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

Contents

• Systemically-Acquired Resistance
• Tospoviruses in Bedding Plants
• News from the Lab
• Fertilizer Calculations: Understanding Parts per Million
• Chemical Storage in Greenhouse

Systemically-Acquired Resistance

Will theoretical research become reality for growers? Anyone who has spent a significant amount of time investigating disease-prevention options has certainly encountered the phrase, "Systemically-Acquired Resistance" (SAR). This is an exciting area of research that focuses on a pro-active approach to enhance the health of the plant for disease prevention, instead of reacting to diseases with treatments (if available), after infection occurs. SAR is basically utilizing substances that activate the plant's own immune response. This can be thought of as a type of inoculation that is used to strengthen the plant's ability to defend itself against diseases. A major advantage of SAR is that it can provide systemic disease resistance against a great variety of pathogens.

A new product may make SAR a viable option for growers in their efforts to prevent disease in the field and in the greenhouse. Eden Bioscience in Bothell, Washington has been working with researchers at Cornell to develop a product known as "Messenger". The product is reputed to have several major benefits to crops including increased growth, disease resistance and ability to repel pests. The researchers based their studies on the belief that plants have a great innate ability to prevent diseases and insect infestations. They only need a signal to turn on that resistance.

The active ingredient of Messenger is a naturally occurring protein called harpin. This protein is a component of the bacteria that causes the disease known as fire blight. Zhong-Min Wei, who is now vice president of research at Eden Bioscience led the research team at Cornell that discovered harpin in the 1990's. The scientists discovered that the protein serves to activate plants' auto immune responses. This reaction usually occurs within five minutes, with a full response in three to seven days. In nature, bacterial infection triggers the immune response. By isolating the harpin protein, the plant's immune system can be strengthened without introducing a pathogen. Of course, this is no magic bullet. It does not cure plant diseases, nor does it kill insects. However, it does seem to enhance the plant's ability to protect itself from infection while stimulating growth. Basically, the product sends a message to the plant to protect itself.

This product has undergone extensive testing in thousands of greenhouse studies and more than 500 field trials on over 45 crops in the United States, China and Mexico. The field trials were conducted in scientifically designed, randomized small plot studies as well as from large-scale trials ranging in size from one to 80 acres. In these studies, Messenger was proven effective on a broad spectrum of crops such as tomato, pepper, cucumber, roses and strawberries. In China, field trials demonstrated yield increases of 30 to 40%. In the US, with crop protection strategies that are more sophisticated, yield increases of 15 to 20% were observed in several trials, according to Eden Bioscience.

The research results demonstrated the product's ability to activate a plant's natural defense system, resulting in resistance against a variety of viral, fungal and bacterial diseases. In a field trial in New Mexico, Messenger had a reduction in beet curly-top virus symptoms of 48 to 58% compared with non-treated control plots. As expected, a decrease in symptoms was strongly correlated with an increase in yields. In tomatoes, field studies showed an increased germination rate, increased plant growth, quicker fruit maturation, increased yield, and a greater percentage of fruit graded as extra large. The product was shown to prevent Fusarium wilt, Tobacco Mosaic Virus, Cucumber Mosaic Virus, Bacterial leaf spot and Bacterial Wilt (yes, Ralstonia solanacearum)! In addition, the plants had lower infestation rates for Armyworms, Aphids and Thrips. Impressive disease prevention results were demonstrated in a wide variety of crops.

Messenger is composed of 3% harpin protein and 97% food-grade products. A major difference between this product and conventional chemical sprays is that entire plant coverage is not necessary for the product to be effective. Actually, only a small portion of each plant needs to be sprayed. Two grams of the product (one-teaspoon) is all that is needed to treat one acre. Messenger may be applied as a foliar spray or through irrigation systems. It may also be used as a seed treatment or drench. The product leaves no detectable residue on crops or in water, and the harpin protein disintegrates shortly after the application. The product is supposedly non-phytotoxic. It is quite safe for humans and the environment as well. The EPA classifies this as a Toxicity Category IV product, which is reserved for the safest materials. It is virtually nontoxic to birds, honeybees and aquatic organisms. It is also compatible with biological control agents, also known as beneficial insects. Due to the product's lack of toxicity and residue, it can be applied with a minimum of personal protective equipment (PPE) and qualifies for the EPA minimum four-hour reentry interval requirement (REI).

While press releases from the manufacturer are quite optimistic, growers who tested the product give the best testimonials. Dr. Larry Beasly, Vice President for Corporate Services at A. Duda and Sons, Inc., one of the larger vegetable growers in the country stated,

"In research trials performed by A. Duda and Sons in citrus, an untreated check of the fruit had 85% scab infestation. Two applications of Messenger during the flush reduced this infestation to less than 5%. By comparison, when copper was applied ever other week as a grower standard practice, the infestation was reduced to only 7%."

Austin Stem at A&S Farms in Immokalee, FL says,

"This past fall, we cooperated in the Messenger EUP program on tomatoes. We were able to significantly reduce our total fungicide program by using Messenger and picked 4.3 bins more tomatoes per acre than in the non-Messenger-treated fields.

" Wayne Heller at Lipman & Lipman Farms in Duette, FL gives this testimonial,

"A product like Messenger fits into our tomato IPM program perfectly. We can reduce our fungicide use, especially copper, and see an increase in plant health and final yields without sacrificing disease control. We see Messenger as a potentially important tool for managing a healthy and profitable tomato crop."

If the product has a reasonable price, it may be a good option for US growers. It has the potential to reduce the need for other chemical-based crop treatments, which can decrease the overall cost of production. After field trials, the initial response of growers is positive. However, it is ultimately the growers who will decide the ultimate value of Messenger, after they determine for themselves the benefit it holds, if any, for their crop production systems.

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

Chris Freeman
Area Specialist Commercial Greenhouse
Adams County

Tospoviruses in Bedding Plants

Spring time brings warmer weather, lots of garden activity and virus diseases. Tomato spotted wilt (TSWV) and impatiens necrotic spot (INSV),Tospoviruses, are the most common diseases caused by viruses found in Colorado Greenhouses. In turn plants with these diseases are accidentally moved into the Garden Centers and then distributed into landscapes. Viruses are often difficult to diagnose, have a potential for extreme crop value loss, and are even more difficult to eradicate. Symptoms of these viruses vary depending on the plant affected and type of virus. To date there are over 500 known hosts of TSWV and INSV.

Plants commonly affected in Colorado include:

Symptoms range from stunting, necrotic leaf spots, chlorotic leaf spots, areas of black or brown stem necrosis, ring spots, mosaic, line patterns, and vein necrosis. Management of these viruses are dependent upon elimination of infected plants, making sure they don't reach the landscape and control of thrips, the vector of the disease. For more information, see CSU Extension Fact Sheet on Greenhouse Plant Viruses (TSWV/INSV): 2.947

Downy mildew alert! Downy mildew continues to be causing problems this spring in snapdragons, salvia, roses and other cut flower operations. Cool temperatures and high relative humidity favor this disease. Remove symptomatic plants and be sure to avoid plant debris on the soil surface. Debris and weeds will harbor the fungus. Fungicides labeled for control include mancozeb, fosetyl Al, and metalaxyl.

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

News from the Lab

The plant hormone auxin

Unlike ethylene, auxins represent a class of hormones. The most common auxin is IAA (indole-3-acetic acid), but other auxins include IBA (indole-3-butyric acid) and 4-Cl-IAA (4-chloroindole-3-acetic acid). Compounds are classified as auxins based on their biological activity in plants. One of these activities includes cell elongation and stimulation of growth. Auxins were studied as early as the late 1800s by Charles Darwin. Darwin noticed that grass coleoptiles would grow toward a unidirectional light source. He found that while the coleoptile tips perceived the light stimulus the growth response of bending toward the light was in the growth zone several mm below the tip. He concluded that a chemical messenger was transported from the site of perception to the response zone and this chemical was later identified as the first plant hormone, auxin. Because the substance promoted elongation of the coleoptile it was named auxin from the Greek work auxein " to increase" or "to grow". Many synthetic auxins like 2,4-D (2,4-Dichlorophenoxyacetic acid) are used as herbicides to control broad leaf weeds. These synthetic compounds are called auxins because they biological activity like IAA. While they are auxins they are not classified as plant hormones because they are not synthesized by the plant. This class of auxins are therefore referred to as growth regulators rather than plant hormones.

Auxin stimulates ethylene production:

Since auxin was the first plant hormone to be discovered it was long thought that all growth and developmental processes were controlled by auxin, and that there were no other hormones. For example, many of the effects of ethylene described in last months article were originally attributed to auxin. This is because the application of auxin to plant tissues stimulates ethylene production from that tissue. You can therefore see the difficulty in determining which plant hormone was the primary stimulus of the response. Only recently has the role of auxin in adventitious rooting come into question. Research by a group in Florida has investigated the role of ethylene in adventitious root formation on petunia and tomato cuttings. Using plants that had been genetically engineered to be insensitive to ethylene they can determine if adventitious root formation is stimulated by ethylene or auxin. They found that rooting in these cuttings was dramatically reduced. Even when treated with auxin (rooting compound) the numbers of roots did not substantially increase. They conclude that when normal wild type cuttings (from plants that have normal sensitivity to ethylene) are treated with rooting compound it is the ethylene production stimulated by the auxin application that is really controlling rooting.

Ethylene controls adventitious rooting Photo courtesy of Dr. David Clark, University of Florida

Many hormone responses are due to interactions between multiple hormones:

A number of aspects of plant growth and development are also influenced by the ratios of multiple hormones present in a tissue rather than the concentration of one particular hormone. An example of this can be seen in tissue culture. When the ratio of auxin to cytokinins (CK) is high callus tissue will differentiate into roots. When auxin to cytokinin levels are low (or cytokinin levels are higher) callus forms shoots.

High auxin, low CK roots Low auxin, high CK shoots Intermediate levels of CK and Auxin undifferentiated callus

Auxin effects on plant growth and development include:

1. Stimulation of stem elongation
2. Inhibition or stimulation of root elongation depending on the concentration. (Very low concentrations of auxin can stimulate root elongation, but levels that stimulate stem elongation are inhibitory to root elongation).
3. Abscission of leaves on intact plants and cuttings (due to increasing ethylene).
4. Adventitious root formation
5. Increased apical dominance
6. Decreased lateral branching

What are the practical applications of auxins in horticulture?

1. Rooting of cuttings - auxin in rooting compound (usually IBA) stimulates adventitious root formation
2. n tissue culture auxins stimulate the formation of roots
3. Synthetic auxins like 2,4-D are used as herbicides
4. Stimulation of fruit set in unpollinated ovaries of solanceous plants
5. Chemical thinning of apple and pear fruits

Michelle L. Jones, Ph.D.
Assistant Professor of Floriculture
Horticulture and Landscape Architecture

Liquid feed fertilizer programs used in greenhouse crop production allows a grower to manipulate plant nutrition conveniently. This is done by using different fertilizers containing equal ratios of nutrients and adjustment of specific fertilizer elements within a fertilization program. These ratios are calculated using the formulas discussed in the previous issue.

To apply soluble fertilizer to a crop in its final dilution, fertilizer injectors are used to introduce the fertilizer into the irrigation water. There are two major categories of injectors: proportional fertilizer injectors and positive displacement fertilizer pumps (non-proportioning types).

Proportional fertilizer injectors

Differential pressure injection may be accomplished by a pressure differential such that the pressure of the point of injection is less than at the intake of concentrated fertilizer. Concentrated fertilizer is then pulled into the irrigation water. This is accomplished by connecting a hose to the vacuum side of the irrigation pump and placing the other end in the concentrated fertilizer solution. An adjustable valve in the hose or a series of valves are used of control the volume of concentrated fertilizer solution withdrawn. This is done to vary the fertilizer concentration without modifying the concentrate. The injected fertilizer concentration can inadvertently be altered by changes in pump speed and line pressure due to leaks, clogged nozzles, and faulty valves- If air is allowed to enter the stock fertilizer suction line, the system will probably have to be reprimed.

Venturi type proportioners are similar in principle to the system described above. As water flows through a constriction in the proportioner, the water speed increases and pressure decreases. A tub attached at the constriction facilitates movement of fertilizer from the concentrated solution into the irrigation water. The Siphon Mixer uses the venturi principle and has a dilution ratio of about 1:15 with inlet water pressure of 30 psi. Changes in inlet water pressure, flow rate, or any factor creating back pressure on the output side of the proportioner such as a constrictive nozzle or a kink in the hose, will alter the dilution ratio. Generally, 50 feet or less of hose is used although some line pressure drop is experienced regardless of hose length. The Siphon Mixer has a dilution capacity of one gallon of concentrate in five minutes.

Displacing concentrated fertilizer dilution into the irrigation water is another example of pressure differential injection. There is a bag inside a metal tank. As water fills the tank, the bag (containing fertilizer concentrate) collapses forcing fertilizer concentrate into the irrigation water. This type of injector contains few moving parts; however, inlet water pressure and flow rate does alter injection accuracy. Flow control valves are used to compensate for variations in inlet flow rate.

Water motor controlled injectors use water flow to operate a piston or diaphragm that injects or forces fertilizer into the irrigation water by positive displacement. As water flows through the injector, the water moves a cam to turn and push a piston back and forth. Consequently, oscillation of the piston varies with water flow.

Water meter controlled injectors use a water meter mechanism to determine the flow rate and water powered diaphragm pumps to inject the fertilizer.

Positive displacement fertilizer pumps displace a fixed amount of concentrated fertilizer each time fertilizer is forced into the irrigation water. A piston or piston and diaphragm is used to displace the fertilizer. Injectors of this type are usually driven electrically and should have a common electrical circuit with the irrigation water pump so the injector will stop when the irrigation pump is stopped.

When positive displacement injectors are use, a blend-tank may be needed in the water line immediately following the point of injection to ensure adequate mixing of water and fertilizer. This is especially true if the fertilizer passes thorough pipe lengths insufficient to adequately mix the fertilizer.

Injection Calculations

After selecting an injection system for proportioning concentrated fertilizer into irrigation water the amount of fertilizer to be dissolved into the concentrate must be calculated. Regardless of the type of proportioner or ratio, the first step of determining the amount of fertilizer is to determine the volume of irrigation water to be applied. To do this, note the proportioner rate given by the manufacturer. These values are given as a ratio, for instance 1:100. What this means is that for each 100 units of water, 1 unit of concentrate is mixed for a total volume of 100 units. Therefore, 50 units of concentrate will yield 5,000 units of fertilizer and irrigation water. Note that "units" can be changed to gallons, liters, quarts, or any other volume to suit your needs.

After the total volume has been calculated, all that is left to determine is the amount of fertilizer to mix a concentrated solution. Take the value 8.09 oz. ammonium nitrate / 100 gal. of water which yields 200 ppm N calculated in Part 1, and simply multiply by 5,000. This results in the value 404.5 oz. or 25.3 pounds of ammonium nitrate that must be dissolved in 50 gallons of water using a 1:100 proportioner.

When mixing concentrated fertilizer salts in water, remember to use hot water. As salt dissolves in water, an endothermic reaction occurs. This means that heat is removed and the water chills. This is the same reaction used to chill ice cream in a hand crank freezer. Therefore, if hot water is not used, the fertilizer concentrate may chill to a temperature too low for adequate blending.

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

Greenhouses use a wide range of chemicals, sometimes in large quantities.  These chemicals have to be stored properly to ensure workers are not injured and there is no environmental contamination.  Normally I focus my efforts on protecting humans from injury.  For purposes of this article, I located information provided by the EPA on their web sites:

http://www.epa.gov/grtlakes/seahome/fert/src/main.htm http://www.epa.gov/grtlakes/seahome/pest/src/main.htm

There are several factors to take note of when looking at the “Small-Scale Fertilizer/Pesticide Storage Facility” diagram included on the EPA’s web page:

• Exhaust fan to outside.  When installing the exhaust fan be sure it is vented to the outside of the greenhouse.  In addition, verify that no building air intakes are near the fan exhaust, which can lead to contaminated air being drawn back into the building.
• Liquid and dry chemicals are stored on separate shelves, liquids along one wall, dry chemicals along a different wall.
• A sump pump is located in the floor to drain chemical spills and water from the eyewash (presumably to a holding tank or water treatment system).
• Outlets with ground fault circuit interrupters (GFCI’s).  These electrical outlets typically cost $10 each, or less, and protect workers from electric shock.  They are especially useful in areas where there may be liquids that can come in contact with electrical devices.
• Eyewash.  Many facilities have installed portable eyewash stations in their chemical storage areas.  Keep in mind that most chemical labels have a recommendation that the injured person flush their eyes with fresh water for at least 15 minutes after being exposed to a chemical.  A one or two liter bottle of water is not going to accomplish that.  There should be a clear path to the eyewash, which means not placing obstructions (boxes and containers) in front of it.
• Smoke alarm.  Typically installed in the center of the storage area on the ceiling.  If your facility has a hardwired fire alarm system, tie this smoke detector into that system.
• Fire extinguisher(s).  It is desirable to install a fire extinguisher on the wall near each exit to the storage area.  The idea is not that the employee will fight a chemical fire.  Fire extinguishers should only be used by workers who are trying to escape from a fire.  Workers who are asked to fight a fire as part of their job requirements must receive special training.  All workers should be trained on the proper use of fire extinguishers.

From a safety standpoint, there are additional issues to consider with chemical storage:

• Labeling.  All chemicals should have the original manufacturer label on them.  This label includes important information such as first aid procedures, emergency phone numbers, dangerous reactions that occur when mixed, proper use and disposal.  If a chemical is transferred to a secondary container, that container should ideally contain a label with all the pertinent manufacturer information.
• Storage area should be locked from the outside.  This will ensure that only workers who are trained to use the chemicals have access.
• Incompatible materials should be stored separately.  The label will specify what chemicals a certain product should not be stored near.
• Lighting.  Storage area should be well lit so workers can easily read labels and readily identify leaking containers.
• Temperature.  Maintain the temperature in the storage area at, or below, the level specified on the chemicals’ labels.
• Report spills promptly so that they can be cleaned up right away.  Clean up should be performed by employees who have training on the hazards involved and know how to wear the personal protective equipment that is called for by the chemical’s label.
• No Smoking!  Clearly post “NO SMOKING” signs in areas where chemicals are stored and handled.  Even if the chemical is not flammable, a worker can be exposed when they smoke if they don’t wash their hands thoroughly.  Eating and drinking should also be prohibited in these areas.

Please refer to the EPA web site (shown above) for additional chemical storage information.  The following photos are used to illustrate some of the points listed above.

This is an example of what NOT to do.  (1) Notice the bottled water stashed on top of the bags of chemical.  (2) The bags are on top of a pallet, which is good practice.  (3) This area is readily accessible by any worker, including those who are not familiar with the hazards of the chemicals.  (4) There was no eyewash or safety shower in this mixing/storage area.  (6) As far as mixing areas go, this one is better than some.  There are mixing tanks nearby, which are covered and the floor is notably dry.

These containers are clearly labeled “flammable liquid”.  However, they are stored out in the open where any worker can have access to them.  In addition, they are stored in a hot environment.  There were no fire extinguishers in this facility and the employer had not established an emergency action plan for workers to follow in the event of a fire.

This is a good example of a chemical storage area at a greenhouse.  This storage area is a locked trailer that is well lit and ventilated.  Labels are intact and readable.  Spills would be easy to recognize.

Chemical storage with locked door and sign “Poison Storage Area”.  Note location of eyewash and safety shower.

Tina Daniels
HICAHS Safety & Health Consultant and
Extension Farm Safety Specialist
CSUCE Agriculture Health and Safety