Summer’s electric bills can be more expensive than winter’s with greenhouse cooling as the main use. Putting the following tips into practice can help reduce the useage.

Shut down greenhouses not in use

I frequently see ventilation equipment operating in an empty greenhouse. Turn exhaust and HAF fans off and open all vents, doors and rollup sidewalls. Use exterior or interior shade to reduce the inside temperature.

As exhaust fan ventilation is installed at 8 cubic feet per minute (cfm)/square foot floor area, it uses an estimated 0.4 to 0.6 kilowatt hours (kWh) of electricity per 1,000 square feet of floor area each hour. If operated 16 hours in a 10,000 square-foot facility, this would add from 64 to 96 kWh to the electric bill each day.

HAF air circulation fans are also frequently left operating. These are typically installed at about 2 cfm/square foot of floor area and, depending on model use, from 0.07 to 0.2 kWh/1,000 square feet. For 24 hours/day operation, this can add another 17 to 48 kWh/day to the above greenhouse electric bill.

Exhaust fans benefit from frequent maintenance

If the belt squeals when the fan starts, it is either loose or worn. To check the belt for proper tension, press in the center between the pulleys. It should only move a distance equivalent to the belt’s width. A belt with cracks or frayed edges should be replaced.

Shutters should operate smoothly. Examine for bent or stuck open shutters and lubricate bearings and levers when needed. Clean the fan blades and motor frequently. The layer of dust reduces air flow over the blades. Dirt on the motor traps heat and leads to overheating.

HAF fan maintenance is important in achieving high efficiency

Fan blade guards and motor casings pick up considerable dust from the air moving past them. It is important to clean these several times a year. Since fans frequently get moved out of position, they should be restrained by a bracket or chains to keep them stable.They should also be located to point horizontally towards the opposite endwall to transfer maximum energy to the air mass.

Turn hoizontal air flow fans off when exhaust fans are on or if vents are open

The horizontal air flow (HAF) disrupts the normal exhaust fan or natural ventilation air flow pattern decreasing ventilation efficiency. Install a relay that disconnects HAF when the ventilation system is activated.

Add a roof vent

To reduce electricity use, some growers are installing roof vents in their hoophouses. A 4-inch wide vent on the summer leeward wind side should be adequate with rollup sides. This allows heated air to escape through the roof, eliminating the need for exhaust fans. It also provides a more uniform temperature throughout the greenhouse. The cost of a motorized roof vent is $50 to $60/linear foot. In some states, the USDA NRCS – EQIP program provides grants for installing roof vents. Select an open roof design when building a gutter-connected house to eliminate the initial and operating costs of fans.

DON'T TRY TO OVER-COOL THE GREENHOUSE BECAUSE THE FANS WILL HAVE TO RUN MUCH LONGER TO GET THE LAST DEGREE OF COOLING.

Be realistic when setting the cooling control

Don’t try to over-cool the greenhouse because the fans will have to run much longer to get the last degree of cooling. To prevent short circuiting of the air, keep doors and vents near the fan closed. The control sensor should be located near the center of the greenhouse at plant height and shaded from direct sunlight.

Select high-efficiency replacement motors

Many older fan motors are in need of replacement. Although premium motors with 86% efficiency cost a little more than standard motors, they draw less current.

For example, a new premium 1 horsepower motor draws only 9.2 amps compared to an original capacitor start motor that draws 13.6 amps, which is a 32% savings in electricity. Premium motors also have shaft and bearing seals that keep out dust and dirt, moisture resistant grease and electronic control. Check with your local Natural Resources Conservation Service (NRCS) office about funding to replace the motors.

Tiny but mighty, these pests bedevil growers all over the world.

More than 6,000 species of thrips roam the planet, yet only five are of real concern for growers, attacking an array of crops from fruits and vegetables to ornamentals. The damage to these crops is a result of thrips feeding on developing plant parts, causing deformed or scarred leaves and flowers — and worst of all, transmitting various tospoviruses such as impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). One of the most reviled species of all is the western flower thrips (Frankliniella occidentalis), which quickly multiplies and ravages a wide range of host plants, but especially ornamentals.

At a mere 1 to 1.5 millimeters long in adulthood, these tiny terrors inflict damage through feeding. “They have a super-special mouth part that’s like a big needle that injects into a plant cell, sucking out all the fluids from it, causing the cell to collapse,” says BASF Sales Specialist Leah Van der Heide, a former ornamental grower in southern California. “Then they pull it out and move to the next cell, scraping the tissue as they feed away. They don’t discriminate. They’ll feed on basically any soft plant tissue, other than roots.”

Once a thrips punctures and feeds on that plant cell, not only does it cause a visible mark on the plant, but it also kills the cell. This is especially problematic when the pests feed on developing plant parts because “it causes all this messed up growth,” Van der Heide says, “and if that wasn’t bad enough, if a feeding thrips is carrying around a tospovirus, the virus will be transmitted to the plant. Which is bad … I call it the kiss of death.”

Growers can spot larvae — nearly transparent white or yellowish to orangey yellow, with a large head and bright red eyes — and adults, which range from white to yellowish orange to almost black. Thrips have “a pointy butt that emits tiny black specs of fecal matter,” Van der Heide says, “plus tan, silvery, necrotic areas on the leaf can be really noticeable if the feeding is heavy enough.”

What makes thrips funky is also what makes them hard to control. “Egg to adult can happen in as little as 10 days, and adults can live for 30 to 45 days, depending on temperatures,” she says. “Each thrips has four or five generations that have their own four to five generations that have their own four to five generations, and so on. Because these reproducing adults live for so long and their lifecycles are so quick, it’s tricky to control them once a population is established, where every life stage is present.”

So, what’s a grower to do? Van der Heide suggests an integrated approach.

Scouting. Check anything and everything that comes into the greenhouse. “If there’s a plant, there’s thrips,” she says, advising growers to check all incoming material. “Even if it appears clean, an egg may have been ovo-deposited inside any of the soft green tissue from wherever you got it” she says. “I assume that they’re always there; if they’re not there, they’re going to be there really quickly.”

Monitor all crops at all stages, Van der Heide says, with yellow or blue (colors that attract thrips) sticky traps placed right above the plant’s canopy. Growers can also use the “tap” method by gently tapping the plant, while holding a white piece of paper below. If present, the pests will fall off the plant and onto the paper, where you can easily see and count them.

Blowing on flowers can also uncover hidden thrips “They hang out in the flower — adults especially. So, just blow inside the flower — the carbon dioxide agitates them, and they move around,” Van der Heide says.

Prevention. Isolate and inspect incoming material. “Consider implementing dip applications of Nemasys® beneficial nematodes, Steinernema feltiae, oil and/or Velifer® fungal contact insecticide miticide, Beauveria bassiana, for unrooted cuttings, plugs and liners” she says. And confine infected plants to one contained area. “Don’t move infested plants to other growing areas because the thrips can easily spread to neighboring clean plants. When you move plants around, you’re literally doing the job for them,” she says.

She adds that thrips are “little hitchhikers” that can be carried by wind and on employees’ clothing. “If possible, be sure that the staff works in clean areas first, ending up in the not-so-clean areas at the end of the day.” Using properly positioned fans that blow air outwards at facility entrances can also help to knock any stow-away pests off entering personnel.

Since thrips travel so readily, growers should screen vents and greenhouse doors, and shouldn’t leave greenhouse doors open. Also “Be clean — weed control is huge,” Van der Heide says. “Sweep up dirt around the growing area as thrips drop to the floor and into soil to pupate.”

Control. And if, despite all best efforts a thrips invasion occurs, Van der Heide says, “Literally everything you learned in school about pest management needs to be applied.” She recommends bio-control agents (BCAs) in combination, since each BCA targets a different life stage. For example, the predatory mite Amblyseius cucumeris only feeds on the first larval stage of thrips. While Orius insidiosus is an excellent thrips predator, “they can be very sensitive to chemicals – even a little residue can harm them, so make sure you’re releasing them early in the crop and avoid incompatible chemistries. Just be smart.”

Conventional chemistries, Van der Heide says, can be effective and will most likely be required at some point. But keep in mind: “There is known resistance to certain chemicals, so you have to make sure you’re rotating your mode of action and using insecticides in a very targeted, accurate approach at the right time, when it’s really required.” For example, Pylon® miticide-insecticide, chlorfenapyr, is “freaking amazing,” she says, “but it will harm beneficial insects and mites. The idea is to implement biological strategies early on, keeping pest populations low for as long as possible. Then, when the time comes to bring out the big guns, chemistries like chlorfenapyr and spinosad will work EXTRA well.”

Most of all, Van der Heide says, “You’re not alone. It’s okay. Ask for help. We can do it.”

In January, the Horticultural Research Institute announced its latest round of funded projects, including ‘Developing environmental and cultural protocols for the production of containerized succulents in greenhouses and nurseries’ from Dr. Roberto Lopez, assistant professor at Michigan State University, and W. Garrett Owen, extension specialist at MSU. The project is one of two MSU projects to receive funding from HRI; the other is ‘Benefits or features: Which cue is more effective on retail signs?’ from Dr. Bridget Behe.

Greenhouse Management: What led you to do succulent research?

Roberto Lopez: When I have visited growers — not just in Michigan, but around the country — everyone is growing succulents. So I ask them, ‘Where are you getting your production information?’ and most said that there is none and that they are growing them just because they are popular. So it got me thinking that if they could streamline the production of succulents, they could make even more money. There are also growers in Northern latitudes who struggle with succulents because they grow slowly and they end up having them in the greenhouse for six months or more. That’s really what this research is looking at.

GM: Why aren’t there already widely known best practices for succulent production in place like there are for crops like bedding plants?

RL: To date, there’s only been research primarily done at Virginia Tech and at the University of Minnesota, and on different aspects of the plants. So, for example, Garrett is going to be working on nutrition [in our study]. Right now, there are people that say succulents need very little fertility and others that say succulents need a lot of fertility. So what he’s going to look at is that question and find out how much fertility these plants really need. I’m going to look at basically photoperiod and see if, based on our preliminary findings, growing them under long days can allow you to double the growth in about six weeks. We are going to cover the main ones, mostly, like echeveria, crassula and agave.

GM: When you’re approaching a project like this and designing the work you are going to do, what do you find to be the most challenging part of getting the most value for the end grower?

RL: I would say trying to get consistent material so we can repeat the studies [in the future]. Again, succulents are so popular that we may be able to get a cultivar now. But let’s say that cultivar is available now; that cultivar might not be available [in six months] because there is just so much demand. With how they were grown so far — often in California, sometimes outdoors — growers in the Midwest and the Eastern U.S. growing them in greenhouses had no information available to grow them quickly.

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