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Winter Greenhouse Prep

January 24, 2017 |

By Turner WalstonGreenhouse1_web

Follow these five tips to make greenhouse spring cleaning a breeze.

With tobacco out of the fields and cover crops planted, ‘tis the season to prep tobacco greenhouses for 2017 transplants. “Sanitation is the key word,” says
Dr. J. Michael Moore, professor and tobacco Extension agronomist at the University of Georgia. “That means you’re going to try to leave behind all of the pests that may have affected your crop in the previous year.”
With help from Moore, here are some tips to get you ready for spring planting.

1. Replace plastic bed liners.
The plastic liners used in float greenhouses serve as a barrier between the water in the reservoir and the soil. The use of these liners allows growers to add only the nutrients and pest control agents necessary. Replace plastic bed liners to begin the growing season with a sanitary pool for float trays.

2. Wash float trays.
Almost 100 percent of tobacco seedlings are produced in float trays. The polystyrene trays most often employed by growers can collect pathogens over time. To help prevent the spread or reinfection of plants, trays should be washed thoroughly, under pressure, with detergents specifically designed for this purpose. “Chlorine, while it’s a good cleaner, tends to leave residue on the trays that can negatively affect tobacco transplants as they grow,” Moore says.
Despite popular belief, trays can’t be thoroughly cleaned with just the use of a pressure washer due to the porous nature of the trays. While a pressure washing might result in a nice-looking tray exterior, the roots of tobacco transplants can grow in the tiny spaces in the trays. When the plants are removed, pieces of the roots can be left behind. “If they’re from plants that were affected by pathogens, that means we also have the pathogens embedded in those spaces,” Moore says. “It’s next to impossible to get in and clean out all of the pathogens that can reside.”
With the phase-out of methyl bromide, there isn’t a real fumigant substitute to date. Carolina Greenhouse and Long Tobacco have brought steam tray cleaners to the market that can do a thorough job of sanitation. Trays are stacked in the cleaners, and the introduction of steam and temperature sanitizes the trays.

3. Make a note of tray use life.
Polystyrene float trays can become heavy and brittle as they age, and they often retain fertilizer residue and pesticides from previous years. That can lead to variability in plant growth between old and new trays, even in the same greenhouse.
Experts recommend replacing 10 percent of float trays per year. Recently introduced all-plastic float trays have a longer use life, as they are not permeable to root growth and do not carry over pathogens year to year like polystyrene trays. “Certainly, they are making some headway,” Moore says with regard to plastic trays. “It would be much easier to sanitize the plastic tray because you know that it’s not permeable.”

4. Don’t smoke in or around greenhouses.
Introducing old tobacco products into the greenhouse after production begins can be devastating to tobacco transplants. Tobacco mosaic virus can be transferred mechanically, meaning it can go from an infected cigarette to a transplant if proper precautions are not taken.
“You might say, well, that’s only one plant in a million,” Moore says, “but as you begin to clip the plants to promote uniformity, you sling the juice of that one plant onto thousands every time you use the mower. Many times, we may be mowing six to eight, even 12 times per season. You can infest the entire house and a farmer’s entire operation.”
It’s a good general rule not to smoke or use tobacco products in or around greenhouses, and growers using these products should wash their hands thoroughly before entering. “Of course, the next thing would be to tell everybody, whether they’ve used those products or not, not to be touching the tobacco transplants because of the potential for transferring something they don’t know that they have on their hands,” Moore says.

5. Sanitize mowers.
Similarly, it’s important to sanitize mowers on a regular basis to wash off the plant residue and tobacco juice that accumulates with a detergent or bleach solution. “Most mowers are not cleaned as often as would be recommended,” Moore says. “We’ve been very fortunate over the years to have a very minimum number of instances where this particular virus caused major issues. Still, the threat is always very real.”

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