A Newsletter for Professionals Growing Greenhouse Crops in the Rocky Mountain Region

Contents

• Are Plant Pathogens in Your Irrigation Water
• New Greenhouse Construction at CSU
• BPI 2000 in Vancouver
• Rocky Mountain Greenhouse Short Course

Are Plant Pathogens in Your Irrigation Water?

The answer to this question involves answering why a plant disease problem occurs in a greenhouse, so it often becomes complex. Plant pathogens can be introduced into a production system in many ways, only one of which is water. Air, soil (potting soil, soil under benches or in used pots or other containers), insects, mites and other animals, and cuttings or plugs that are already infected when purchased are all viable ways for pathogens to enter. This must be kept in mind when trying to solve a plant disease problem in the greenhouse.

Only a few pathogens, of the many known to cause crop loss, such as tobacco mosaic virus, Erwinia, Fusarium, Pythium, Phytophthora, and nematodes have been traced to being introduced in water. Pythium is by far the organism most commonly encountered of this group. Not only can it be found in water, but in soil, sand and peat, and it can also be moved from place to place by fungus gnats and shore flies.

Another factor to consider in this complex question of what is in irrigation water, is what type of irrigation system is being used. The majority of concern regarding pathogens in water is in recirculated systems such as ebb-and - flow and flood floors rather than traditional open irrigation systems.

In 1993, Karen Panter and I looked at whether irrigation water in Colorado greenhouses might be a source of Pythium and Phythophthora spp. (HortTechnology 7(2):153-155). Greenhouses using municipal water, well water, and surface water (holding ponds) took part in the survey. We found, in the water sources we tested that no pathogens could be detected in municipal or well water sources. Once water was held for a prolonged period of time in a holding pond, then certain species of Pythium were detected. (We found P. dissotocum and P. rostratum, both of which turned out to be weak pathogens in subsequent testing).

The study that Karen and I did, plus research and information coming out from around the United States would suggest that, yes water can be a way that pathogens are disseminated. Perhaps, though, it is most important that we take a look at the whole system and find out what other factors are also involved. For example, if Pythium is indeed a problem in your operation, and you know it is in the recirculated water-how did it get there? It would appear that municipal and well water sources are free of plant pathogens in Colorado. If you are using those water sources, what happens to the water after it enters your greenhouse? It is coming in contact with soil, plant debris or previously infected plant parts?

The bottom line is to make sure production areas are as clean as possible and production practices don't enhance certain problems. While you can't prevent every disease, many can certainly be avoided with small changes. Gary Moorman from Penn State said this best last year at the 1999 Rocky Mountain Greenhouse Short Course. "Regardless of whether the incoming water contains the pathogen or the reservoir has become contaminated from another source, major disease outbreaks occur when watering times are longer and when benches are not draining thoroughly. If watering times are not excessive, the net flow of moisture is upward into the potting mix and there is little time for pathogens to move out of potting mix, onto the bench, and into the reservoir or to neighboring plants."

If Pythium is a problem in your greenhouse recirculating irrigation system, Dr. Moorman suggests the following:

1. Keep flood times as short as feasible
2. Monitor soluble salts and keep them as low as feasible
3. Consider putting a fungicide or biological control agent in the potting mix at transplant. NOT IN THE WATER. Fungicides can not be put in the water because they are not labeled for this use and it makes the entire contents of the reservoir a hazardous material subject to disposal regulations.

No endorsement of products mentioned is intended nor is criticism implied of products not mentioned. As always, before using any pesticide, consult the label.

Laura Pottoff
Extension Pathology Agent
Jefferson County

New Greenhouse Construction at CSU

Probably some of the best news that we can report from Colorado State University is the construction of new greenhouses. On the site of the University Greenhouses on the main Colorado State campus, the old glass houses have been razed and new greenhouses are being erected.

In late July demolition began and at the date of this release, concrete is being poured for the floors.

Former University Greenhouse	Old Foundation	Grading Site
Removal of debris	Rough grade	Final grade
Setting foundations	Foundation trench	Foundation forms
Foundation construction	All photographs courtesy of J. Tom Smith Plant Facilities Manager

A few of the amenities that are being installed are as follows:

• Gutter connect Nexus Vail ranges
• Hot water heated floors
• Wadsworth EnviroSTEP control technology
• Horizontal Air Flow Fans

Greenhouse floor	Hot water heat manifold	Greenhouse floor with heat tubing
Pumping concrete to floor	Forming the floor	Finished Floor
All photographs courtesy of John Ray Horticulture and Landscape Architecture

This project represents years of planning and negotiations with many players involved. However, most of the successes must be directed towards our Plant Growth Facilities Management, J. Tom Smith, who has guided the project to this level.

For more information and updates, contact Tom Smith.

Steven E. Newman, Ph.D.
Greenhouse Crops Extension Specialist
Horticulture and Landscape Architecture

BPI in Vancouver

The Rocky Mountain Region of the United States was well represented at the recent Bedding Plants International Conference in Vancouver, British Columbia. Three of us from Wyoming (Charles and Lynn Sprout from Sprout's Greenhouse in Lander and yours truly) plus quite a few from Colorado -- well, let's just say they knew we were there! Steve Echter, Mike and Flo Novovesky, Natalie Miller, Brian Yantorno, Steve Flickinger, Jeff Warschauer, Mitch McDonald, Paul and Paula Yantorno...hope I didn't forget anyone ...all made the trip. We are quite proud of our new BPI President, Paul Yantorno, and are confident that his next year in office will prove an exciting and productive one for BPI and its members.

Butchart Gardens

The conference itself was outstanding, rivaling the BPI conference we hosted in Denver in 1998. Tours took 2-1/2 days of the conference and all of them received rave reviews. It seems as if every greenhouse business in the Pacific Northwest has a retractable roof greenhouse. The crops grown under these roofs vary tremendously from poinsettias to perennials to vegetable transplants. And yes, they will work in the Rocky Mountain Region too. The educational sessions were all very well attended and provided new insights into bedding plant production for the years to come. There were other activities, too, including receptions, Fun Night, and the Landscaping with Color contest.

Retractable roof section at Burnaby Lake Greenhouses in British Columbia

During the annual business meeting, our own Mike and Flo Novovesky were awarded lifetime memberships in BPI, rewards for their contributions and dedication to our industry. The Futura Award went to Margery Daughtrey, of Cornell University, for her work over the years in educating growers about diseases affecting greenhouse crops and ways to manage them effectively (Steve Newman won this award last year). There were many other awards, all of them quite deserving. For those of us who attended the conference, we came away with a greater understanding and appreciation of our Canadian partners. Vancouver is a fabulous city in one of the most beautiful settings you'll find anywhere. We were given the Red Carpet treatment by all of our hosts, especially those whose greenhouse operations we had the opportunity to visit. We enjoyed terrific hospitality, renewed old acquaintances, and made many new industry friends to boot.

Next year's conference? Late September 2001 in Baltimore, Maryland.

Greenhouses at Valleybrook Gardens in Abbotsford, British Columbia. Mount Baker is in the background, which is in Washington state.

Karen L. Panter
Horticulture Extension Specialist
University of Wyoming

Colorado State University Cooperative Extension and the Colorado Greenhouse Growers Association is pleased to announce the 2000 Annual Rocky Mountain Greenhouse Short Course.

October 18-19, 2000 at the
Arvada Center for Arts and Humanities
6901 Wadsworth Blvd., Arvada, Colorado

The topic for the program this year is Understanding Greenhouse Nutrition and Media Technology. We have four top speakers who will be providing the material. Contact Bob Briggs at the CGGA Office for more information or download the brochure by clicking on the link below.

Download the Brochure
requires Acrobat Reader

Plan to attend the CGGA 75th Anniversary Gala
Wednesday 18 October, 2000
Keynote speaker will be Paul Ecke, III
Paul Ecke Ranch

Contact the CGGA Office for details

Steven E. Newman, Ph.D.
Greenhouse Crops Extension Specialist
Horticulture and Landscape Architecture