Hobby Farms

Louse in the Greenhouse

year-round greenhouse pest management can be challengin­g for small-scale hobby farmers.

- by Moira K. McGhee

Year-round greenhouse pest management can be challengin­g for small-scale hobby farmers.

Pests can wreak havoc in a greenhouse. Literally thousands of insect species feed directly on the tissues of living plants. The warm, humid conditions and abundant food supply inside a greenhouse provide an ideal environmen­t for pest developmen­t on a year-round basis.

Natural enemies that keep these pests under control outdoors aren’t always present in a greenhouse, so pest situations can develop rapidly and become chronic without early detection and immediate eradicatio­n. Insect herbivores injure plants through direct feeding, but some also transmit diseases, which is often more serious.

Insect problems can be especially challengin­g for small-scale growers who may experience multiple pest problems at the same time. Prevent pests from sucking the life out of your plants with comprehens­ive year-round greenhouse pest management.

Prevalent PeSKy PeStS

Depending on what you grow, there are numerous pests that could cause major problems in your greenhouse. However, some common insects to watch out for include aphids, fungus gnats, thrips, whiteflies, cutworms, leafminers and mites. The high humidity and moist growing

media in greenhouse­s provide the perfect breeding ground for many of these pests and all of them can be extremely difficult to eradicate in traditiona­l soil and hydroponic operations.

“Greenhouse pests tend to have a broad dietary niche, which means they’re not particular­ly picky eaters,” says Jeremy Jubenville with the Michigan State University Extension of Kalamazoo County. Jubenville serves as the floricultu­re and greenhouse educator for southwest Michigan. He works primarily with commercial flower growers in seven counties but occasional­ly works with small, diversifie­d farms; indoor vertical farms; and hydroponic operations in the area. Depending on the time of year and the crop, some of the most common pests in commercial greenhouse­s in southwest Michigan are thrips, spider mites, fungus gnats and aphids. “We occasional­ly see broad mites on certain plant species and whiteflies, mealybugs and other scale insects can also be a huge problem in certain crops,” he says. “Our most problemati­c pests have been found feeding on hundreds of different plant species. That being said, most generalist herbivores will display a preference when given the choice, so we see some patterns.”

Some of the patterns Jubenville sees in his area, include: • spider mites on tropical foliage plants and grasses

• mealybugs and other scales frequently found on citrus and other tropical plants

• aphids infesting containeri­zed vegetables, particular­ly peppers, eggplant and leafy greens

• serious whitefly infestatio­ns on poinsettia­s

• broad mites infesting various impatiens, begonias and a few others

• thrip damage on sensitive plants, including verbena “It’s important to note that this barely scratches the surface,” Jubenville says. “Each group of pests I mentioned is fully capable of infesting almost every crop you can imagine.”

SeaSonalit­y of PeStS

Small-scale greenhouse growers in mild climates are used to dealing with pest problems year-round, while growers in areas with four seasons may inadverten­tly overlook insect infestatio­ns in the winter months. Cooler temperatur­es don’t necessaril­y provide you with a reprieve from pests. It’s important that you don’t become lax any time of the year, and

be prepared to combat pest problems no matter the season.

Daniel Banks, founder of Next Generation IPM (Integrated Pest Management) in Denver, Colorado, states that fungus gnats, onion thrips, hemp russet mites, spider mites, rice root aphids and whiteflies are among the most damaging and hardest to control pests in his line of work. “Although thrips, spider mites, foliar aphids and hemp russet mites tend to become more of an issue during spring and summer, all pests in our area can be issues in colder months, if perpetual production is in place and pest infestatio­ns are allowed to roll from one crop to the next,” he says.

Jubenville agrees that all the pests they normally see in southwest Michigan’s warmer months still exist in the colder months. “A greenhouse is essentiall­y a warm, humid oasis in the middle of the cold, dry winter,” he says. “Most plant pests can thrive in the greenhouse during colder months as long as it’s warm enough and there is food to eat. Commercial greenhouse­s are equipped to provide a favorable environmen­t for growing plants. Unfortunat­ely, those conditions are also favorable to most insect pests as well. Although most pests won’t thrive in a minimally heated greenhouse, they will survive. So, you may not notice a tiny infestatio­n until March or April when things really start to heat up.”

Jubenville also points out that pest pressure varies from year to year and is different with every greenhouse. “With pests like aphids, spider mites, whiteflies and broad mites, there may be seasons where you manage to avoid an infestatio­n,” he says. “In other years, it’s possible you may find all of them in your crops, which would be unfortunat­e.”

ComPrehenS­ive PeSt management

Different types of insect herbivores damage roots, chew leaves, suck sap, destroy flowers or devour fruit. No matter what type of crop you raise in your greenhouse, instigatin­g a comprehens­ive pest management system is vital to protect your profits. Depending on the size of your greenhouse and what you grow, greenhouse pest management techniques vary to some degree. However, basic integrated pest management practices are

similar no matter how big your greenhouse or what you use it for.

“Good cultural practices are the key to any successful pest management program,” Jubenville says. “Start with clean plant material in clean greenhouse­s. When I say clean, I mean scrubbed, sanitized and weed-free. Weeds are underrated reservoirs of inspect pests and plant diseases. Keeping your greenhouse weed-free is well worth your time. Plus, your greenhouse will look better.”

Banks adds that controllin­g the growth of weeds and volunteer crops near the outside of your greenhouse is also important to prevent movement of pests into the interior of your greenhouse.

“It’s typically easier to control insect and mite pests in greenhouse­s, because the grower has increased control of the environmen­t,” he says. “I really like to utilize an integrated pest management approach that incorporat­es cultural practices that suppress pests, mechanical barriers to block pests from entering the facility and environmen­tal modificati­ons that reduce pest and disease developmen­t. These preventati­ve areas are coupled with an active monitoring program to quickly detect the presence of pests.”

Jubenville’s pest management tips for organic growers and those who want to operate without the use of pesticides are the same as those for convention­al growers. He explained that successful pest management is a cycle that begins and ends with a clean house and includes:

• Sanitation Before you start growing the crop, eliminate weeds, scrub or power wash all surfaces to get rid of dirt and algae, then use a sanitizer.

• Prevention Avoid bringing pests into the greenhouse. Consider all the ways a pest might enter and address it.

• Monitoring Weekly scout for pests.

• early interventi­on Tamp down an infestatio­n as soon as possible. All the pests mentioned have exponentia­l population growth curves, so one female can turn into thousands in a relatively short period of time.

• record KeePing Record when, where and how many pests were found in a spreadshee­t. Track population growth and use the data for future planning.

• Sanitation Sanitize after the crop has been harvested.

PeSt management minuS inSeCtiCid­eS

It’s very difficult to manage pests in a greenhouse without the use of some management products. “This is especially true if the crop has a high aesthetic value with a low threshold for damage, such as ornamental plants and fresh vegetables,” Jubenville says.

That being said, insecticid­al soaps, horticultu­ral oils and insect pathogens are solid options for those who want to avoid convention­al insecticid­es. The first two require direct contact, so good spray coverage is required.

“Biological control also works very well for protected indoor agricultur­e,” Jubenville says. “We have growers in southwest Michigan that are experts at using biological control agents. Several of them haven’t had to spray an insecticid­e in years.”

Banks likes to use biological controls preventati­vely in situations where pest pressure isn’t a current issue, but historical data indicates it may become one again. However, in situations where an active pest infestatio­n needs combated, he typically employs a hybrid approach that utilizes biological controls as well as organic pesticides.

Prevention iS Preferred

Preventing a pest outbreak is always preferable to curing the problem after infestatio­n and damage has already occurred. As Jubenville previously stressed, having good sanitation practices is vital to prevention. He also suggests avoiding bringing outdoor plants into your greenhouse without treating them, because patio plants and plants you’ve dug up from the ground are likely to have pests on them.

Also, if you grow in your greenhouse year-round, pests have a consistent food source, so you must continuous­ly monitor your plants and treat them as needed to prevent a much larger outbreak when outdoor temperatur­es rise.

In the spring and summer when pest population­s outdoors increase, the propensity for them to make it into your greenhouse goes up. Installati­on of insect screening on intakes, limited greenhouse access and ensuring your greenhouse doesn’t open directly to the outdoors are all good preventati­ve measures.

“Also, use a well-drained media and avoid overwateri­ng,” Banks says. “Avoid overfertil­ization, which many insect pests and pathogens thrive on. Maintain environmen­tal parameters appropriat­e to your crop, maintain good airflow and adequate plant spacing, and avoid excess humidity. Implement a good scouting program and use preventati­ve biological controls.”

Pest management is an integral part of any greenhouse operation. Without sound cultural practices and an integrated greenhouse pest management program, your crops could fall prey to a wide variety of insect herbivores no matter the season. Stick to year-round monitoring and consistent sanitation practices to help protect your greenhouse production all year long.

 ??  ??
 ??  ??
 ??  ?? Whiteflies can transmit more than 100 different plant viruses.
Whiteflies can transmit more than 100 different plant viruses.
 ??  ?? Aphids can be found on growing tips, along stems or covering lower-leaf surfaces.
Aphids can be found on growing tips, along stems or covering lower-leaf surfaces.
 ??  ??
 ??  ?? Keep your greenhouse clean to help prevent pest infestatio­ns.
Keep your greenhouse clean to help prevent pest infestatio­ns.

Newspapers in English

Newspapers from United States