Prevention and Management of Boxwood Blight

January 28, 2013

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by Kelly Ivors, Extension Plant Pathologist, Dept. of Plant Pathology, NC State University


This disease can significantly impact the appearance and aesthetics of boxwood because the foliage typically becomes blighted and drops from the plant. Symptoms of box blight include: dark‐ or light‐brown, circular leaf spots often with darker margins; dark stem cankers or black ‘streaks’ on stems; straw‐ to bronze‐ colored, blighted foliage; and leaf drop. Leaf spots may grow together to eventually cover the entire leaf (see pictures). In container boxwood, sometimes only the lower foliage and stems become infected, leaving the tops green and making the plant appear top‐heavy.On large field‐grown or landscape plants only one section of the plant closest to the ground on the shaded side will be blighted.

…full article found here.

Photos of Boxwood Blight found here.


OHP launches new Marengo® herbicide

December 18, 2012

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OHP Inc. is proud to announce the introduction of Marengo® Herbicide to growers in the production ornamental market.Marengo pre-emergent herbicide new mode of action MOA OHP Olympic Horticultural Products Marengo has received its federal EPA registration and is undergoing the state registration process.

Marengo, with the exciting new active ingredient indaziflam, is a selective pre-emergent herbicide that offers long-term residual control of both grassy and broadleaf leaves.

We are thrilled to add Marengo to our expanding herbicide portfolio,” notes Dan Stahl, OHP vice president of marketing and business development. “Marengo offers unparalleled residual control of many hard-to-control weeds with impressive plant safety.

Marengo contains the first active ingredient from MOA (Mode of Action) Group 29. The active ingredient prevents weed seed germination by inhibiting cellulose biosynthesis. Marengo does not move once applied to the soil and does not volatilize.

Marengo is registered for use on production ornamentals grown in outdoor nurseries, as well as on conifers, Christmas trees, and ornamental production sites and hardscapes. Marengo is labeled for use in shade houses and hoop houses as well.

Marengo offers extended broad-spectrum weed control of up to eight months in nurseries but also in extended use sites such as hardscapes and hoop houses,” notes Dave Barcel, OHP senior technical manager. “It’s extremely active at low use rates.

Marengo use rates range from 7.5 to 18.5 fl.oz. per acre depending on soil type and conditions.  It performs best when applied to bare ground or mixed with a post-emergent herbicide to eliminate existing weeds.

Marengo should be applied as a broadcast spray over ground areas and as a directed spray for field grown ornamentals.  Fall applications have shown excellent weed control through the following spring season.

Marengo will be packaged in one-half gallons, packed 4 to a case.

For information on current state registrations, click here.

OHP is a leading marketer of pest and weed control solutions to the production ornamentals market.

(Marengo is a registered trademark of Bayer.)


OHP adds Dr. Carlos Bogràn to tech team

October 31, 2012

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OHP Inc. announces the addition of Dr. Carlos Bográn to its team of horticulture professionals.

Bográn assumes the role of OHP Technical Manager with focus on fungicide and insecticide support and development.

He joins OHP after 11 years as assistant and then associate professor and extension specialist in the departments of entomology and plant pathology, and microbiology at Texas A&M’s AgriLife Extension Service in Bryan, TX. In that role, Bográn conducted applied research and directed state-wide education programs.

We are thrilled to add Carlos to the OHP family,” notes Dan Stahl, OHP VP of marketing and business development.

He brings unique skills to our company with his breadth of knowledge on insecticides and fungicides,” notes Stahl. “Plus he is fluent in Spanish which is critical in today’s world of horticulture.

Bográn holds a doctorate degree in entomology from Texas A&M University and a master’s degree in entomology from Iowa State University.

In his 18 years in agricultural research and extension, Bográn has authored close to 100 articles in industry and scientific journals and extension publications.

He will assume some of the duties of OHP Director of Technical Services Jeff Dobbs, who is retiring effective Dec. 31, 2012.

Jeff’s contributions to OHP are far-reaching,” notes Stahl. “We wish him all the best in his retirement.

David Barcel, OHP senior technical manager, will work in tandem with Bográn and continue to focus his efforts on herbicides and plant growth regulator (PGR) research and development.

OHP is a leading marketer of pest control solutions to the nursery, greenhouse and associated markets.


Terrazole still the most effective Pythium fungicide on Ornamentals

October 10, 2012

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IR-4 studies conclude that Terrazole remains the most effective fungicide on Pythium species attacking ornamentals. Aliette continues to perform.

“Source- Chase Research Newsletter October 2012”

Click here for full article. 






PGR’s for Woody Nursery Plants

March 9, 2012

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Do you need to use plant growth regulators (PGRs) in a traditional outdoor nursery? Let’s go back 10 years when the traditional plants grown in container nurseries were hollies, junipers and other hardwood plants, and the answer would probably be no. PGR use has been an increasing part of the greenhouse industry, primarily aimed at flowering plants.

Fast forward to today and many of the larger container nurseries have moved away from the traditional woody crops and are now focusing on flowering crops. Examples are the explosion of roses, hydrangeas, buddleias, sages and other blooming plants. While many of these are true perennials, they are being grown as annuals in more northern climates for mixed containers, such as dracaena spikes, which were rarely seen outside of tropical areas or interiorscapes. And many of the larger nurseries are now more than 50 percent color crops as opposed to traditional woody plants.

According to Joyce Latimer of Virginia Tech, most of the PGR questions she gets are from nursery operations. She credits this with the expanded production of blooming perennials and especially the use of PGRs on the less herbaceous crops like hydrangeas and roses. Another factor is that the greenhouse grower is more familiar with PGRs and has more established routines or programs.

New market
Many of the current and newly introduced perennials have a lot of color and are changing the marketplace. Most need some sort of help to increase flower production or shorten plants to aid in shipping and handling.

Rosemary plug treated four weeks after Augeo treatment. (L-R) 0 ppm, 400 ppm, 800 ppm, 1,600 ppm. Photo courtesy of Joyce Latimer

Since we don’t want our plants to look like they came from the ditch, we must use measures to improve quality. Growers can either use hand labor to pinch or trim plants, or explore the use of PGRs to increase the quality of their perennial and woody crops. Since quality labor is increasingly expensive, you may very well want to explore the use of PGRs for your crops. Most of the factors involved with these products hold true when used on either herbaceous or woody species, but not always. So seek advice before you begin using them.“I am now growing plants for sale that were weeds in the ditch growing up in southern Missouri,” said Matt Chambers of Stark Bro’s Nurseries in Louisiana, Mo.

A PGR primer
The commercial PGR products fall into six or seven different groups. The main mode of action group is the GA (gibberellic acid) inhibitors. These products inhibit the natural production of GA. All of these products act to hold or reduce internode stretch of plant stems. They can be divided into three basic groups based on their activity or residual action. Group 1 consists of Cycocel and B-Nine—they belong to the ammonium class and are considered as low level of activity.

A-Rest and Topflor belong to the pyrimidine class and are generally considered as medium level of activity.

The highest level of activity and residual action products are members of the triazole class. Common products are Paczol, Bonzi and Sumagic, and are generally used at very low ppm rates.

The cyclohexaketones are a relatively new class to the ornamental market. Augeo is a new product in this class. The function of Augeo is to trick the plant into thinking it has been pinched to release the lateral shoots. Unlike manual or chemical pinching, Augeo will cause slight yellowing in the apical tips but generally does not abort the tip or flowers. Augeo has been on the market for just a few years and work is very encouraging on perennials.

The third group is the fatty acids such as Off-Shoot O. Their function is to “burn” the tip tissue to perform a classic chemical pinch. Affected tissue generally browns up and then drops off similar to the effect of a manual pruning.

The GA class is generally regarded as growth promoters. The two main products are ProGibb T&O (GA3) and Fascination (a combination of GA 4+7 and benzyladenine). They can be used to correct an overdose of the GA inhibitors or to increase stem elongation where desired.

Ethylene promoters are classified as acids and increase ethylene production in plants. Florel formulations are the main products. They act to disrupt or over-ripen terminal tissues, thus releasing lateral buds. Care must be used if applied too close to flowering, as ethylene can abort flowers.

The rooting hormones are synthetic auxins. Major products are Hormodin and Dip N Grow. Auxins stimulate root production; therefore these products are used for rooting purposes. Herbaceous plants need just a little auxin to promote rooting, while woody plants will require higher levels of auxin to promote rooting.

Roses 4 weeks after Uniconazole treatment. (L-R) 0 ppm, 15 ppm, 30 ppm, 45, ppm, 60 ppm. Photo courtesy of Joyce Latimer

A new PGR under development is Con-Tego from Valent. It is an abscisic acid (ABA). It is being evaluated for its effect on leaf stomates, the pore cells found on the underside of leaf. By regulating these pores, the plant can withstand dry periods better. Simply stated, the plant needs less water. Commercial interest would be in extending shelf life for plants at the retail level.

While knowledge about using PGRs in nurseries is always expanding, there are numerous university sources of information available to growers including Virginia Tech ( and Michigan State

Paul Pilon offers extensive advice on the culture of perennials including PGRs in his book Perennial Solutions. OHP Inc. (formerly Olympic Horticultural Products) has also made its iPhone PGR calculator app and OHP PGR Solutions available free to growers.

Article by: Andy Seckinger