conserves water by reducing evaporation and drift.  A good practice is to align watering schedules with drought management rules so that in the event of a declared drought, the appropriate watering program is already in place.  The 2010 Water Stewardship Act permits lawn watering between the hours of 4:00pm and 10:00am.

Use Water Conserving and Drought Tolerant Turfgrass Cultivars

The University of Georgia Turfgrass breeding programs continue to make excellent strides in developing improved cultivars with low water use and high drought tolerance. For new installations or where turfgrass replacement is needed, look for improved cultivars such as TifTuf bermudagrass.  Visit www.GeorgiaTurf.com for more information on selecting turfgrasses.

Landscape Alerts & Updates | June 2019

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Photo by Clint Waltz, UGA.

Nostoc Algae in Turfgrass

Guest post by Clint Waltz, Ph.D., University of Georgia Turfgrass Specialist.
(Turfgrass Blog #4: 2019 Edition, June 10, 2019)

With the recent dry weather encouraging the use, and possible overuse, of irrigation systems then the recent tropical conditions – rainfall and humidity – I have had several pictures and questions about a jelly-like substance growing in the turf.  The jelly-like “stuff” is a Nostoc algae,a genus of cyanobacterium formerly classified as blue-green algae.  It has multiple common names like star jelly, witch’s butter, and others.

Under warm temperatures Nostoc may appear suddenly in lawns, and other turf areas, following a period of rain and can be an indication of overwatering.  In turf, it is generally on a site where the grass is growing poorly due to severe compaction, overwatering, or both.  It does not cause turf decline or death; it colonizes areas where it has favorable growing conditions and the grass was already thin.  Poor drainage and compacted soils create a favorable environment for Nostoc. It will dry-out if the water or rainfall diminishes but it has only gone into dormancy.  With enough moisture, it will come back to “life”.

In its hydrated, gelatinous, green state it can be a safety hazard.  It is slippery.  Be careful walking on it.  However, when it dries-out it can become restrictive to turfgrass growth.  Nostoc dries into a black crust that can prevent stolons from rooting, or “tacking”, into the soil, delaying turfgrass growth and spread.

Nostoc can be difficult to control.  To discourage its growth, encourage the growth of the grass.  Algae is less of an issue with an actively growing turfgrass canopy.  The first step is to check the irrigation system to make sure it is watering properly (i.e. not too regular or too much).  The turfgrass species we grow in Georgia perform better when grown on the slightly dry side, so scaling back the irrigation and adjusting the irrigation schedule will benefit the grass and can discourage the algae.

Improve internal soil and surface drainage.  Core aeration opens the soil, allows oxygen into the root system, and reduces compaction.  While allowing the soil surface to dry-out then breaking up the Nostic “crust” by scarifying the upper ¼- to ½-inch can break the algae into pieces and encourage its spread, it also permits the turfgrass stolons to root into thin areas and outcompete the Nostoc.  With proper irrigation and core aerification the grass can cover and eventually predominate the area where the Nostoc was present.

For more information on Nostoc Algae, contact your local UGA Extension Agent at 1-800-ASK-UGA1, or click below to find your local office information.

FIND YOUR AGENT
 

Controlling Moss and Algae in Turf, UGA Extension Circular #823.
https://extension.uga.edu/publications/detail.html?number=C823&title=Controlling%20Moss%20and%20Algae%20in%20Turf

Landscape Alerts and Updates | April 2019

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Spring Equipment Theft

Each spring, as the demand for landscape services swings into high gear, equipment theft escalates.  Several members of the Georgia Green Industry Association and the Georgia Urban Ag Council report having their businesses hit with equipment theft.  Criminals are stealing equipment in storage and on the job.

Here are some general equipment theft prevention strategies to consider:

  1. Train employees on company procedures to deter equipment theft.  In addition, discuss what to do in the event of a theft or robbery.
  2. Take inventory: Establish routine equipment inventory. Keep documentation and photo records of serial numbers and models.
  3. Parking strategy: Be strategic about where you park your vehicle on each jobsite or lunch destination. Park in well lighted locations visible to the work crew and avoid leaving equipment unattended in back lots or hidden areas that are conducive to theft. Position trailers so they aren’t easily accessed or swapped to another vehicle.
  4. Reposition vehicles on large properties: Avoid leaving trucks far away from workers on large properties and keep trucks close.
  5. Deterrents: Lock vehicles, trailers, trailer tongues, and secure equipment when unattended. Don’t leave keys in trucks or commercial mowers.
  6. Security Cameras: If site has security cameras park where equipment can be seen by cameras. Install security cameras and sensor beams on storage areas.
  7. Tracking Devices:  Install tracking devices on large equipment.
  8. Be Alert: Pay attention to suspicious activity.
  9. Insurance: Review your policy and ask your insurance provider about theft prevention.
  10. Communicate with local law enforcement about landscape equipment theft or suspicious activity in your area.

Professional organizations play an important role in helping to find solutions to the issues of equipment theft at worksites, offices, and storage facilities. Supporting these entities through membership and communication strengthens industry efforts to combat crime. The Georgia Urban Ag Council maintains a Twitter account titled “GA Landscape Thefts” to compile information, articles, and reports from owners and residents experiencing equipment theft. Armed with this data, the UAC hopes to assist law enforcement agencies, equipment manufacturers, and suppliers in determining a course of action to reduce losses.

Landscape Alerts & Updates | February 2019

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Diseases and Problems to Watch for in Winter and Early Spring

Guest Post by Alfredo Martinez

 

Microdochium Patch in Golf Courses.  When night temps dip below 50°F, Microdochium Patch (Fusarium Patch, pink snow mold) can be severe on new bentgrass and semi-dormant bermudagrass greens, and on greens overseeeded with Poa trivialis.  Patches begin as small reddish-brown spots that can grow and coalesce into large blighted areas.  White to pink mycelium (sometimes mistaken for Pythium or dollar spot) may appear during extended periods of rain and overcast weather.  Cultural controls are the same as those listed above for Yellow Patch.  Effective fungicides include products that contain azoxystrobin, fluoxastrobin, iprodione, metconazole, propiconazole, pyraclostrobin, thiophanate-methyl, triadimefon, trifloxystrobin, triticonazole or vinclozolin.

 

Slime Mold/Sooty Mold;Blackening observed in fully dormant zoysia and or bermudagrass after few rain events? We have received samples exhibiting olive green, gray to black molding affecting dormant tissue This condition is known as slime mold and /or “sooty mold” in other crops. The growth is superficial in nature. While the symptoms are worrisome, the condition does not affect turf further. Sooty mold is the result of secondary, saprophytic fungi and not considered a true disease. Sooty mold develops on dormant, senescing and/or damaged turf when prolonged wet, humid weather occurs. This symptomatology is probably going to go away as sunny, breeze weather resumes. This blackening should mow off rather quickly.

 

Yellow Patch (Rhizoctonia cerealis).Sporadic infections of R. cerealis(yellow patch) have been observed in ryegrass over-seeded bermudagrass turf swards and sport fields. The disease is rare in the state, but it thrives in extended periods of wet, cloudy weather. It is a cool-temperature disease (50 to 65°F). Disease development is significantly suppressed at temperatures lower than 45°F and greater than 75°F. Avoid excessive nitrogen fertilization in the fall or when the disease is present. Thatch management is essential for disease control. Maintain thatch at less than 0.5 inch. There are several fungicides that can be used to control the disease, however in the state, yellow patch usually does not warrant a fungicide application.

 

Dollar Spot Can Start Early:  The dollar spot fungus (Sclerotinia homoeocarpanow named Clarireediasp) can produce infections on warm season grass as soon as they start to green up. Additionally, dollar spot can continue to infect cool season grasses anytime temps are above 50°F but it is fully active between 60°F and 70°F.  Due to low temperatures, recovery of turf from dollar spot symptoms in late winter or early spring may take weeks rather than days.  Therefore, preventive control of dollar spot is important at this time of the year. Monitoring fertility is an important first step to controlling dollar spot. Excessive moisture on turfgrass foliage will promote dollar spot epidemics. Excessive thatch layers and compacted soil stresses the plants and slows turfgrass growth and recovery from disease.

Chemical control for practitioners: A variety of fungicides are available to professional turfgrass managers for dollar spot control including fungicides containing benzimidazoles, demethylation inhibitors (DMI), carboximides, dicarboximides, dithiocarbamates, nitriles and dinitro-aniline. Several biological fungicides are now labeled for dollar spot control. For a complete and updated list of fungicides available for dollar spot, visit http://extension.uga.edu/publications/detail.cfm?number=SB28

Alfredo Martinez is a University of Georgia Professor and Extension Plant Pathologist in the areas of turfgrass, small grains, and non-legume forages at the Griffin campus.

 

 

Tiny Topics – Garden Tools

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For our next post on “tiny topics” I want to visit the topic of garden tools. It is easy to take our tools for granted. I have visited gardens where trowels and shovels are just left in the elements. They rust, become lost in garden debris, and blades become dull. Take some time during this slow garden season to evaluate, repair and clean your tools. Stocking the Garden Shed is a wonderful publication if you need guidance on adding to your tool shed.

Tool shed at Woodstock Community Garden. Tool sheds are a great addition to the community garden.

It may be surprising to discover that how you use your garden tools can have an impact on disease management in the garden:

#1 Making improper pruning cuts or using a dull blade can damage plants and open up pathways for disease-causing organisms to enter your plant. Be diligent in your pruning skills and do not damage your plant. I have seen old pruners actually rip the bark off of a fruit tree because the cut wasn’t crisp. Keep those blades sharp.

#2 Using a tool on a diseased plant and then using that tool on another plant can spread disease, even if that tool is left for several days between uses. Bacteria, viruses, and fungal pathogens are easily moved and in part that count on that for survival. Fungal pathogens can produce structures called survival spores which can be viable for a long period of time. If you make a cut with pruners on a diseased plant or use a shovel to clean up diseased plant debris you could be unknowing transporting some of these spores to a clean, disease free plant.

It is worthwhile to disinfect your tools. Using a cleaning solution of 1 part bleach to 9 parts water is a recommended ratio for proper disinfection. You will find that getting into the routine of proper tool cleaning will be another piece of the puzzle in your integrated pest management system.

Happy Gardening!

Brown Patch and Pythium Blight

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Brown patch (caused by Rhizoctonia solani) and Pythium blight (caused by Pythium spp).

These diseases are often the most severe diseases for cool-season grasses, especially on tall fescue and ryegrass.

Pythium blight has the potential to cause significant damage to turfgrass quickly. The disease starts as small spots, which initially appear dark and water-soaked. Affected turfgrass dies rapidly, collapses, and seems oily and matted. White, cottony mycelia may be evident early in the morning.  The disease is driven by hot-wet weather, which correlates with increased stress on the turf. Similar environmental and cultural factors that encourage brown patch also promote Pythium. Therefore, cultural practices for control of brown patch will also help to minimize Pythium blight development. A correct diagnosis is essential because Pythium control requires specific fungicides.

Several fungicides are available for each of the diseases described above. Consult the Georgia Pest Management Handbook or the Turfgrass Pest Control Recommendations for Professionals (www.georgiaturf.com) for proper fungicide selection and usage. Read the label and follow proper guidelines.


Pythium blight on tall fescue (Photo Lee Burpee)

Brown patch can cause a foliar blight, which results in necrotic leaves and circular brown patches up to 4-5 ft in diameter. High soil and leaf canopy humidity, and high temperatures increase disease severity. Higher than recommended rates of nitrogen in the spring promotes disease. Management options include: avoid nitrogen application when the disease is active, avoid infrequent irrigation and allow the foliage to dry, mow when grass is dry, ensure proper soil pH, thatch reduction, and improve soil drainage.


Brown patch on tall fescue (Photos Alfredo Martinez)

For more information on Brown patch and Pythium visit http://extension.uga.edu/publications/detail.html?number=B1233

 

Gray Leaf Spot

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By Alfredo Martinez

Gray Leaf Spot


Figure 1 (left) and 2 (right). Gray leaf spot on St. Augustinegrass (images by Alfredo Martinez)

Gray leaf spot (Figure 2) is a fungal disease that affects St. Augustinegrass, perennial ryegrass and tall fescue in Georgia. The disease is particularly aggressive in St Augustinegrass. Hot, humid summer weather and high nitrogen levels can make turf susceptible to this disease. The fungus causing the disease is Pyricularia grisea.

Symptoms: The symptoms of gray leaf spot vary depending on the grass cultivar. On St. Augustinegrass, gray leaf spot first appears as small, brown spots on the leaves and stems. The spots quickly enlarge to approximately ¼ inch in length and become bluish-gray and oval or elongated in shape. The mature lesions are tan to gray and have depressed centers with irregular margins that are purple to brown. A yellow border on the lesions can also occur. In cool-season turfgrass, the symptoms are similar to those of melting out.

Conditions Favoring Disease: Gray leaf spot is favored by daytime temperatures between 80ºF to 90ºF and night temperatures above 65ºF. It is also found in areas with high nitrogen levels and that are stressed by various factors, including drought and soil compaction. This disease is most severe during extended hot, rainy and humid periods.

Disease Management Tips: Management practices that minimize stress and avoid rapid flushes of lush growth during the rainy season lessen the likelihood that severe gray leaf spot symptoms will develop. If irrigation is used to supplement inadequate rainfall, water infrequently but deeply.

Proper irrigation regimens should protect against symptoms of drought stress without increasing disease pressure by extending periods of leaf wetness. Excessive soil moisture and leaf wetness promote gray leaf spot. Irrigating in the late afternoon or evening should be avoided, as this prolongs periods of leaf wetness.

Proper mowing practices are most important for gray leaf spot management in St. Augustinegrass. This grass must frequently be mowed during the summer months to remove excess leaf tissue and keep the canopy open and dry. Mow the turf at the correct height for the designated turfgrass species and remove only one-third of the leaf blade per mowing. Collecting clippings reduces the spread of the disease when gray leaf spot symptoms are evident. Thatch layers should be removed if they are greater than 1 inch in depth.

St. Augustinegrass is especially sensitive to some herbicides. If possible, manage weeds using cultural management techniques and minimal amounts of herbicides. The timing of any atrazine application should be chosen carefully, as this herbicide can stress the grass, especially when temperatures may climb above 85 degrees F. Atrazine applications made before or during disease-favorable conditions increase the likelihood of severe gray leaf spot symptom development. Spot-treating trouble areas with the herbicide may also be considered. Herbicides should always be applied according to the label instruction

Fungicides are available to control the disease. Consult the current Georgia Pest Management Handbook — www.ent.uga.edu/pmh/.

A New Exotic Tick is Headed to Georgia

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by Nancy C. Hinkle, Ph.D.
Dept. of Entomology, Univ. of Georgia, Athens

Anyone who has lived in Georgia probably has experienced ticks, either on themselves or on their pets. The most common of the state’s 22 native tick species is the lone star tick. The American dog tick is the next most frequently encountered tick; even though it is called a dog tick, it can be found on mid-sized wildlife of all types – coyotes, foxes, raccoons, opossums, etc. Gulf Coast ticks seem to be increasing in prevalence and expanding their range. Deer ticks are not very common (the ticks typically found on deer are lone star ticks).

But there is a chance that we’ll be getting a new type of tick – as if we needed it. Last year a tick species that had never been found in North America showed up on a farm in New Jersey. Despite control efforts and a harsh winter, it successfully overwintered and in 2018 has already been found in Virginia, West Virginia, Arkansas, and North Carolina. Its mode of distribution is unknown, but this rapid spread bodes poorly for containment.

Originally from northeast Asia, this tick showed up in Australia and New Zealand over 100 years ago, where it has established and become a significant problem on cattle and sheep. Known as the “Longhorned Tick” (scientific name Haemaphysalis longicornis), it is capable of transmitting several disease organisms infecting livestock and humans.

Why is this tick of particular concern?

  1. It is not native to North America. That means there are no natural controls here to keep it in check – no predators or parasites to suppress its numbers. Also, our animals have not developed any natural resistance to it, so it is anticipated to thrive on both wildlife and livestock.
  2. Males are extraneous. This tick is parthenogenetic, meaning females reproduce without mating, so males are unnecessary. Of course, this means that a single female transmitted into a new area can start a new population, indicating that infestations can readily spread. And each female produces over 2,000 eggs, so populations can rapidly explode.
  3. Longhorned Ticks do well on a variety of hosts, wildlife as well as livestock. They should thrive on white-tailed deer and quickly spread to livestock. They readily feed on small ruminants, horses, dogs, cats, humans, and several common wildlife species.
  4. This tick is tolerant of a wide range of environmental conditions, but will flourish in the Southeast, which has climate similar to its native range. As has been shown, it successfully overwinters in New Jersey, Virginia and West Virginia, so may well be active year-round in Georgia.
  5. The Longhorned Tick is capable of transmitting several animal and human pathogens. Large numbers of ticks feeding on an animal can produce anemia, particularly in young animals.

Unfortunately this invader looks like many of our native ticks, small and brown before it feeds, then swollen and gray after it takes a blood meal. So what should Georgians be looking for to alert them to the Longhorned Tick? High numbers of ticks per animal. Because each tick can produce over 2,000 eggs, tick populations expand rapidly and frequently exceed hundreds per animal. If you find an animal with lots of ticks on it, pull off at least a dozen, put them in a small bottle with alcohol, and take them to your county Extension office. Tell them to send them to Dr. Hinkle in Athens and we will identify them for you (be sure to include your contact information). Then treat the animals to kill the remaining ticks (consult the Georgia Pest Management Handbook for recommendations on tick control).

We may not see Longhorned Ticks in Georgia any time soon, but we do not want to miss them if they do show up.

2018 Tropical Storm Alberto

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Guest Post Written by Pam Knox,

Long-time residents of Georgia may remember the devastating floods of Tropical Storm Alberto in July 1994. The rain was so intense that Georgia’s one-day rainfall record was set during that storm, with 21.10 inches recorded at Americus for a 24-hour period ending on July 6, 1994, as the storm stalled over the state. In spite of that incredible record and the resulting damage, the National Hurricane Center did not retire the name of Alberto. This year, Alberto is the first name on the list of Atlantic tropical storm names for the season which begins on June 1.

The latest 5-day outlook for the Atlantic tropical region from the National Hurricane Center indicates that there is an 80% chance of this year’s Tropical Storm Alberto to develop in the Gulf of Mexico in the next five days, even before the season officially begins. While it is not likely to bring extreme winds and storm surge to the area, it is expected to bring copious rain to an area that has already received up to six times as much rain as usual in the last week, covering most of Georgia except the northwest corner. Another six inches is expected across a wide area of Georgia in the next seven days from the slowly moving storm. While this is not likely to be as wet as the 1994 TS Alberto, the wind and rainfall are still going to cause tremendous problems for us here in Georgia, along the coast and inland across most of the state.

Now is the time to think about what you need to do to get ready for the rain, whether or not it organizes enough to be designated as a named tropical storm. If you have weekend activities planned along the Gulf Coast for this Memorial Day weekend, be prepared for intermittent heavy rains, gusty winds, high waves and rip currents in the water along the coast from New Orleans to the west coast of Florida. If you are inland, prepare for localized flooding which will be worse because the ground is already saturated in many areas. Move equipment and livestock out of low-lying areas. Expect some trees to fall because of the wet soil conditions, even if the winds are not that strong. This may mean blockage of roads or disruptions in power, so check your generators now if you need supplemental electricity for your operations. If water covers the road, do as the National Weather Service recommends and “Turn Around, Don’t Drown.” You won’t be able to tell if the road has been undercut or washed away, and water has a tremendous potential to move cars and trucks even when only a few inches deep. The Extension Disaster Education Network (EDEN) has several useful publications on preparation and recovery at https://eden.lsu.edu/educate/resources.

I have heard from a number of contacts that the rain and cloudy conditions over the past two weeks has caused a lot of problems for producers, leading to splitting blueberries, increased fungal diseases, slow growth of crops, and the inability to get into the field to do side dressing of corn, application of fungicides and other treatments, and planting. Unfortunately, I don’t see a shift in this current pattern, and above average rainfall is likely to continue for the next several weeks, although there will be some drier periods that may allow you to get work done.

For updated information follow @SE_AgClimate or on Facebook at SEAgClimate. An excellent source of updated weather information is the local National Weather Service office, but you can also get information from many commercial vendors and the National Hurricane Center. Do not count on your smartphone weather apps to give you the most current information, since many of them are only updated once or twice a day. Keep monitoring for changing conditions, since above average sea surface temperatures in the Gulf of Mexico could lead to a rapid drop in pressure and increase in winds as the center of the storm gets closer to land, or the storm could move in a different direction under weak steering currents.

If you have comments to share about how the current rainy and cloudy weather is affecting your work and your crops, please feel free to send them to me at pknox@uga.edu. I always like to hear how the weather and climate are affecting Georgia agriculture.

Pam Knox
Interim Director, Georgia Weather Network
Crop and Soil Sciences, CAES

Pest Alert: February Monitoring for Granulate Ambrosia Beetle

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Post authored by Paul J. Pugliesea and Shimat V. Josephb

aUGA County Extension Agent/Coordinator (Bartow County), Cartersville, GA
bAssistant professor, Department of Entomology, University of Georgia – Griffin Campus.

Fig. 1 Adult beetle (left) and “tooth pick” symptom (right)

Granulate ambrosia beetle, Xylosandrus crassiusculus (Mot.) [Previously known as the Asian ambrosia beetle]

Introduction: Granulate ambrosia beetle (Fig. 1) is a serious pest of woody trees and shrubs in Georgia. These tiny beetles were first detected in South Carolina in the 1970’s and have spread across the southeastern US.

Host plants: Woody ornamental nursery plants and fruit trees are commonly affected. In spring or even in late winter (around mid-February), a large number of beetles can emerge and attack tree species, especially when they are young. Some highly susceptible tree species include Styrax, dogwood, redbud, maple, ornamental cherry, Japanese maple, crepe myrtle, pecan, peach, plum, persimmon, golden rain tree, sweet gum, Shumard oak, Chinese elm, magnolia, fig, and azalea.

Biology: The female beetles land on the bark of woody trees. Then, they bore through the soft wood and vascular tissues (xylem vessels and phloem) of the tree. They settle in the heartwood and begin making galleries. Eggs are laid in these galleries. Adults introduce a symbiotic fungi into the galleries as a food source for the developing larvae.

Symptoms: The initial sign of infestation is presence of boring dust pushing out of the bark as “tooth picks” (Fig. 1). Severely infested trees with granulate ambrosia beetle may show symptoms of stunting, delayed leaf emergence in spring, and extensive defoliation.

Fig. 2 Timing is a key factor in effectively managing Granulate ambrosia beetle. Monitoring traps placed in early February are useful for the early detection of beetle emergence and infestation.

Monitoring and management: Once adults of granulate ambrosia beetle bore through the bark, there are limited control options to mitigate the problem. Those settled beetles in the heartwood of the tree are less likely to be exposed to insecticides. Also, the beetles do not consume the wood, which further minimizes their pesticide exposure. Pyrethroid insecticides such as bifenthrin or permethrin can be used as preventative sprays to repel invading females. Thus, the insecticide-application timing becomes critically important for management. The insecticide applications can be timed with trap captures or adult activity. The simplest method to determine adult activity in the area is using alcohol and a bolt of wood (Fig. 2). A wood bolt (about 2 to 4-inches in diameter and 2-feet long) can be utilized. Any hardwood species such as maple will work for building traps. A half-inch diameter hole drilled at the center of the bolt, about a foot deep, is filled with alcohol and the opening can be closed using a stopper cork.  Ethyl alcohol or grain alcohol with 95-percent alcohol content (190-proof) can be found at most liquor stores. Hang several bolt traps along the woodland border of a nursery at waist height to determine beetle emergence and activity. Sawdust tooth picks (Fig. 2) begin to appear on the bolt when they are infested with adult beetles. Once tooth picks are detected on a bolt trap, daily scouting should occur on nearby trees.

An immediate spray using a pyrethroid insecticide on nursery trees is warranted upon detection of tooth picks on the bolt trap.  Be prepared and ready to act quickly as soon as beetle activity is confirmed.  If practical, the entire nursery should initially be treated with an area-wide application to repel beetle activity.  If individual trees are found to be infested, immediately destroy infested trees and follow up with targeted spray applications in blocks with beetle activity. Generally, pyrethroids are not effective for more than a week as their residues quickly breakdown. Re-application of the insecticide is generally required at weekly intervals until spring green-up is complete in areas where the beetle pressure is moderate to severe.

Healthy trees can withstand a low level of beetle infestation. Timely irrigation and adequate fertilization of trees throughout the growing season will increase a tree’s tolerance to beetle infestation.  Closely monitor traps throughout the spring for a second emergence of ambrosia beetles. Ambrosia beetles can have multiple generations throughout the year and are strongly attracted to trees that are drought stressed, injured, or excessively pruned.  Pay close attention to irrigation needs during extended summer and fall drought periods to minimize tree stresses.  Avoid mechanical wounding of trees with maintenance equipment that could invite ambrosia beetles to attack.    

When to deploy monitoring traps: The monitoring traps should be deployed starting the first week of February in Georgia because warmer periods during a mild winter may trigger early beetle emergence and infestation.

References: 

  1. Frank, and S. Bambara. 2009. The granulate (Asian) ambrosia beetle. Ornamental and turf. Insect note. North Carolina State University.
  2. Wells. 2015. Managing ambrosia beetles. UGA pecan extension
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