As National Greenhouse Manufacturers Association’s President, I am proud to represent a great and growing industry. Our organization has taken a leading role in promoting best practices through education and networking. We also work diligently on behalf of not just our members, but the entire greenhouse manufacturing trade on building codes and standards.

Sharing knowledge and passion about their industry, NGMA members took every opportunity to listen and learn at the organization’s annual Spring Meeting held in April in San Diego, California. The meeting gave attendees the opportunity to assemble as a collective group to discuss, collaborate and educate ourselves on topics that directly affect our industry. We heard presentations on topics like: Construction Contracts, Risks and Insurance; Fan Energy Regulation; and State-of-the-Art Supplemental Lighting for Controlled Environments. There was also a session on the key aspects of greenhouse lighting from both a practical and technical perspective.

During the past few years, our Codes and Standards Committee has worked tirelessly updating the greenhouse definitions in the IBC Building Codes. It is exciting to see the NGMA code sponsored changes are now in use as the 2018 IBC gets adopted by different jurisdictions. Specifically, a reclassification of greenhouses in the code specific to its use, a 60 percent-plus increase in allowable square footage for a greenhouse before sprinklers and other fire protection systems are required. Additionally, and what should be considered a huge victory, a specific greenhouse definition and a section were added within the codes for future greenhouse regulatory clarifications.

As we move forward, our attention will turn to the Energy Codes changes being proposed and begin the 2021 structural review. Our influence in this area is vital to our industry. As an organization, we want to ensure that modifications to code guidelines will not have an adverse effect or place unrealistic demands on growers.

For 2018, our Communication Committee plans to roll out a new website that has improved functionality and easy user interface. It also plans to offer webinars featuring NGMA speakers, who will speak on a variety of industry topics, as well as promote the value of the NGMA and its members.

I want to personally thank the many volunteers who contribute to the success of NGMA. We have made progress with various initiatives, and I look forward to continuing to serve as President in 2018.

Mark Davis

President & CEO

Atlas Manufacturing, Inc.

Flue gases are best described as an unseen enemy that can compromise yield and plant quality in a few short hours. Often a small hole in the flue pipe or small holes in the heat exchanger can cause these colorless odorless gases to leak out into the growing area. In some cases, a missing flue cap can allow flue gases to be blown back down the flue pipe into the growing area below, resulting in significant injury to sensitive crops.

Several years ago, an experienced grower lost his tomato crop when sulfur dioxide-laden flue gases blew down his uncapped flue pipe into the greenhouse. This grower lost his entire crop due to a missing flue cap and a sudden downdraft during a spring thunderstorm. Sulfur dioxide is injurious to most crops when plants are exposed at 0.48 ppm for four hours or 0.28 ppm for 24 hours (Thomas, 1961).

Ethylene is the most subtle, but perhaps the most injurious, of the flue gases. Ethylene can pass through the smallest of holes on the flue pipe or through holes in the heat exchangers into the growing area.

Unvented propane heaters that are sometimes touted as vent-less heaters often produce ethylene as a byproduct of combustion, leaving this growth regulating substance behind as a stark reminder of its presence.

Tomatoes are often one of the most sensitive crops to ethylene and the downward bending of the stems (epinastic growth) is typically the first symptom noticed by a discerning grower. In some cases, the grower may misidentify the causal agent, which leads them to incorrectly employ an array of crop protectant chemistries to avert crop loss. Tomatoes exposed to 1 ppm of ethylene for 3 hours or to 0.1 ppm for 24 hours will display symptoms of epinasty.

As greenhouses are fired up across the world, please carefully inspect your furnaces and flue pipes immediately. Low concentrations of flue gases can impact crop yield and plant growth, so consider the following steps for a successful cropping year:

• Make sure that your flue pipe extends a few feet above the roof line of your greenhouse.
• Ensure that a cap is used on the flue pipe to prevent flue gases from being blown down the pipe and into the greenhouse.
• Inspect the heat exchanger for cracks and holes that can lead to flue gas leakage into the greenhouse.
• Ensure that exhaust/ventilation fans are not running when the furnace is in operation, since they could potentially suck flue gases into the greenhouse.
• Make sure that you have a fresh air inlet in place to provide enough oxygen for proper combustion. Generally, a minimum of one square inch per 2000 btu of heat output is required.

Editor’s note: This article originally ran as an e-Gro alert. Thomas is an area commercial horticulture educator at Penn State Extension.

Thermostats are still the major heating/cooling system control device for many growers. Although accurate mechanical and electronic thermostats, controllers and computers are readily available, they have not been widely adapted in many smaller operations due to their cost and unfamiliarity to growers. Selecting the right thermostat and locating it to sense plant temperature can save considerable fuel and electricity.

Best location

I have seen thermostats located on end walls, attached to the heater or fan, above fin radiation, in direct line of heat from a furnace and in direct sunlight. If yours are in these locations, they should be moved. They will not provide accurate plant temperature sensing there.

Locating the sensor near the center of the greenhouse or crop area is best as it reduces the effect of heat loss through the glazing. Keep them away from operating equipment, dripping water or a dusty location. Use a chain to hang them so that they can be kept at plant level. Locate heating and ventilation equipment thermostats in the same area so they sense the same air.

Shielding is important

Thermostats and sensors should be shielded from direct sunlight as this can give false readings. A good installation is to place all thermostats inside a closed aspirated box that has been painted white. With a screen on one end and a small muffin fan on the other, air will be drawn through and all sensors will get the same temperature air. This technique is standard on most controller and computer control systems.

Clean your sensors

I have seen thermostats coated with a 1/4-inch-thick layer of dust. This will result in inaccurate readings. Use a can of compressed air to blow the dust off the sensor and the box. Purchase thermostats with a sealed box and use watertight electrical connections.

Loss of accuracy

Thermostats and sensors tend to lose accuracy over time. They should be checked at least once a year. I have had growers tell me that even new thermostats were inaccurate by as much as 10° F.

It is easy to check the accuracy of a thermostat. Start by checking the accuracy of a thermistor or thermocouple thermometer. These are inexpensive, fast-acting and have an easy readout. Insert the probe into an ice water bath. The reading should be 32° F.

After allowing the thermometer to reach room temperature, place it next to the thermostat sensor. Slowly move the dial until the heater turns on. The reading should be the same temperature as the thermometer reading. If not, determine the temperature difference and mark the thermostat accordingly. The next time the heating system is serviced, have the serviceperson recalibrate the thermostat.

Thermostat selection

The harsh greenhouse environment requires a good thermostat. Select one that has a hydraulic sensor activated by pressure from the expansion of a liquid or gas in a closed tube coil.

The movement of the switch between the On signal and the Off signal is called differential. This can vary from 2° F to 8° F. For example, if you have a setpoint of 60° F and a thermostat with a 5° F differential, the heater will start when the temperature reaches 60° F but doesn’t shut off until 65° F. Every degree above the setpoint increases heat loss from the greenhouse and heating cost by about 1.5%. It is important to select a thermostat with a +/- 1° F differential. The Dayton thermostat used by many growers has a differential of +/- 3° F.

The savings can be significant. For example, for a 30-foot by 100-foot greenhouse the savings between a 2° F differential and a 6° F differential thermostat can be as much as 500 gallons of fuel oil, 750 gallons of propane or 700 therms of natural gas over the fall to spring heating season. The payback is short.

Good controls that are maintained properly provide heating/cooling equipment with a means of operating at peak performance and efficiency. Now is the time to maintain, calibrate and replace the controls in your greenhouses.

John is an agricultural engineer, an emeritus extension professor at the University of Connecticut and a regular contributor to Greenhouse Management. He is an author, consultant and certified technical service provider doing greenhouse energy audits for USDA grant programs in New England. jbartok@rcn.com

Photo courtesy of Bob Dickman

Dickman Farms was looking for a better way to control insect pests when it turned to using biological controls. The insects in its houses were developing resistance to the sprays, and the REI for these products resulted in lost productivity, not to mention were an inconvenience.

“The main reason we switched over was resistance to chemicals that controlled western flower thrips,” says Bob Dickman, greenhouse manager with Dickman Farms. “It’s very difficult for insects to become resistant to being eaten or parasitized.”

Dickman Farms is a fourth-generation, family-owned wholesale greenhouse and retail operation that first opened its doors in 1903. Dickman Farms consists of 10 acres of greenhouses and a full-scale garden center/retail store.

It is located in the Finger Lakes region of Central New York. Starting out with a few thousand young plants, it now sends more than 10 million starter and finished plants throughout the country and into Canada.

In one case, Dickman says they fogged an entire range with a popular pesticide used in the greenhouse industry and burned 2,000 mixed baskets. It had become an time-consuming endeavor with decreasing value for the business.

Enter biocontrols. The Dickman team began to learn all they could about biocontrols via trade shows, the internet and trial and error. They also took the advice of other growers who were already using this approach to insect control, including Ronald Valentin, who introduced the company to this method six years ago.

Graphic courtesy of Rose Buitenhuis, Vineland Research and Innovation Centre, with pictures from OMAFRA and Liette Lambert

Advantages of using biocontrols

There are many advantages to using biocontrols over traditional sprays, one being that you don’t get the foliage wet when using biocontrols like you would with chemical sprays, Dickman says.

“We don’t need to overhead spray chemicals on open blossoms during peak production to combat thrips and aphids,” he says. “Keeping the flowers and foliage dry has helped the overall plant quality and reduced fungal and bacterial diseases. When we would spray overhead for thrips and aphids, we would wet the flowers. We would then have to go back with a fungicide.”

At Dickman’s, the REI for the chemicals they used was at least 12 hours, resulting in lost productivity.  

“It was very difficult to get workers back into the greenhouse areas that were treated during the work day,” Dickman says. Another important advantage of using biocontrols is not having to worry about the potential negative health impacts from using chemicals. Biocontrols are also more in tune with consumer demand for pesticide-free plants, he says.

In terms of economic benefits, Dickman says there are the obvious savings in labor in terms of the amount of time it takes to spray a crop and the lost productivity when a house is closed up after it is sprayed. Also, fewer workers need to be licensed to apply pesticides, and the potential for a lawsuit over a pesticide exposure is eliminated. In terms of immediate savings, Dickman Farms reduced its chemical use almost immediately, from 1.0 percent of sales to pay for chemicals in 2012 to 0.9 percent in 2013.  

“2018 has been our best year yet for biocontrol.” –Bob Dickman

And finally, the effective use of biocontrols will ensure that plants aren’t being delayed from being shipped due to having to spray an infected crop before it gets on the loading dock. This would delay shipping at least until the REI period is over.

Using banker plants

Banker plants play an important role in Dickman’s biocontrol program. The banker plants provide an alternative food source for beneficial insects, should they run out of the pest insect, and in some cases a reproduction site for them, according to Michigan State University Extension specialists.

For instance, pollen from ‘Purple Flash’ ornamental pepper plants will provide food for the insidious flower bug (Orius insidiosus) should it run out of thrips to prey upon.

Oats and wheat will provide a food source for the beneficial insect Aphidius colemani should it run out of a supply of aphids. And Dicyphus hesperus will dine on plant sap should it gobble up all the whiteflies in the greenhouse.

MSU experts recommend about 100 pepper banker plants per acre of production space. Mullein is another banker plant they recommend. It is used for biological control of whitefly that potentially infect poinsettia crops, as well as tomatoes and cucumber cropping systems. Forty mullein plants are used per acre of production space.

Dickman’s uses oat banker plants for aphid control and ‘Purple Flash’ ornamental peppers for thrip control on Lobularia. It also uses sachet packets for thrip control and beneficial nematodes to control fungus gnats and shore flies.

Dickman says their biocontrol program has been very successful, though it didn’t come overnight.

“2018 has been our best year yet for biocontrol,” he says. “Every year we get a little better at using biocontrols and the staff — not just growers — recognize problems quicker.”

Dickman says they don’t hire a person specifically for scouting, but it is necessary to have someone on board who has a passion for using biocontrols. Dickman Farms relies on two section growers to do most of the scouting, along with a garden center employee.

“The biggest challenge is being able to identify the greenhouse pests from the beneficial insects,” Dickman says. “When we first have someone start out scouting, they will scout with the section grower for the first three to four weeks so they can get trained recognizing the different insects on the sticky cards as well as in the crop.”

“Overall, we have better control with our beneficial program than we did with our traditional chemical application program,” he says.

The bottom line with biocontrols

“You have to be patient and be preventative,” Dickman advises. “Start out using small trials on specific crops you have struggled with in the past using chemicals.”

“If you have an outbreak of pests, biocontrols will never catch up to the population of the pest before too much damage has occurred,” he adds. “A grower will have failures in their biocontrol program — we have had plenty. [The] first thing is to learn from the mistake that has occurred, try not to make the mistake again and don’t give up on bios because you didn’t get the control that you had hoped to achieve. Lastly, seek out advice from other growers and suppliers. There is a lot of work that goes into launching a beneficial program. Make sure you have ‘buy-in’ from everyone on the team.”

Neil is a freelance writer/copywriter for the green industry. greenindustrywriter.com