Intruder alert

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.