Using Dead Diseases to Make Stronger Cut Flowers?

Here is a new term for you to learn – Plant Health Regulators. What are plant health regulators and what can they do for you? Good question and we at the University of Maryland Cooperative Extension are going to set out to find some answers for cut flower growers in 2004.
This winter we were approached by Paul Bystrak of Eden Bioscience asking us to work with their company in testing out this new classification of material called “Plant Health Regulators (PHR).” Paul explained that their company had a PHR product called a harpin protein that they market under the trade name “Messenger.”

Want to Stimulate Your Cut Flowers – Cheap?

The harpin protein is identical to a naturally occurring protein produced by the plant pathogen Erwinina amylovora (fireblight). When sprayed onto the foliage and stems of a plant, plant receptors recognize the protein’s presence and send a signal throughout the plant. Hence, you got a stimulated plant.
How does it do this? Good question! The harpin protein activates several internal biochemical responses from the plant that enhance plant growth  in some cases, and supposedly increases insect and disease resistance. The Eden Bioscience company literature says it stimulates the salicylic acid dependent pathway, the jasmonic acid induced pathway (involved in plant defense) and plant growth systems, including enhanced nutrient uptake and increased net photosynthesis. Eden Bioscience says this harpin protein increases photosynthesis, increases nutrient uptake, increases biomass, improves root development, results in earlier flowering, and with fruit crops improved yield and size.
Messenger is being used on cherry crops in the Midwest, strawberry plants in California, and on grapes in California.. In each of these fruits the crop yields have been increased or quality of the fruit increased. Field trials are being conducted with harpin protein on grapes in Maryland. Even the tobacco industry is trying out harpin proteins to improve leaf thickness in tobacco plants.
Work on harpin proteins had been conducted at Cornell University by Dr. Zhongmin Wei and his colleagues and published in the July 1992 issue of Science Magazine (Volume 257). Eden Bioscience of Bothell, Washington had developed a way to manufacture and market this product. Work at Cornell University had shown that harpin proteins trigger mechanisms for plant growth and protection. The federal EPA has labeled Messenger as a toxicity category IV product which is a designation reserved for materials with the lowest hazard potential. It has a 4-hour REI. Eden is pursuing certification for Messenger as a product for use on organic food crops.

Can a Harpin Protein do Anything for Cut Flower Crops?

Good question and the University of Maryland Cooperative Extension made a first attempt at quantifying whether harpin proteins would have a positive impact on flowering plants. We recruited Catoctin Greenhouse, owned by Bob Van Windergen, of Detour, Maryland. Bob agreed to work with us on a field trial and turned us over to his able- bodied head grower, Henry Thorpe and associate grower, Julie Weiland  We asked the growers at Catoctin greenhouse to choose four annual bedding plant species or cultivars that had problems with insect or disease. We asked them to further divide this into two species that tolerated drought and two that were somewhat drought tolerant. Between the growers, the researchers, and the Eden bioscience technical representative, Paul Bystrak, we selected a plumed celosia variety and vinca – the drought tolerant species. The other two species selected for the study were petunia and ageratum.
Results of Greenhouse Trial – Phase I

Annual vinca treated with Messenger showed the most noticeable response. Treated plants that received treatment in the plug and two treatments of plug stage and 2 weeks later showed greater vigor in root growth and top plant growth compared to untreated control plants. The number of blooms was also increased.
In another greenhouse range, during the time the trial was conducted, the grower experienced heavy loss of several thousand vinca plants damaged by Pythium root rot.

Where Do We go From Here?

In 2004 we plan to test Messenger and another harpin protein product on a couple of cut flower plant species. The ASCFG has been generous in supporting this field research project. Eden BioScience has agreed to match the ASCFG funding for this trial. We have asked David Dowling to work with us in a growers trial evaluation. We will also conduct replicated trials at the Central Maryland Research and Education Center in 2004. We will evaluate harpin protein product to see if they enhance plant growth, measured by plant height, shape, quality, and bloom time occurrence. We will also evaluate whether the harpin proteins influence damage levels from insect and disease organisms.