Impatiens Success Dependent On Landscapers, Homeowners

Downy mildew has been decimating landscapes full of impatiens in South Florida this year. Photo courtesy of Aaron J. Palmateer, assistant professor and extension specialist at the University of Florida.

As BASF’s Kathie Kalmowitz made her way across Florida in mid-February, she saw firsthand just how poorly impatiens were faring in landscapes. Every bed Kalmowitz saw was stripped of leaves, the result of a downy mildew pathogen gone wild.

Recently, Greenhouse Grower caught up with Kalmowitz, a technical expert who offers guidance to growers in need of getting downy mildew under control on America’s number one bedding plant.

GG: Why do you think the impatiens you saw in Florida earlier this year are struggling so mightily with downy mildew?

KK: I think the disease has simply been carried over in the soil from the previous year. When plants aren’t cleaned out and the residue is left to rot, the [downy mildew] spores are overwintering. So when the crop is replanted, the crop is coming into contact with those spores.

The key is for consumers not to plant impatiens where they had impatiens last year. Downies are very host-specific pathogens, meaning this particular downy goes to the walleriana impatiens. If you had a snapdragon with downy mildew or a rose with downy mildew, those pathogens would not move to impatiens.

GG: How fast is the disease spreading on impatiens in the landscape?

KK: Let’s say a tray has gone through the broker, a garden center and now it’s finally gone into the hands of a landscaper – so it’s probably been a couple weeks since it came out of the greenhouse. At that point, the last fungicide is starting to wear off. As beds are planted, you may all of a sudden see more typical symptoms of downy mildew – a little bit of a bronzing effect, or you turn the leaf over and see the fuzzy sporulation on the back of the leaf.

Still, I doubt if landscapers will be back in beds once they’re finished planting. By four weeks out of the greenhouse, the sporulation is taking hold and you see the plant start to defoliate. If you go back to a bed that was absolutely spectacular in color, all of a sudden you see sticks.

GG: What’s your impression of how growers are handling their own impatiens material in the greenhouse?

KK: I think the greenhouses are pretty clean. Growers are being cautious and putting out flats that are clean when they exit. But when impatiens are in a production greenhouse as plugs or as finished products, they’ve had at least two cover sprays. They’ve had a drench in the plug stage and at least one finished spray. So they’re clean going out, but impatiens probably also need a cover spray in the landscape.

GG: What advice can you offer growers looking for guidance as they try to manage their way through this particular pathogen?

KK: BASF has Stature SC fungicide for growers. This product, applied preventively, can stop sporulation of downy mildew, hence stopping the infection cycle. Stature is an excellent fungicide choice for growers as a last protective spray. We know garden centers are not going to apply fungicides. So it’s up to growers to provide at least the two-week window of greater protection once it gets out of their production greenhouses.

Additionally, there are things landscapers need to do. Landscapers should be responsible for putting a cover spray on, which they probably have not done in the past. They need to explain to their customers why because there’s going to be a cost built in.

If landscapers go back to a job and see that plants are already showing signs of infection (beginning to defoliate), they need to take those plants out immediately. They’re not going to save them. They need to remove them from the landscape and actually keep that residue isolated from any of their other beds.

Downy mildew is wind borne, so if you had an open landscape truck moving down the road, those spores could move off the material. Landscapers need to enclose the residue in a paper or plastic bag so they get the inoculum out of the environment.

GG: What can growers learn from the downy mildew on impatiens scene in Europe, where the issue has become an even bigger problem than here in the United States?

KK: Based on what I read from England, they thought the problem subsided. The truth is it’s an epidemic. I do believe it’s because England went through low years of not paying any attention that they’re struggling again.

For us, I think it’s going to take more than a one-year cycle in the U.S. to clean up our beds. The moral of the story is you have to watch how you plant impatiens. Even with a cover spray in the landscape, you could still get some disease in the newly planted beds. But you certainly can’t put new impatiens behind last year’s impatiens.

GG: If the disease persists in the landscape, could we be faced with a situation in which growers avoid Impatiens walleriana altogether in 2013?

KK: From the standpoint that I am with a chemical company with products like Stature SC fungicide and Pageant fungicide, we feel you can keep plants clean as you move from production into the landscape. But you have to choose to use the best products in order to produce the crop.

Now, because we know there may be a problem with how fast this disease can develop with the environmental conditions and other factors, I do feel the seed companies are going to try to steward this situation to the best of their abilities. If they feel their seeds are clean, then growers should still be able to plant the crop next year.

Leave a Reply

More From Annuals...

July 30, 2015

Let’s Talk About Starflowers. Why Is Pentas Not More Popular?

It is good to talk about production techniques, performance results and then to see how our friends garden. Diversity of plant material has always been a strength in American garden centers, and we should never run out of plants to get people excited. However, perhaps people are tired of Petunias or Callas or Geraniums, but we will never run out of options to put in front of them. One plant that is often overlooked is Pentas, a fabulous summer crop for late spring sales. These are heat-tolerant plants, and growing them below 65°F in the greenhouse results in significant delay. Fertility should be at least 150ppm nitrogen, but avoid ammonia in the fertilizer. Plants are best grown at a somewhat higher pH than usual, between 6.4 to 6.8. For best presentation, pinch out the center bud. Side flowers will bloom together, and plants will walk off the shelf. Garden centers […]

Read More

July 30, 2015

Spread Your Risk Beyond Spring Sales [Opinion]

Growers who participated in Greenhouse Grower’s 2015 Spring Crops Recap Survey said they have had enough of the uncertainty that the weather brings. They said it’s time to build up sales in other seasons like fall so we’re not so dependent on spring. As a couple of wholesale growers, both from the Southeast, very eloquently stated, our industry has mastered squeezing everything we can out of the spring season. And while this year happened to be a very successful one, thanks to the improving economy and elevated consumer confidence, they said, “now is no time to celebrate.” “Spring is still Christmas in the horticulture industry, but we have done such a good job focusing on spring that we have neglected other seasons,” one grower said. “Having so many eggs in the spring basket is dangerous. Fall will never be what spring is, but having a solid second season is in […]

Read More
Mike McGroarty, owner of Mike’s Backyard Nursery

July 29, 2015

Backyard Success: Mike McGroarty Educates Aspiring Growers

Mike’s Backyard Nursery sits on a long, narrow, 5-acre property located in Perry, Ohio. There, customers can find a variety of flowering shrubs available, all in 2-quart pots, and all for sale for $5.97 each. Owner Mike McGroarty, a lifelong resident of Perry, says the town has a lot of plant nurseries, including 100 wholesale growers within a 10-mile radius of his house. That doesn’t discourage McGroarty, because he knows that while there are a lot of nurseries in his area, no one else is doing what he is doing. McGroarty has learned about plants — and marketing them to his audience — through decades of experience. He has never hesitated to pass along his knowledge to other growers looking to start their own backyard operations, and has created an entire program to educate aspiring growers. McGroarty Likes To Practice What He Preaches McGroarty’s operation serves as the laboratory for […]

Read More
Latest Stories
WavePetunias-GrowIt_contest_featured

June 18, 2015

Wave Petunias Sponsors Photo Contest Through GrowIt! Ga…

The gardening season is heating up and the Wave Petunias Team wants to see the #WildestWave. The popular plant brand has joined forces with the GrowIt! Garden Socially app to host a two week contest in June that encourages Wave Fans to share and rate photos of their favorite Wave Petunias. The grand prize is a $100 gift card to the garden center of the winner’s choosing. “We are excited to work with GrowIt! and see our Wave Petunias tagged in cities from coast to coast,” says Claire Watson, brand manager for Wave. “Seeing gardeners’ creative photography, awarding a winner, and learning what each region likes about Wave Petunias will be extremely useful as we further promote our ‘Wow ’em With Wave’ ad campaign this season.” Gardeners can place an entry into the contest by downloading GrowIt!, filling out a profile, and uploading photos of Wave Petunias. Placing the tag #WildestWave in the photo’s comments section […]

Read More
Salvia 'Ember's Wish'

March 11, 2015

Annual Salvias – Not Just Red Bedding Plants Anym…

Salvias are popular — and they need not all be the same. Here are a few you know well, and perhaps a few you do not. All are easy to grow and may be found through a broker or grower.

Read More

February 18, 2015

California Spring Trials Sneak Peek: New Annuals For 20…

If you're like us and you can't wait until the 2015 California Spring Trials to see some of the new genetics that will be hitting the market in 2016, never fear. We contacted the breeders who will be displaying their new varieties in California in April, and they gave us a sneak peek. Check out our slideshow to see some of the new annuals making their debut to the trade this spring.

Read More

November 14, 2014

First Vegetatively Propagated All-America Selections (A…

All-America Selections (AAS) honors two vegetatively propagated impatiens with AAS winner status.

Read More

October 13, 2014

Growing Tips For Verbena

Rich Schoellhorn, product manager at Proven Winners, shares some tips for growing verbenas successfully.

Read More

October 13, 2014

Greenhouse Grower 2014 New Varieties Guide: Petunias [S…

Greenhouse Grower asked more than 40 breeders to send photos of new introductions they think are worth your attention. The result is the 2014 New Varieties Guide. See what petunias made the cut.

Read More

June 12, 2014

New Begonia Variety And Coleus Series, Plus Two Lobelia…

Terra Nova Nurseries introduces seven new varieties and one new series.

Read More

May 27, 2014

Two New Salvias Added To Southern Living Plant Collecti…

Two new salvia varieties are now available exclusively to growers from the Southern Living Plant Collection and Sunset Western Garden Collection.

Read More

May 9, 2014

New Petunias Making Their Debut In 2015

Take a look at the new petunia varieties that will be making their appearance in 2015.

Read More

April 23, 2014

Foliage Begonias May Be A Big 2015 Trend [Spring Trials…

A number of breeders debuted their rex begonia and begonia hybrid lines at 2014 Spring Trials.

Read More
Petunia 'Success Violet' from Benary

April 11, 2014

What’s New With Petunias For 2014? [Slideshow]

Breeders are rolling out great new petunia introductions for 2014. Take a look at the variety of petunias they have to offer.

Read More
Verbena 'Superbena Royale Whitecap' from Proven Winners

November 11, 2013

Three New Verbena Superbena Introductions From Proven W…

Three new varieties have joined the verbena Superbena line-up this year: 'Superbena Royale Plum Wine,' 'Superbena Royale Whitecap' and 'Superbena Violet Ice.'

Read More
Calibrachoa 'Mini Famous Double Blue' from Selecta

October 17, 2013

6 New Calibrachoa For 2013

Check out these lovely new introductions in calibrachoa.

Read More

October 10, 2013

Begonia ‘Silhouette Lemon Rose’ Doubles The Bloo…

Begonia ‘Silhouette Lemon Rose’ is a striking begonia hybrid with phenomenal basal and lateral branching. Plant sterility gives maximum continual flowering throughout the season with double the bloom number of a traditional non-stop begonia. Dark mahogany foliage with contrasting emerald green veining provides a dramatic contrast to the soft lemon yellow 1.5- to 2-inch diameter blooms that blush apple blossom pink in high light. This easy-care beauty is ideal for mixed pots and containers, hanging baskets or the summer border. For more information, visit PlantHaven.com

Read More
Petunia 'Flash Mob Bluerific' Burpee Home Gardens

October 7, 2013

18 New Petunias To Add For 2014

Tried and true, petunias are a garden staple. Here are some new introductions breeders are rolling out for your consideration in 2014.  

Read More
Verbena 'Hurricane Hot Pink' from Westflowers

October 7, 2013

New Verbena For 2014

Check out these eight new verbena varieties and consider them for your 2014 greenhouse production.  

Read More
Dahlia Dalaya Shari from Selecta

September 25, 2013

4 New Dahlias For Your 2014 Season

Looking for new dahlia varieties to incorporate in your crop mix? Here are 4 beauties your customers will love.  

Read More
'Wall Street' Coleus from Dummen/Red Fox

September 25, 2013

4 Colorful New Coleus For 2014

Gorgeous foliage makes these new introductions must-haves for next year.  

Read More