Jan 9, 2019
Insect control plan boosts greenhouse IPM

A control plan is key to managing insect pests in the greenhouse. “You plan ahead for something that could happen so you’re ready to go if something does happen,” said Luis Canas, associate professor in entomology at Ohio State University.

Canas is based at the Ohio Agricultural and Research Development Center (OARDC) at Wooster, Ohio.

A plan is especially important if you have the same problems every year. “You can map the flow of work to identify critical, potential risks,” Canas said. “If you can map the flow of work in your facility, you can map where the outbreaks may be possible.”

A map of outbreaks can help you identify pest harboring places and entrances that need more attention. It can tell you how consistently you’re starting with clean plants and if your sterilization plan needs improvement. “Pest prevention is key in any system,” Canas said.

Employees are a key source of information. They’re working with the plants every day and with proper training in pest identification will probably see outbreaks before anyone else. “It’s not enough to know it’s an aphid,” Canas said. “You must know exactly what type of aphid it is.”

Sticky cards can identify pest presence, movement and areas of concentration, and are a simple tool for workers to use.

Yellow cards are the standard although blue cards may be more attractive to thrips. “If thrips are all you have and see, blue is OK,” Canas said. Other colors may be more effective for other insects.

A good rule-of-thumb for minimum density is one sticky card per 1,000 square feet of greenhouse, although you’ll want more cards near doors, vents and insect-sensitive plants.

Inspect the cards regularly. “Have someone come in and check them weekly,” Canas said. “If you deploy them, you need to look at them.”

Sticky card use must be combined with scouting. “Sticky cards don’t tell you how many insects are in an area,” Canas said, “but sticky cards can tell you what pests you have and if their numbers are going up or down.”

“Some insects can’t be caught on sticky cards,” he said. “Aphids only develop wings after the population has exploded and the first host is senescing (falling apart due to age). If you’re catching aphids on your sticky card, you already have a big outbreak.”

Be sure to include the information collected from sticky cards into next year’s pest control plan.

Your pest control plan should also include your planned, insecticide rotation to prevent resistance.

“No insecticide will kill 100 percent of the insects you find,” Canas said. “If one out of 100 survive, that one is resistant and so are its offspring.”

Resistance prevention involves alternating insecticides with different modes of action (MoA). Guidance on MoA rotation is available from the Insecticide Resistance Action Committee (IRAC) at www.irac-online.org.

IRAC classifies insecticides into groups, such as products that act on insect nerves and muscles, or products that interfere with insect respiration. Each insecticide within a group is assigned its own MoA Group number.

Carbamates and pyrethroids, for example, both act on insect nerves and muscles, but with different MoAs. This means they’re assigned different MoA Group numbers with carbamates being Group 1 and pyrethroids Group 3.

Rotations to prevent resistance should be based on the MoA Group number. The IRAC MoA Group number is on the product label.

“We say a control plan should have at least four modes of action groups over the season, but that’s not always possible,” Canas said. Tank mixes combine MoA groups – and there may be situations where they have to be used, but tank mixes can accelerate the onset of resistance.

“There are many, many types of rotation,” he said. Many growers use oils or soaps to smother insects and plan this into their rotation. Some will use oils or soaps and then release predators.

Biological controls are increasingly becoming the control of choice in controlled environments (CE), but they must be used in a timely manner. “You want to identify problems early when using biologicals,” Canas said. “Biologicals need to be used as a prevention tool.”

“The industry has shifted,” he said. “It’s been able to use biologicals to manage pests more than to treat them. The CE industry has changed.”

The purpose of putting all of this information into a control plan is to make your decisions easier during the growing season. “How often have you had a problem with aphids – every year?” Canas asked. “Then have a plan to control them. Have a plan.”

– Dean Peterson, VGN Correspondent

The purpose of an insect control plan is to make your decisions easier during the growing season, said Luis Canas, associate professor in entomology at Ohio State University. Canas is based at the Ohio Agricultural and Research Development Center at Wooster, Ohio. Photo: Dean Peterson

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