Sanitation to sticky cards: controlling pests and diseases in the spring

The spring rush in the greenhouse could be compared to a restaurant where a large crowd arrives unexpectedly. A mess is being created in the kitchen as workers are making sure orders are being filled in a timely manner. Likewise, in the greenhouse it’s getting messy as well: plants are moving off and on benches, carts are going in and out. Cuttings are being prepared to be stuck so they can be propagated. Meanwhile, insects and disease spores are trying to take advantage of the situation.  

Growers have to be diligent in this industry to stay ahead of disease and insect problems in the greenhouse, especially during the mad rush of spring. Julie Iferd knows all about it. She’s in charge of growing operations at Catoctin Mountain Growers, a 15-acre greenhouse operation located in Keymar, in north central Maryland. They supply annuals to big box stores and a few grocery chains and landscapers. Needless to say, the crops coming out of their houses have to be clean of insects and disease, which is a challenge during the busy growing season.

Iferd says they start seeding early spring crops in November and December, but it isn’t until about early February when she starts feeling the pressure. By then, they’re working with vegetative cuttings, sticking and then transplanting into pots.

“It’s called a mad rush for a reason,” Iferd says. “It is difficult having so many crops in one area at a time,” she says. “Knowing and monitoring specific crops for specific problems — there are groups of plants that are more likely to see either an insect or disease problem. Just keeping track of it all at the same time can be a lot.”

Sanitation: the first line of defense

Sanitizing the greenhouses prior to planting and propagation is the first line of defense against insect and disease problems.

“Before we start the season we clean and sanitize the floors with Green-Shield,” says Bob Dickman, greenhouse manager at Dickman Farms, located in the central New York town of Auburn. “We focus on the drains to make sure all debris and soil are removed. We use Strip-It to clean all of our hanging basket lines and drip headers.” He says they also like to “cook” away the germs and bugs by closing up the vents and heat retention curtains for a day. They also avoid carrying plants over from year to year.

During the busy growing season, which Dickman says peaks for them in Week 10, floors and walkways are cleaned daily. They use a ride-on power sweeper for the main walks. To make sure nothing gets past them, workers have to follow a certain protocol to ensure no stone goes unturned in their 400,000 square feet of growing space.

“Sanitation is everyone’s responsibility in the greenhouse,” Dickman says. “We have a checklist for each department to sanitize pruners, patching tools and belts every night. We also make sure everyone is cleaning their area every day.”

To further prevent disease and insects from spreading, they wear lab coats and gloves when they are sticking cuttings, trimming plants and handling material in the greenhouses. Using footbaths is part of the daily protocol; the footbaths are positioned at thresholds throughout the facility. And like any establishment, they demand workers wash their hands frequently and they enforce a smoke-free workplace to eliminate the risk of tobacco mosaic virus.

Bye bye poinsettias, hello spring flowers

For the staff at Catoctin Mountain Growers, preparations for the mad rush of spring begin after the last poinsettia has shipped, right around the first of the year. Iferd says they’re lucky to have all concrete floors, which makes the task of cleaning the floors and keeping them clean a little easier.

“After poinsettias are shipped, we do extensive cleaning by sweeping all floors then using a quaternary ammonium to sanitize the floors and walls,” Iferd says. “If there are any drips or puddles on the floors that cause algae spots we clean those up with either a power washer or a hydrogen peroxide product.”

Staying one step ahead

Despite the pressures in the spring to get a crop finished and out the door, Iferd says they’ve never let insects or diseases get out of hand.

“We have thankfully never had to destroy an entire crop, or even any large number of plants,” she says. “But there is something to be said for getting rid of the epicenter of a problem. If we find a basket loaded with aphids, we will dispose of it and treat the remaining baskets that have or may have lower levels of aphids.” She says the same can be said for preventing the spread of disease.

Should disease and/or insect problems get out of hand, Iferd says growers should “cut their losses” and destroy infected plants, rather than letting the problem get worse.

“No chemistry is ever 100 percent — you have to keep after it,” she says. “If an infection is bad enough, you might be better off getting rid of it, but that’s a tough thing to do.”

As if keeping an eye on your own crop is not enough, growers also have to thoroughly inspect incoming material, such as cuttings they use for propagation purposes.

“We have had unrooted cuttings shipped in with TMV as well as Agrobacterium.” Dickman says. “Unfortunately, we had to destroy these liners.” He says this was a stock cutting issue that was beyond their control. He adds they’ve never had a pest or disease outbreak in their finished crop where they had to destroy or quarantine an entire crop.

“We have put a concentrated effort on scouting and recording pests in the greenhouse to be proactive at spot spraying before the product ships,” Dickman says. “The growers have dedicated times where they scout each week. No exceptions. We also follow a strict spray rotation and weekly fungicide drenching.”

He added that they’re currently at 95 percent biological control in their finished plant production. For thrips they use Amblyseius cucumeris from both Bioline and Biobest. For aphids they used a comprehensive strategy involving oats and parasitic wasps.

Iferd says all their growers are trained in IPM, and it is their job to monitor crops on a daily basis.  

“We use sticky cards to keep track of any flying insect populations,” she says. “Daily handling of the plants to look for other insect and disease pressure is essential. You need growers to tip out pots and look at roots and on the undersides of leaves for problems. Our shippers are the final line of scouting — they have some training in basic insect and disease issues. If there is anything even remotely suspicious-looking about a plant, they know to get a grower to determine if it is a problem.”

Communication is key

Both growers acknowledged the importance of communicating with other growers and workers during the spring rush.

“As a new crop moves into a grower’s section, I always try to discuss the likely pitfalls of that particular crop,” Iferd says. “There are some crops that have certain problems, what to watch for — every crop is different.” She says she communicates with workers on an individual basis to achieve this objective.

At Dickman’s, they set up checklists and enforce them. “We have to communicate to all of our departments the importance of staying clean,” Dickman says. “When we’re busy, we can forget simple steps like cleaning racks as they come back from a customer. Each department needs to own the protocols and procedures,” he adds. “It’s difficult to enforce if you don’t have a game plan and everyone on board with your IPM procedures.”

“We conduct a weekly grower meeting,” he adds. “Each grower communicates what insect and disease pressure they are seeing in their designated ranges. I also walk crops to follow up on their scouting reports.”

During the mad rush of spring, don’t rush by the steps and practices necessary to ensure you’re delivering an insect and disease-free crop to your customers.

Neil is a horticulturist and freelance copywriter for the green industry, assisting businesses with advertising copy, white papers, blog posts, articles, and other digital content. greenindustrywriter.com