Downy Mildew On Impatiens vs. Boxwood Blight

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 offered insight on how the downy mildew on impatiens threat ranks against other disease issues. Kalmowitz also tells us how the current threat to impatiens compares to the new boxwood blight scare.

GG: How does downy mildew on Impatiens walleriana compare to other disease issues you’ve encountered?

KK: It’s a perfect storm when the inoculum appears in the environment and the present climatic conditions allow the disease to move quickly toward devastating an entire planting.

Still, I feel this kind of falls into the more normal range of how a host-specific pathogen can spread so quickly in a species. The reason why there’s such heightened awareness is because it’s such a huge crop. It’s loved from the North to the South. It is a staple of landscape color; it’s always been a prolific flowering plant. It holds up really well and has great form. It has all these attributes, so people have a high regard for it.

GG: How does the new boxwood blight issue compare to downy mildew on impatiens?

KK: Boxwoods are a beloved woody ornamental, just like impatiens are a beloved bedding plant. So there is a heightened awareness of this disease. People are really nervous because they don’t want the disease to spread. If we can keep it to the areas where it was already found, it would be better. I don’t think we know enough about boxwood blight [as of late February]. We don’t know how it becomes established in a boxwood planting. Does it infect a mature boxwood as much as one in a production stage?

I know it does move across all boxwoods. Unlike impatiens and the walleriana species, this disease moves from Japanese to American to English [boxwoods]. And that means if you get boxwood blight in your nursery or in your landscape, then you have to switch out of all boxwoods.

GG: What do we know about existing products and their ability to combat boxwood blight?

KK: Our product Pageant fungicide is extremely broad. It has two active ingredients that work together in order to have activity on the target. We have cylindrocladium on our label. It was in the English trial and, thus, there is some precedence to using our product.

[North Carolina State University Associate Professor and Extension Specialist] Kelly Ivors has been asked to do a containment trial. We all look forward to her work this spring. She has been asked to do her trial in a more isolated area of the research station so boxwoods can be contained and not exposed to production areas that have a lot of woody plant production.

Leave a Reply

One comment on “Downy Mildew On Impatiens vs. Boxwood Blight

  1. It's worth pointing out that downy is spread by wind and boxwood blight isn't, so a planting of Impatiens walleriana is more likely to be infected than a planting of boxwood as long as you're careful about where your box come from and take regular, common sense protection measures. Also, while it's true that boxwood blight is thought to infect all boxwood (it hasn't been tested on every cultivar yet), it's incorrect to assume that getting boxwood blight in your nursery or landscape means you "have to switch out of all boxwoods". Many European gardens have had boxwood blight on their grounds for years and still have healthy plantings. If conditions aren't right, there's no blight. We saw a hedge at Wisley that had a blighted plant removed and the adjacent plants are perfectly fine.

More From Annuals...
Sedum-Pillow-Talk

February 20, 2018

12 New Poinsettias and Succulents for Holiday Sales, Crafting, and Landscaping

Poinsettias and succulents are both in-demand products with today’s consumers. Here’s a look at some of the newer introductions available for retail sales in 2018 and 2019.

Read More
Pepper-Mexican-Sunset

February 19, 2018

All-America Selections Names Latest Variety Winner, Announces New Display Gardens and Judges

All-America Selections (AAS), the 85-year-young non-profit plant trialing organization, had a very busy month of January.

Read More

February 6, 2018

20 Trends That Dominated at TPIE

If you're looking to stay on top of the current trends to stay ahead of the competition and increase value to your clients by helping them stay at the forefront of their industry, check out some of the new products and ideas we saw trending at TPIE this year.

Read More
Latest Stories

January 4, 2018

Stand-Out New Varieties That Keep D.S. Cole Growers Co…

See what new varieties stood out to Doug Cole, owner of D.S. Cole Growers in Loudon, NH, this year.

Read More
Begonias-I’Conia-Series-Dümmen-Orange-Miss-Montreal

December 19, 2017

34 New Flowering Annuals to Brighten Up Your Product Mi…

Consumers will soon have the opportunity to experiment with colorful, big-impact blooms in their containers and landscapes. Here are 31 new introductions to consider that will color-up your product mix.

Read More
Eason-New-Calibrachoa-Hi-Graft

November 14, 2017

Eason Horticultural Resources Introduces New Decorative…

Created by Hishtil Nursery in Israel, the new decorative forms of calibrachoa feature an 8- to 12-inch stem and come in four colors of calibrachoa blooms on top.

Read More
Helianthus Sunfinity (Syngenta Flowers)

September 3, 2017

Growing Tips for Helianthus Sunflower ‘Sunfinity…

This annual sunflower is a profuse bloomer with strong branching that produces multiple flowers per plant from spring to fall.

Read More

August 29, 2017

27 New Impatiens for Spring Color in 2018

Gardeners love impatiens because they are one of the few plants that offer stand-out, splashy blooms for shady areas, and in some cases full sun. There's no shortage of new introductions this year to choose from for your 2018 product mix. Here are 27 new and improved varieties to consider offering to your customers.  

Read More
Candy Tops Snapdragons Series (Sakata Ornamentals)

August 3, 2017

Five Characteristics Breeders Want in Top-Performing Sp…

New spring annuals have to provide something for everyone — longevity, durability, performance, and more — if they want to meet breeders’ high standards for market-worthy plants.

Read More
Petunia 'Headliner Pink Sky" (Selecta)

August 3, 2017

Why Eccentricity is the New Black in Spring Annuals

Consumers judge plants by appearance, color impact, and ease of maintenance, which is why retailers want new spring annuals that are novel standouts.    

Read More
Petunia 'Amore Mio' (Danziger)

June 8, 2017

AmericanHort Update on Genetically Engineered Petunias

AmericanHort is actively assisting affected plant breeders, distributors, growers, and retailers as the genetically modified petunia regulatory response continues. Since the last update, there have been several changes to the list of petunias confirmed or suspected of being genetically engineered and therefore unauthorized to be imported or sold. Also, the list of recognized laboratories for petunia variety confirmation testing has expanded. Most importantly, petunia varieties on the USDA-APHIS Biotechnology Regulatory Services (BRS) list require an APHIS Form 2000 for importation. APHIS also began requiring that any Petunia spp. Shipments, not including regulated GE varieties, must be accompanied by a list of variety names. This resulted in some inspection delays at the USDA-APHIS plant inspection station in Atlanta over the past two weeks. In response, AmericanHort has negotiated a more flexible approach with APHIS, and new guidance has just been posted for importing Petunia plants, cuttings, or seed. The new guidance allows […]

Read More

May 25, 2017

Genetically Modified Petunia Update: Breeders Take Swif…

Now that the initial shock of genetically engineered petunias is wearing off, breeders continue testing for tainted stock and look toward the future. On the consumer side, uncertainties remain.  

Read More

May 23, 2017

USDA-APHIS Bulletin on Unauthorized Distribution of Gen…

On May 2, 2017, USDA-APHIS was informed that an orange petunia variety was potentially genetically engineered and had been imported and moved interstate without required authorization by APHIS. This led to testing of numerous petunia varieties, which confirmed this particular variety and several others are genetically engineered, and meet the regulatory definition of a regulated article under APHIS regulations. APHIS continues to work with the industry to ensure unauthorized GE petunias are not distributed in the United States.

Read More
Petunia F1 African Sunset from American Takii

May 22, 2017

Genetically Modified Petunia Update: Question and Answe…

AmericanHort’s key role interfacing with the USDA on the recall of genetically modified petunias has helped the horticulture industry rapidly address the problem. Senior Vice President Craig Regelbrugge talks about recent updates, the impact on the industry, and where it goes from here.

Read More

April 25, 2017

41 New Vegetative Petunias From California Spring Trial…

With the abundance of new introductions for the 2018 retail season, we’ve made it easier for you to sift through them by separating out the vegetative petunias from the Northern sites, which includes selections from Westhoff Flowers, Sakata Ornamentals, Danziger, Proven Winners, and Syngenta flowers.

Read More
Zinnia Solmar Series (Floranova)

March 17, 2017

Phlox, Zinnias, and More for 2018 From California Sprin…

We asked breeders to share with us pictures and information on some of the great new annuals that you'll see at California Spring Trials 2017. They didn't let you down.

Read More
Cosmos ‘Apollo’ (Floranova)

March 14, 2017

Begonias, Dahlias, and More for 2018 from California Sp…

We asked breeders to share with us pictures and information on some of the great new annuals that you'll see at California Spring Trials 2017. They didn't let you down.

Read More
Limbo GP burgundy picotee

March 7, 2017

New Petunias and Calibrachoas for 2018 from California …

We asked breeders to share with us pictures and information on some of the great new petunias and calibrachoas that you'll see at California Spring Trials 2017. They didn't let you down.

Read More
Sea Breeze Catharanthus combo

December 2, 2016

Four Mixed Container Trends To Watch

Mixed containers are still one of the best-selling SKUs at retail. Pay attention to these four trends that are making their mark on multi-liner mixes and combination containers.

Read More

September 7, 2016

Check Out The Best Annuals For Attracting Bees And Butt…

Public interest in protecting bees and other pollinators has initiated a new market for flowers that are good food plants for pollinators. Here's a list of annuals Michigan State University Extension recommends that are attractive to bees and other pollinators.

Read More

September 6, 2016

10 Colorful Spring Plants For Sales In 2017

Trends with plants come and go, but color always sells. These spring crops for 2017 offer color choices ranging from bold and vibrant hues to understated, softer tones, and they’re versatile enough to be used in baskets, containers, beds, and borders.

Read More