Plant protection of greenhouse-grown vegetable crops involves implementing a variety of strategies in order to alleviate problems with insect and mite pests, including sanitation. This is one of the easiest and least expensive practices to implement because sanitation can be performed during regular operating hours.

Inside and out

First, weeds located inside and outside the greenhouse provide refuge for many insect and mite pests, including aphids, leafminers, thrips, spider mites and whiteflies. Consequently, weeds allow insect and mite pests to survive and potentially disperse onto vegetable crops.

The weeds that serve as refuge for insects include: sowthistle, Sonchus spp. (aphids and whiteflies); oxalis, Oxalis spp. (thrips); and dandelion, Taraxacum officinale (whiteflies). Many weeds also serve as reservoirs for pathogens (fungi and viruses) that can be acquired by insects while feeding, and then subsequently transmitted, when feeding on vegetable crops including tomatoes and cucumbers.

Weeds that serve as reservoirs for viruses, specifically the tospoviruses, impatiens necrotic spot and tomato spotted wilt virus are: chickweed (Stellaria media), lambsquarters (Chenopodium spp.), nightshade (Solanum spp.), oxalis (Oxalis spp.), shepherd’s purse (Capsella bursa-pastoris), pigweed (Amaranthus spp.), and bindweed (Convolvulus spp.). An abundance of weeds underneath benches with soil flooring may retain enough moisture, thus providing a favorable habitat for fungus gnats and shore flies to breed.

Take action

A long-term strategy that should be implemented to reduce problems with weeds is installing landscape or fabric barriers, which are geotextile, non-biodegradable materials that prevent weeds from emerging from the soil and underneath benches. There are herbicides (weed-killers) registered for use in and around greenhouses, although caution must be exercised when applying herbicides inside greenhouses, especially those with vegetable crops. A pre-emergent herbicide may be applied prior to weed emergence, whereas a post-emergent herbicide is applied after weeds emerge.

However, be sure to avoid any inadvertent plant injury (phytotoxicity) when using herbicides, especially those that have systemic (when applied as a spray) and post-emergent activity. In general, apply herbicides when greenhouses are empty. Always read the label directions before mixing and loading to ensure that the herbicides can legally be used in greenhouses where vegetables are grown. Weeds that are mature or greater than 15.2 centimeters (6 inches) tall should be removed by hand, taking care to remove both the aboveground portion and roots. Areas or weed-free zones around the greenhouse outer perimeter [3.0 to 9.1 meters (10 to 30 feet)] will help to reduce the migration of insects, such as western flower thrips (Frankliniella occidentalis) and greenhouse whitefly (Trialeurodes vaporariorum) adults, and winged aphids through natural greenhouse openings (e.g. vents, sidewalls, and doors), which will decrease the incidence of disease transmission.

Out with the old

Plant debris or residues such as old leaves, fruit, and growing medium may also provide refuge for certain insect and/or mite pests. Insects and even mites can migrate to fresh plant material as plant debris desiccates. For example, a study (Hogendorp and Cloyd, 2006) showed that plant material and growing medium debris placed into uncovered refuse containers can be a source of insect pests. As plant material desiccates, adults can migrate onto the main crop. In addition, certain insect pests that were initially larvae, nymphs, or pupae when plant debris were placed into uncovered containers may develop into adults that can fly out of the container, and potentially infest the main crop.

Another study (Hausbeck and Moorman, 1996) indicated that plant debris deposited into uncovered containers may allow fungi such as gray mold (Botrytis cinerea) to sporulate. This results in the release and dispersal of spores, via air currents, that may infect the main crop. Always place debris or residues into refuse containers with tight-sealing lids. Also, growing medium debris may provide sites for fungus gnat adults to lay eggs and western flower thrips to pupate. A broom or shop vacuum can be used to remove plant or growing medium debris; however, avoid sweeping aggressively as this may distribute fungal spores in the plant debris throughout the greenhouse.

Old vegetable plants or those remaining at the end of the growing season should also be removed because they can be a potential source of insect and mite pest populations. They can serve as reservoirs for the viruses transmitted by insects such as the western flower thrips. Another important sanitation practice is to immediately remove any vegetable plants from the greenhouse that are heavily infested with insect or mite pests.

Raymond is a professor and extension specialist in horticultural entomology/plant protection at Kansas State University.

References

Hausbeck, M. K., and G. W. Moorman. 1996. Managing Botrytis in greenhouse-grown flower crops. Plant Disease 80: 1212-1219.

Hogendorp, B. K., and R. A. Cloyd. Insect management in floriculture: how important is sanitation in avoiding insect problems? HortTechnology 16: 633-636.

Insects are often the first pests to come to mind as a threat for any indoor produce grower, but what about their larger counterparts? Birds and sometimes rodents flock to the warmth and shelter of controlled environment productions looking for food and safety from their predators, but they can become both a hazard for workers and your wares if not dealt with swiftly.

The dangers of these pests include spreading disease through the air, plants and produce, and disruption of your growing media, leading to crop loss.

Cory Gellerstedt, co-president of Nixalite of America Inc., says that birds and rodents can transmit more than 60 diseases which can affect greenhouse production, many times through their feces.

“Especially if you have food-producing plants and a lot of accumulation of bird guano, a lot of times it can build out, become dried out, and becomes airborne,” says Gellerstedt.

In rare occurrences, rodents can also cause significant damage in a greenhouse by feeding on germinating seed, roots, bulbs, shoots and young plants.

Gellerstedt, Bird-X representative Joshua Pierce and Robert Corrigan, president of RMC Pest Management Consulting, weigh in on how growers can prevent, identify and treat avian and rodent pests.

Find the culprits

From open doors to structural discrepancies, larger pests enter greenhouses through both obvious and discreet entrances.

“One of the most obvious and one of the hardest to control is open doors. People keep the doors open, and birds can fly right in,” says Gellerstedt. “Try to keep the doors sealed up. Birds can also get into little holes. Sparrows are very good at finding tiny holes and getting through them to gain access into the greenhouses.”

Pierce says those small holes in your defense are often found where the soffit and fascia meet.

“Basically, where your rooftop meets your house,” he says. “A lot of times, there [are] these little cavities that they can get into, [even] if it’s really narrow, they’ll definitely squeeze in.”

Venting systems without netting are also prone to both bird and rodent intrusion, says Pierce.

“If you have any type of cavities or voids where these animals can get in at the roof line or the land area, the best way to reroute these animals is to close off those cavities,” he says.

Also, pilings of junk resting on the exterior or within greenhouses can become a safe place for rodents to settle in.

“If there are any junk piles inside or outside the greenhouse, they will harbor beneath the junk,” says Corrigan. “Sometimes, mice will dig small burrows below the walkways of the greenhouse and live in the soil. Rats will sometimes live in any exterior piles of trash or any nearby structures that will give them adequate harborage. But because rats are so large, they are often not major rodent pests of greenhouses.”

Remove intruders

If you have found that these pests have made your greenhouse their home, the first step to a more sanitary facility is elimination through techniques such as trapping, chemical fog or using a laser pointer.

“Let’s say you have one starling or one sparrow, turn off all the lights, open up all the doors and [use] a simple hand laser pointer,” recommends Pierce.

For a larger, high-ceiling facility, he says another option is the use of larger netting trap with sloping poles. However, if your feathered invaders have settled into a nest in your facility the problem should be handled with more finesse.

“Some of these species are really quite protected,” cautions Pierce. “Some [laws concerning moving bird nests] vary from state-to-state [so] it’s important to contact your local pest control operator or a bird control manufacturer.”

If there are rodents in or around any type of greenhouse operation, Corrigan says they have found what they need to live and thrive: shelter, food and water.

“A grower should do everything possible to eliminate the harborage potential, because it is obviously difficult to restrict the vegetables for which the rodents may be entering into the house,” he says. “Should rodents get a foothold despite good sanitation and the rodent proofing of the greenhouse, controlling the infestation is not easily [achieved] by a do-it-yourself approach. All infestations are best handled by certified pest professionals.”

Fend off the fleet

“If [growers] can net off their venting, they’ll usually never have a problem with additional rodents as well as birds,” says Pierce.

Gellerstedt recommends also putting a net up in the rafters of your greenhouse or storage areas to prevent birds flying up out of reach and nesting.

For the future prevention of rodents, Corrigan suggests strict organization and cleanliness in and around your operation.

“A high level of clutter control will prevent rodents from getting a foothold and thriving. For example, never allow any accumulation of wood, lumber [or] scrap piles on the property, especially along the exterior walls of the greenhouses,” he says. “All trash containers on the property, large and small, must always be maintained in a clean and organized manner, so that the rodents are not drawn to the property in the first place. The grower should inspect the house and rodent proof any and all doors. Look for any obvious holes in the greenhouse's foundation and repair [them] to ensure there are no holes larger than a quarter-inch.”

Karen E. Varga also contributed to this article.

When 53-year-old Donna Williams left corporate America for a life of sustainable agriculture five years ago, she brought with her the understanding that corporate office culture is linked to employee wellness.

Offices across the U.S. are implementing exercise programs, supporting smoking cessation and encouraging healthier diets for their employees. For Williams, founder of Field Goods, connecting professionals with local healthy resources was a no-brainer.

“We have nutrition study data which shows that when people subscribe to us they get healthier,” she says.

Field Goods is a subscription-based food distribution service that relies on local produce from 80 farms in the Hudson Valley area of New York and in Fairfield County, Conn. Since its inception, the company has grown from 60 customers to more than 500 deliveries per week to offices throughout the area.

“It doesn’t cost employers anything,” she says. “We had one employer, Fujifilm, [for whom] it radically changed their culture and had a huge impact on their employees’ behavior.”

But what’s the draw for growers?

The year-round program not only links office employees to produce grown traditionally across acres of small farms, it also utilizes controlled environment agriculture in the area.

“We love our greenhouse guys, they save our bacon every winter,” says Williams. “We have about four hydroponic/aquaponic growers, a pair of heated greenhouses growing in the ground and about half a dozen farmers that extend their crops’ [seasons] through high tunnels.”

Williams says the reason she founded Field Goods was to give small local farmers a “leg up” getting their produce to market and to try new products.

“We work with our growers to help their operations,” she says. “For instance, we have a hydroponic grower who was selling us live plants, but he was having growing inconsistencies in their heights, so we said to just give them to us as fresh salad mixes.”

Subscribers simply determine the size of bag they would like delivered to their office, a choice that can be modified based on need, or paused while on vacation.

“And we select what goes in the bag, which I think is why our service is particularly compelling from a wellness perspective, because it gets people to try things they would have never tried before,” says Williams.

Produce grown under cover comes into high demand for the company between December and May.

“We’re getting more leafy greens, like baby kale and even cucumbers,” she says. “We can never have enough greenhouse product.”

The consumer draw lies in the growing popularity of supporting local agriculture and in lessening environmental impact while adding convenience.

“By having us bring the bag from the farm directly to your office [we] save both parties a trip to the grocery store,” she says.

Local produce delivery programs are starting to pop up in larger markets across the nation like Field Goods in New York and FarmBox in San Francisco, Calif. Williams hopes the merger between corporate offices and small farm productions continues to grow and sees the market as a fresh opportunity for controlled environment agriculture.

“There’s a lot of opportunity for greenhouse growers out there,” says Williams. “I hope more people are game to get in the business and more farmers do more crop extension.”

The fast-paced adidas shoe commercial released in January 2016 opens with a dismal, dystopian, post-apocalyptic scene complete with burning cars, a stray dog, a semi-destroyed forest and people walking through it all. It continues on to show a wide array of examples of popular culture that are criticized in the media as being bad or “conformist,” such as taking photos using selfie sticks, undergoing plastic surgery, eating junk food, preferring virtual reality to the real thing and using cell phones excessively. In every scene, a group of people wearing adidas gear walks through the dark scenes seemingly “overcoming it,” while a singer proclaims “Your future is not mine.” At the end, the group of nonconformists arrives at a brightly lit tunnel with the word “future” at the end, presumably a place where these negative things don’t exist.

I stopped and re-watched the commercial several times because of one very brief, yet poignant, scene that I couldn’t (and can’t) wrap my head around. At about 15 seconds in, we get a close-up of a person in a yellow hazardous materials suit, boots and full gas mask. As the camera pans out, we see two people walking through a greenhouse that is tinged pink with the light of LEDs and foggy with the clouds of some sort of insinuated “chemicals” that the men in yellow suits are liberally spraying all over the greenhouse plants. Overall, it seems like every attempt was made to make greenhouse production look as unnatural, futuristic and harmful as possible — an environment that people should avoid.

Misconceptions like these run rampant in the industry, and commercials like this one certainly don’t help the cause. With some consumers associating “greenhouse-grown” with GMOs, chemicals and “unnatural” growing processes, growers have their work cut out for them to show that their produce is just as good as field-grown crops, or perhaps even better. Some growers we’ve talked to have already made an effort to educate consumers through classes or outreach programs at grocery stores or by addressing consumer questions about the topic in a FAQ on their website.

But are we doing enough as an industry to dispel these negative assumptions about produce grown in controlled environments, whether it’s in a greenhouse or a plant factory? Please share your thoughts with me at kvarga@gie.net.

kvarga@gie.net | (216) 393-0290

Twitter: @Karen_GIE