Experts share how to properly identify and combat crane flies

August 23, 2023 -  By
Crane flies spend most of their life cycle as larvae, leaving plenty of time to cause turf damage. (Photo: Ben MCgraw Ph.D.)

Crane flies spend most of their life cycle as larvae, leaving plenty of time to cause turf damage. (Photo: Ben MCgraw Ph.D.)

Though there are more than 500 native species of crane flies in North America, only the European and marsh crane flies cause turf damage.

To properly identify crane flies, lawn care operators should scout and send samples or images to a turf entomologist. The damage crane flies cause is similar to what LCOs find with other pests and environmental factors, says Jesse Benelli, Ph.D., green solutions team specialist with Envu.

Jesse Benelli

Jesse Benelli

“Scouting is important because thinning of the turf will be the first symptom of a crane fly presence,” Benelli says. “Stick a knife in the ground to check for crane fly larvae.”

Once identified, cultural practices play an important role in controlling them, Benelli says. Operators should restrict irrigation as much as possible if there’s an issue with crane flies.

“Larvae are very prone to desiccation. It’s OK to let things dry out and turn down the irrigation system,” he says. “If the soil is too dry, it will push down the population base.”

When LCOs need chemical applications, timing is everything, Benelli says. The majority of crane flies emerge during the fall, but the marsh crane fly also has a generation that comes out in the spring.

“If you time it just right, you can use a contact insecticide pyrethroid, but that application would have to be made after the eggs hatch and before larvae burrow down in the soil,” he says.

Early control

LCOs can find European crane fly in the Pacific Northwest, Midwest and states along the East Coast, says Chris Williamson, Ph.D., research scientist with PBI-Gordon. While their feeding activity can be confused with other pests, it’s easy to identify crane flies, which resemble large mosquitoes as adults.

Chris Williamson, Ph.D.

Chris Williamson, Ph.D.

They have a leathery appearance as larvae, and it’s in that stage where problems can arise if there’s a dense population in the turf.

“In the spring, the larva stage can come and cause damage to turf by feeding on the root and crown,” Williamson says. “You want to have a management plan in place to treat for the young larvae. The bigger they are, the more difficult they are to control.”

Mitigating the amount of moisture on properties can help control the pests, so can fall applications of synthetic pyrethroid insecticides.

“Insecticide choices are much greater for fall applications than what we could use in spring,” Williamson says.

He also recommends making treatments later in the day or early evening because the larvae are largely nocturnal and feed at night. That helps prevent the product from being exposed to sunlight or other elements to maximize its efficacy.

Limit moisture

Lisa Beirn

Lisa Beirn

Crane flies prefer moist locations to lay their eggs, so operators should avoid overwatering, reduce thatch and improve drainage, says Lisa Beirn, Ph.D., technical manager with Syngenta.

“In addition, maintaining proper fertility and mowing at an appropriate height will promote healthy turf that can better withstand stress and recover more quickly should feeding damage occur,” she says.

When chemical control is necessary, preventive applications are key and LCOs should make them during the fall when adults lay eggs or when the larvae are small and near the surface.

“If feeding damage is observed in the spring, curative applications can be made but control can be more difficult at that time,” Beirn says.

If there has been crane fly damage on a property in the past, the pest will likely be an issue in future seasons, as well.

“Crane flies tend to return to the same areas to lay their eggs each year, so continue monitoring sites with a history of damage each year,” Beirn says.

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