Willie Chance

The Turfgrass Industry is Losing Two Important Products for Weed Management

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Patrick McCullough, Associate Professor, UGA

The turfgrass industry is officially losing Illoxan (diclofop-methyl) and Embark (mefluidide) in 2015.  These are two important tools in weed control programs with no comparable replacements.  The loss of these materials has significant implications for resistance management, seedhead control, and efficiently managing high quality turfgrass.

Goosegrass - John D. Byrd, Mississippi State University, Bugwood.org
Goosegrass – John D. Byrd, Mississippi State University, Bugwood.org

Illoxan (diclofop-methyl)

Bayer will not be reregistering Illoxan.  Unfortunately, the return on Illoxan sales was not worth the expenses of reregistration for the company.  Illoxan is a postemergence herbicide used for goosegrass control in bermudagrass golf courses.  This herbicide is one of the most effective chemistries for controlling goosegrass in greens, tees, fairways, and roughs.  More importantly, Illoxan is the only ACCase inhibitor used in bermudagrass turf and the loss of this mechanism of action may have significant consequences for resistance management. Goosegrass resistance to ALS inhibitor herbicides, specifically foramsulfuron (Revolver), is becoming more widespread throughout the Southern U.S.  Turf managers also have restrictions on MSMA use on golf courses that limit the ability to effectively control goosegrass and other weeds.

Illoxan is an excellent herbicide for controlling goosegrass at most growth stages in bermudagrass and also offered an alternative mechanism of action in resistance management programs.  The implications of losing Illoxan in golf course management will emphasize the need for investments in good preemergence herbicides for goosegrass control.  Dinitroanilines (DNAs) like prodiamine (Barricade, others) and pendimethalin (Pendulum, others) have potential to control goosegrass but results are often erratic.  Resistance to DNA herbicides has also developed in goosegrass populations and alternative chemistries may be needed for effective control.  From our research at UGA, Ronstar (oxadiazon) and Specticle (indaziflam) have consistently been the best preemergence herbicides for controlling goosegrass in bermudagrass turf.  Other herbicides such as Dismiss (sulfentrazone), Sureguard (flumioxazin), and Tower (dimethenamid) have potential to control goosegrass but our results have been inconsistent over years.

With the loss of Illoxan, bermudagrass managers will only have Revolver (foramsulfuron), Tribute Total (foramsulfuron + thiencarbazone + halosulfuron) and Dismiss (sulfentrazone) available for postemergence goosegrass control.  While these herbicides may control immature goosegrass, single applications often do not control tillered plants.  Revolver and Tribute Total are both ALS inhibitors and will not effectively control mature goosegrass or resistant biotypes.

Turf managers may also explore the use of MSMA + Sencor (metribuzin) for goosegrass control but these treatments can be very injurious to bermudagrass in summer and may require sequential applications.  Moreover, superintendents in Georgia are limited to one application of MSMA per year, not to exceed 25% of the total golf course.  Turfgrass managers must understand that losing Illoxan may limit their ability to control goosegrass and may have serious repercussions in resistance management programs.

Embark (mefluidide)

Embark is a growth regulator primarily used for annual bluegrass seedhead control in turfgrass management.  Earlier this year there was controversy around the future manufacturing of mefluidide, the active ingredient in Embark, and if this product would be available after 2015. PBI Gordon explored opportunities inside and outside of the U.S. to have mefluidide manufactured and formulated to make new Embark products.  The opportunity to make new material was very costly for the company and PBI Gordon has decided not to pursue this investment.  The Embark 2S product will be pulled completely, and there will be new Embark T & O 0.2L (essentially a dilution of the 2S) released until the current supply is gone.  Once the existing inventory has been sold, Embark will no longer be available from PBI Gordon.

Embark is a growth regulator that has a long history of use in turfgrass and roadside management.  Embark is the only seedhead inhibiting growth regulator available for use in warm and cool-season turfgrasses.  Turfgrass managers primarily use this chemistry for seedhead control on annual bluegrass, tall fescue, bermudagrass, and other turfgrass species.  Proxy (ethephon) is the other seedhead inhibitor available for turfgrass.  It is labeled only for cool-season grasses but may be applied to certain zoysiagrass varieties.  Proxy causes leaf chlorosis, stand thinning, and quality reductions in bermudagrass, seashore paspalum, and other warm-season species.  Other PGRs like Primo (trinexapac-ethyl) or Trimmit (pacloburazol) may provide partial seedhead control but are generally less effective than Embark and Proxy.

Current research efforts at UGA include evaluating seasonal application timing of PGRs to minimize injury and maximize seedhead control on warm-season grasses.  We are also evaluating alternatives to Embark, primarily ALS inhibitor herbicides, for seedhead management in bermudagrass turf.  Embark is the most popular PGR for annual bluegrass seedhead control in bentgrass greens in Georgia and further research will be needed with Proxy, Proxy + Primo, and other compounds to replace Embark.

Patrick McCullough is an associate professor and extension specialist in turf weed science at the University of Georgia in Griffin.

What is this winter weed that shows up every year at this time?

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Florida betony plant
Figure 1 – Flower and foliage of Florida betony.

This weed is Florida betony. It is also called rattlesnake weed.

The publication Controlling Florida Betony in the Landscape gives cultural and chemical controls for this weed in lawns and landscape beds. The authors are Mark Czarnota, Ph.D., and Tim Murphy, Ph.D., Weed Control Specialists. Departments of Horticulture and Crop Science

Click here to see the publication for the following information:

Florida betony (Stachys floridana) (also called rattlesnake weed and hedge nettle) is a problem weed in both turfgrasses and ornamentals.

Florida betony tubers
Figure 2 – Tubers of Florida betony that look like the rattle of a rattlesnake, hence the name “rattlesnake weed.”

Florida betony is a “winter” perennial and, like most plants in the mint (Labiatae) family, has a square stem with opposite leaves. Flowers are usually pink and have the classic mint-like structure (Figure 1). Unlike its relatives, it has the unique characteristic of producing tubers that look like the rattles (buttons) of a rattlesnake, hence the name “rattlesnake weed” (Figure 2).

Click here to readthepublicationn Controlling Florida Betony in the Landscape

Georgia Urban Forest Council Landmark and Historic Tree Registry

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The tree that owns itself, Athens, GA Image from Wikipedia - Original uploader was Bloodofox at en.wikipedia
The tree that owns itself, Athens, GA Image from Wikipedia – Original uploader was Bloodofox at en.wikipedia

Taken directly from the GUFC website. See this link for all information

Background

The primary purpose of the register is to locate, document and compile a record of all of the significant trees across Georgia.  The register will also enhance our ability to educate and encourage the public and decision-makers about the importance of trees and the need to care for and protect them.

If you go to the map, clicking on a tree will give you some information about it, as well as a picture of the tree.  To view the trees in list form, go to tree list.

View Landmark and Historic Tree Map

Nominate

Nominations are accepted throughout the calendar year, with announcement of additions to the Register at the Fall GUFC Annual Meeting.   If you would like to nominate a tree please download the landmark-historic-tree-application

The GUFC website also has a link for Other Databases listing historic trees.

Southern Nursery Association Research Conference Proceedings Now Available

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SNA 2014 logo 22014 SNA Research Conference Proceedings Now Available 
The Proceedings of the 59th Annual SNA Research Conference are now available on the SNA website. Proceedings from 1991 to 2014 (2,986 titles comprised of 11,880 pages) are available in Portable Document Format (PDF) for downloading and viewing or printing. See list and links for each year’s proceedings.

For a complete list of proceedings (1991 – 2014) go to www.sna.org/page-1052564.

For the 2014 SNA Research Conference Proceedings go to www.sna.org/page-1736088.

READ MORE about the SNA Research Conference.

Take a look … there’s a lot of useful information!

What are the best post-emergence herbicides for annual bluegrass control in turf?

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Annual bluegrass - Robert Vidéki, Doronicum Kft., Bugwood.org
Annual bluegrass – Robert Vidéki, Doronicum Kft., Bugwood.org

Postemergence Annual Bluegrass Control in Turf

Patrick McCullough, Extension Weed Specialist, University of Georgia

Edited from a more complete article which can be found here.

Contrary to its name, both annual (live for one season) and perennial (live for many seasons) populations of annual bluegrass may be found in turf.  Annual bluegrass may out-compete other turf species during late fall and early spring.  Annual bluegrass often dies from summer stresses but may survive if irrigated – especially the perennial biotypes

Postemergence Control (See Table 3)

Annual bluegrass may be selectively controlled with postemergence herbicides (Table 3).

Landscapers managing warm-season grasses have more options for selective postemergence annual bluegrass control than cool-season grasses.

Flazasulfuron (Katana), foramsulfuron (Revolver, Tribute Total), rimsulfuron (TranXit), and trifloxysufluron (Monument) are labeled for bermudagrass and zoyiagrass non-residential commercial lawns and other sites.  Flazasulfuron and rimsulfuron are also labeled for use in centipedegrass. Efficacy of these herbicides generally increases under warm temperatures in spring compared to winter and non-ionic surfactants may enhance efficacy.

Pronamide (Kerb) is a restricted use herbicide for annual bluegrass control in non-residential bermudagrass, centipedegrass, St. Augustinegrass, seashore paspalum, and zoysiagrass.  Pronamide is root-absorbed and must be watered in following applications.  Pronamide efficacy is generally slower than most sulfonylureas and activity for annual bluegrass control may take approximately four to six weeks.

Atrazine (Aatrex, Bonus S, others) and simazine (Princep, WynStar, others) may also be applied to bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass for selective postemergence annual bluegrass control.  These herbicides often provide erratic control of annual bluegrass but may control other grassy and broadleaf weeds.  Actively-growing bermudagrass is sensitive to atrazine and applications are recommended only during the late fall and winter months.

Dormant bermudagrass may be treated with nonselective herbicides, such as glyphosate (Roundup, Touchdown, others), glufosinate (Finale), and diquat (Reward).  These herbicides will injure or kill existing vegetation, including annual bluegrass and managers should only spray at peak dormancy when no green turfgrass foliage is observable.  Nonselective herbicides should only be applied to completely dormant bermudagrass and applications during early spring may delay greenup with significant turf injury.

Flumioxazin (Sureguard) is a new herbicide for pre- and postemergence annual bluegrass control but applications are limited to dormant bermudagrass only.  Flumioxazin use after greenup or on other species are not recommended due to excessive injury potential.

Selective annual bluegrass control options in cool-season lawns are limited.

Ethofumesate (Prograss) controls established annual bluegrass in perennial ryegrass, tall fescue and dormant bermudagrass (see the current edition of the Georgia Pest Management Handbook). Two or three ethofumesate applications may be applied in late fall at three- to four-week intervals. Annual bluegrass control may be seen that fall, but control is usually observed the following spring. Annual bluegrass control with ethofumesate may vary greatly over years depending on environmental conditions.

Amicarbazone (Xonerate) is a new Photosystem II inhibitor, similar to triazine herbicides, but may be used in tall fescue lawns and other cool-season grasses.  Applications of amicarbazone in Georgia are limited to springtime only to minimize injury to cool-season grasses.  Warm-season turf is very tolerant to amicarbazone and may be treated at any seasonal timing.

Bispyribac-sodium (Velocity) has shown potential for selective annual bluegrass control in tall fescue and perennial ryegrass lawns.  However, this herbicide is currently registered for creeping bentgrass and perennial ryegrass on golf courses and sod farms only.  Spot treatments of nonselective herbicides are generally the most effective treatment regimen for annual bluegrass control in cool-season grasses.

Table 3.  Efficacy of postemergence herbicides for annual bluegrass control in turfgrass.

Common Name Trade Name (Examples) Efficacy
amicarbazone Xonerate F-G
atrazine Aatrex, others E
bispyribac-sodium Velocity F-G
flazasulfuron Katana G-E
flumioxazin Sureguard F-G
foramsulfuron Revolver E
glufosinate Finale E
glyphosate Roundup, others E
imazaquin Image P-F
metribuzin Sencor G
pronamide Kerb E
rimsulfuron Tranxit E
simazine Princep, others G-E
thiencarbazone + foramsulfuron + halosulfuron Tribute Total G-E
trifloxysulfuron Monument E

E = Excellent (90 to 100%), G = Good (80 to 89%), F = Fair (70 to 79%), P = Poor (<70%).

For more information

Annual Bluegrass Control in Residential Turfgrass

Annual Bluegrass Control in Non-Residential Commercial Turfgrass

New UGA Facebook page for nursery growers

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Nursery facebook pageDr. Matthew Chappell, UGA Nursery Specialist, has started a Facebook page for nursery producers.  Interested readers can “like” the page for timely information. This is the Facebook page description:

Here you will find updates on events, research, news and occasionally gossip related to commercial nursery production in GA and other states across the southeast.

To find the page visit Facebook page for nursery producers.

The Trial Gardens at UGA announces 2014 Classic City Award Winner Plants

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Merritt Melancon, News Editor with the UGA College of Agricultural and Environmental Sciences

John Ruter, Director of The Trial Gardens at the University of Georgia and Professor of Horticulture at UGA

See original article with photos here.

Each summer the staff of The Trial Gardens at UGA selects an all-star team of plants that performed spectacularly well during the growing season.

“These Classic City Award winners are the very best plants in the trial gardens, based on year-round performance and/or eye-clutching beauty,” said John Ruter, University of Georgia horticulture professor and the gardens’ director. “We raise thousands of plants each year, and these are the best of the best.”

Since 1982, The Trial Gardens at UGA have been used as a literal testing ground for plants from around the world. By evaluating new selections of annuals and perennials, the Trial Gardens’ staff helps introduce new plants to the Southeast’s green industry and the general public.

The Trial Gardens’ plant evaluations are respected across the globe. Commercial nurseries depend on the staff’s recommendations to determine what they will grow for sale the following season.

Many of the Classic City Award-winning plants are available for sale now, but others will be available through nurseries next season. Gardeners should ask their local nurseries to stock them.

For more information about the Trial Gardens and this year’s trial results, visit ugatrial.hort.uga.edu.

2014 Classic City Award Winners (Commentary provided by trial supervisor Meg Green and gardens’ director John Ruter)

  • ‘Archangel Dark Rose’ Angelonia– Ball FloraPlant “This Angelonia stood out amongst the others. It started out early by out-blooming its competitors and has remained strong through the hottest temperatures. The plants are compact and sturdy.”
  • Calibrachoa ‘Superbells® Frostfire’ “Our Calibrachoas were a bit slow to bloom in early summer, however, once the flowering began, it was profuse. ‘Superbells Frostfire’ has outshone other Calibrachoas, producing countless white flowers with a yellow eye. These plants remained compact while other Calibrachoas became spindly and scraggly late in the summer.”
  • Catharanthus Cora™ Series “We had 14 colors of the Cora series of Catharanthus this summer and every one of them performed outstandingly. The plants were consistent in height and floriferousness. All tolerated the heat, humidity and irregular rains quite well.”
  • Coreopsis ‘Sunshine Suzie’ “‘Sunshine Suzie’ is not a loud plant that begs for attention, but more of a quiet surprise. The plants were compact but airy, and were constantly in nickel-sized, yellow flowers. Month after month, ‘Sunshine Suzie’ excelled in our climate.”
  • Echinacea ‘Sombrero™ Adobe Orange’ “‘Sombrero Adobe Orange’ has completely wowed us with its extraordinary beauty. The plants produced numerous large, bright orange, cone-shaped flowers. This cultivar bloomed longer than any Echinacea we have grown ever.”
  • Euphorbia ‘Star Dust Super Flash’ “Over the years, the Euphorbias have performed well in our garden. ‘Star Dust Super Flash’ outperformed the others this summer. Countless small, white flowers covered the compact plants from April through October. The plants were well behaved, not falling over, nor infringing on their neighbors.”
  • Impatiens Bounce Pink Flame “This year was a great one for our New Guinea Impatiens. So many cultivars performed extraordinarily well, including the series ‘Big Bounce’ and ‘Bounce.’ In particular, ‘Bounce Pink Flame’ grew tall, but never lodged (or bent).”
  • Heliopsis ‘Sunstruck’ “‘Sunstruck’ Heliopsis grew to a mere 6 inches in height. Its leaves are variegated and they accentuate the large, yellow flowers well. These plants withstood our heat and humidity and performed beautifully.”
  • Hibiscus ‘Royal Gems’ “‘Royal Gems’ Hibiscus has been in our garden for several years and it has impressed us this long. The plants resist the insects that decimate many other Hibiscuses. ‘Royal Gems’ produces giant, deep rosy-pink blossoms for several weeks throughout summer. Its foliage remains a healthy, lush green until frost.”
  • Lobularia ‘Bicolor Pink Stream™’ “Month after month, ‘Bicolor Pink Stream’ displayed its beauty and perfumed its environment, never surrendering to the Georgia heat. This Alyssum is truly an extraordinary cultivar.”
  • Pelargonium ‘Glitterati™ Ice Queen’ “‘Glitterati™ Ice Queen’ was grown in hanging baskets in our garden where they thrived in the hot, blazing sun. The variegated leaves did not brown in the sun, but remained healthy all summer. This geranium produced numerous orange-red blooms that were evenly distributed throughout the plants, thus creating a lovely, mounding appearance.”
  • Petunia ‘Supertunia® Morning Glory Charm’ “Petunia ‘Supertunia Morning Glory Charm’ performed perfectly through the hot summer. It quickly formed a mound of small, violet blooms with a large, white eye. This petunia was loaded with so many small blooms, even in the hottest months of the summer. It never ceased to be a perfect sphere of violet with only bits of green visible.”
  • Scaevola ‘Scalora Amethyst’ “This fan flower amazed us with its perfection throughout the summer. ‘Scalora Amethyst’ was another cultivar that was obviously a winner from early in the summer. The plants easily grew into a mat of blue blooms atop its foliage.”

Controlling Mushrooms and Other Fungi in the Landscape

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Controlling Mushrooms and Other Fungi in the Landscape

Mushrooms

Mushrooms are the visible structures of the unseen fungi growing in our landscapes. Think of mushrooms as the flowers and fruits of the fungi world. The mushrooms these fungi produce may cause a concern depending on where they are growing. Mushrooms and other fungal growths can be unsightly and are a concern since some may be toxic to children. They can be found growing in mulch, turf and landscape beds.

There are many types of mushrooms and other types of fungal growth including puffballs, stinkhorns and others. Slime molds, though not a fungus, can appear as a slimy, oily or powdery growth on lawns, mulches or wood.  To see pictures of each, click on the links in the previous two sentences.

Unfortunately, it is almost impossible to prevent mushrooms and similar organisms from growing. Many fungi get their energy from decomposing dead organic matter. They are actually a part of the natural recycling process. There are no chemicals that effectively kill all the fungi that cause mushrooms. You can remove the mushroom, but you must remove the fungus to keep the mushrooms from returning. To remove the fungus, you will need to remove the organic matter upon which it is growing.

Control of Mushrooms

There are several possible sources of food for fungi:

  • Buried wood, roots or other organic matter. Dig up and remove the source.
  • Thatch under lawns. De-thatching and aerating the lawn may reduce mushrooms.
  • Mulch, especially mulch that is too thick. (Greater than 3 to 4 inches in depth).
  • Piles of leaves, logs and limbs. Remove them if you need to discourage mushroom growth.

Even if you remove the food source, the mushrooms may still continue to grow. Removing the food should help to some extent. Mulches can be removed, properly composted and used again.

Some mulches are more prone to producing mushrooms and other fungal growth. Proper mulch selection, application and care can reduce mushroom problems.

  • Bark chips from mature, old pine or cypress trees decay more slowly and are less prone to mushroom problems than chips from other types of trees. However, this is only true of chips from old, mature trees. Chips from young pine or cypress trees do not have this advantage.
  • Wood or bark mulches from hardwood trees can be more prone to fungal problems than bark mulches from old pine or cypress trees. Composting these mulches before use will help reduce the chance of producing mushrooms.
  • Mulches from bark or wood products should be composted for at least 6 months before being used as mulch. Add a nitrogen source to the mulch and keep the mulch moist and turned during composting
  • Do not allow mulches to get dry. This leads to an increase in fungal activity. Then when the mulch gets wet again, mushrooms appear. Apply mulches 2 inches deep and wet the mulch well at application. Keep the mulch moist but not overly wet.
  • Finer textured wood or bark mulches can be more prone to problems. Use coarser textured mulches and/or apply mulches in a thinner layer.

Mushrooms that grow at the base of trees (also called conks) are usually an indication that the interior of the tree is decaying. This can indicate that a tree is at risk to fall. If you see mushrooms (or conks) attached to tree limbs or roots, contact a certified arborist to evaluate the tree to see if has become a hazard.

Another fungal problem we see in mulch piles involves hydrophobic fungi. When mulch is applied too deeply or is piled up in areas, the mulch can be infested by these fungi that waterproof the mulch. Water will then no longer able to penetrate the mulch and the plant roots can dry out and die – even though the plants are being watered. This is especially a problem with woody mulches that are applied too deeply. Dig into affected mulches and you will notice that they are dusty dry. To prevent problems, do not apply these mulches more than 2 inches deep.

In addition, mulch piled against the base of trees can lead to tree damage and death. Pull mulches slightly away from the trunks of all trees and shrubs.

Once you begin seeing mushrooms, it may be best to just ignore or remove the mushrooms you can see and wait for the fungus to quit producing more mushrooms. This can take a while depending on the fungus, weather, etc. These fungal fruiting structures are often short-lived but interesting to watch. Try to ‘enjoy’ your landscape oddity until it runs its course.

 

Some information taken from Control of Nuisance and Detrimental Molds (Fungi) in Mulches and Composts from Ohio State University

Georgia Mosquito Control Association plans for threat of chikungunya virus next spring

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mosquito April Sorrow UGA
Georgia mosquito control professionals gathered in Athens this month to discuss the 2015 mosquito season. Image credit: April Sorrow, UGA.

Merritt Melancon is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.

As Georgia’s mosquito season draws to a close, mosquito control professionals are looking back, evaluating the season and planning for the challenges they will face next spring.

At the top of the list of concerns, voiced at the Georgia Mosquito Control Association (GMCA) meeting this month at the University of Georgia, was chikungunya, a viral disease spread by certain mosquitoes that causes severe joint pain and flu-like symptoms. Drawing on the lessons they’ve learned from battling West Nile Virus outbreaks for the last decade, mosquito control professionals are working with UGA entomologists and Georgia’s public health officials to stay one step ahead of the painful disease come next spring.

“The GMCA meeting is a great time for mosquito control professionals in Georgia to gather and share information about emerging threats and the best efforts to protect the public from these pests and diseases,” said Elmer Gray, UGA Extension mosquito specialist and board member of the Georgia Mosquito Control Association.

The disease is rarely fatal, but it is painful and, in some cases, has caused long-term joint pain, said Rosemarie Kelly, an entomologist with Georgia Department of Public Health.

It’s described as one of those things that, intellectually, you know you’re not going to die of, but you kind of wish you would,” she said.

The virus is spread person-to-person by container-breeding mosquitoes and was first diagnosed in the Western Hemisphere in December 2013. Since then it has spread prolifically in South America and the Caribbean.

In Georgia, there have been 21 travel-related cases of chikungunya reported to the state Department of Public Health since this summer. All of these patients had traveled on mission trips or vacations to Latin America and contracted it there.

It has yet to be spread from person-to-person in Georgia because the mosquito that spreads the disease most efficiently – the yellow fever mosquito, or Aedes aegypti – is fairly rare here. In Florida, where the yellow fever mosquito population is larger, public officials started to see locally transmitted cases of the disease this summer – 11 to date.

Even though the yellow fever mosquito is rare in Georgia, epidemiologists and entomologists are worried that the Asian tiger mosquito – an invasive mosquito that has spread to every county in the state – could also spread the virus.

Over the course of the three-day conference, mosquito control officials learned the importance of developing close relationships with their local health departments as well as how trapping and identifying mosquitos can help them determine where they need to focus mosquito eradication efforts.

In an ideal situation, mosquito control would be notified when someone is diagnosed with chikungunya, and they could work to knock down the mosquito population near that house to minimize the chance of it spreading, Kelly told the mosquito control and private pest control operators at the conference.

“The sooner you know about new cases, the sooner you get control of those mosquito populations, and the sooner you can stop the spread of the illness,” Henry Lewandowski, director of Savannah’s mosquito control program, told the crowd.

Georgians who are diagnosed with chikungunya or suspect they have it after returning from their travels should avoid mosquito exposure for 10 days. Ten days after the onset of symptoms, the virus will have left the body and can no longer be transmitted via mosquito.

As with West Nile Virus and other mosquito-borne diseases, the best defense is a good offense, Gray said. Gray recommends that Georgians routinely clear their yards of containers that can hold water, providing a breeding habitat for mosquitoes. He also recommends using a mosquito repellent containing DEET when spending time outdoors.

For more information about chikungunya, visit cdc.gov/chikungunya or search for “chikungunya” at dph.georgia.gov.

Understanding Formulations Used As Liquid Sprays

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From the publication Insecticide Basics for the Pest Management Professional

By Daniel R. Suiter, UGA Department of Entomology & Michael E. Scharf, UFL Department of Entomology and Nematology

 

Formulations commonly applied as liquid sprays are:

  • emulsifiable concentrates (abbreviated as EC)
  • wettable powders (WP)
  • suspension concentrates (SC)
  • microcaps (ME [microencapsulates] and CS [capsule suspensions])

 

These formulations must be diluted with water before they can be applied.

 

Emulsifiables are formulations that allow a water-insoluble insecticide to be suspended in water. Water and oil do not mix unless an emulsifying agent is added. When an emulsifier is added to a mixture of oil and water, microscopic droplets of oil are formed that disperse throughout the water. The resultant milky-white mixture is referred to as an emulsion.

 

Contact insecticides must be hydrophobic (insoluble in water) in order to penetrate the insect cuticle and/or interact with target sites. Although insoluble in water, most insecticides are soluble in oil or another solvent. To form an insecticide-active emulsion, the insecticide is dissolved in the solvent. When the emulsifier is then added, the resulting milky-white emulsion contains microscopic droplets of insecticide-impregnated solvent that become dispersed evenly throughout the water, as described in the previous paragraph. This resultant formulation can then be sprayed.

 

The droplets in emulsifiable formulations do not settle like suspensions and, therefore, require minimal agitation in comparison to formulations that are suspensions (wettable powders, microencapsulates, suspension concentrates).

 

Because emulsifiables readily absorb into skin, appropriate precautions should be used to minimize contact.

WP settling
Several liquid spray formulations (wettable powders, suspension concentrates, and microcapsules) form true suspensions, and will settle out of water when given sufficient time. In these photographs, a suspension concentrate was diluted in water at 4:00 p.m. (top photograph). The following morning, the solid, particulate matter had settled to the bottom of the glass beaker (bottom photograph), and required agitation to re-suspend the product.

Wettable powder formulations are created by impregnating or coating a microscopic particle of an inert carrier (e.g., adsorptive clay, talc, etc.) with insecticide and various inert ingredients to enhance the wetting, spreading, and dispersing characteristics of the powder.

 

The inert ingredients (wetting agents) allow the dry powder to evenly disperse in and mix with water without clumping or caking.

 

Because wettable powders are true suspensions, constant agitation is required to keep the powder suspended in water.

Wettable powders do not readily absorb into skin, but care should be taken when using this formulation to avoid accidental inhalation.

Suspension concentrates can be considered wettable powders that have been packaged in liquid formulation. They consist of very small crystals of technical grade insecticide mixed with an extremely fine, inert dust, a small amount of water, and various other inert ingredients. The inert ingredients enhance the dispersion and mixing characteristics of the formulation when diluted with water.

Because suspension concentrates settle out of suspension, they require constant agitation (Figure 1).

Microencapsulated products are formed by encapsulating an insecticide in a microscopic, round, plastic capsule. The capsules are mixed with inert ingredients (dispersants, wetting agents, etc.) to keep them from clumping and to help the mixture flow more readily. The inert ingredients also facilitate storage and dispersion when diluted in water.

The capsule’s wall thickness determines the release rate of the insecticide to the outside environment. The insecticide seeps through the capsule’s wall and coats the outside of the capsule. As the insecticide disappears (degradation, evaporation, etc.) additional insecticide inside the capsule continues to coat the capsule surface. This process maintains a capsule that is constantly coated with a thin film of insecticide.

The manufacturer can change the characteristics of the capsule wall to slow (or accelerate) the release rate of the chemical from inside the capsule, thus altering the residual life of the treatment. Changing the characteristics of the capsule can alter the product’s odor (slower release rates result in less smell); protect the chemical from environmental degradation; influence the rate of kill by the insecticide (faster release rates mean a faster rate of kill); and reduce exposure to non-target organisms.

Because microcaps settle out of suspension, constant agitation is required.

 

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