Managing Crane Fly Damage
Welcome, Turf Guardians, to the perennial battle against crane fly infestations. To the uninitiated, this war might seem as tranquil as a golf course on a windless day. But to the trained eye of a turf manager, the sight of crane fly damage can cause a flutter of concern. With these delicate yet devastating insects, prevention and management are key to maintaining the splendor of your turf. These large, mosquito-like insects can be found in the majority of the Northern United States and can be a catastrophically damaging pest to any turf area. Below are some important cultural practices that you can use to identify, anticipate and mitigate the effects of this pest.
Understanding Crane Flies: More Than Just a Flying Nuisance
Crane flies are often mistaken for large mosquitoes due to their long, spindly legs and fragile appearance. Unlike their pesky lookalikes, adult crane flies are harmless to humans, but their offspring—leatherjacket larvae—are the silent destroyers of lawns and sports fields alike. These translucent, legless larvae chew through the turf's root system, leaving swaths of grass wilted and vulnerable.
The adult crane flies, in their fluttering dance, lay eggs in the moist soil, typically in late summer or early fall, signaling the silent but insidious crop of larvae waiting to rise in the spring. Given that they live in moist environments, sports fields and golf courses are appealing breeding grounds, making proactive management a requisite for a healthy turf.
History
As the year dwindles down, we feast through the holidays, and the European crane fly (Tipula paludosa) larvae begin engorging themselves as well. The European crane fly is a common pest in the northern United States, originating from western Europe. It became a pest in North America in 1952 when it was first introduced to Newfoundland, Canada; then became a prevalent problem when it hit the western shore on British Columbia, Canada. From the west coast of Canada, the European cranefly headed south, invading the majority of the northern United States.
Identifying Crane Fly Damage: The Telltale Signs
Detecting crane fly damage early is vital. But what should you look for?
- Thinning Grass: Affected areas often show a patchy reduction in turf density as the larvae feed underground.
- Increased Weed Presence: With the turf's health declining, opportunistic weeds can take root, exacerbating the visual blight.
- Brown Patches and Dead Spots: Where larvae activity is high, brown, dead-looking areas will emerge as the grass succumbs to root damage.
Damage can be seen in the turf stand as the living turfgrass begins to die in patches. Bare soil is exposed as larval feasting continues in the winter and spring, while larvae may be visible from the surface along with their castings. If you are unsure crane fly larvae are the culprits of patchy senescence, take a sod cutting by exposing the top 1-2 inches of soil and grass from a 1 foot by 1 foot area using a shovel, as seen in the picture on the bottom right. If there are more than 25-50 larvae in this sample, populations may be above an acceptable threshold and would require control.
Preventing Crane Fly Infestations Before They Hatch
Prevention is the best strategy for managing crane flies and protecting your turf from their voracious appetites. Here are several methods to keep your turf impenetrable to these soil-bound adversaries.
Proper Turf Maintenance
A strong, healthy turf is less prone to succumbing to pests. Regular aeration, appropriate fertilization, and the promotion of beneficial microbial activity in the soil can bolster the grass against potential damage. A diverse and robust turf ecosystem creates a formidable defense against pests like crane fly larvae.
Reducing Moisture Levels
Since crane flies prefer laying their eggs in damp soil, controlling moisture is an effective deterrent. Ensure proper drainage, regulate irrigation, and improve air circulation to keep the soil on the drier side, especially during the egg-laying season.
Encourage Natural Predators
Several creatures relish a meal of crane fly larvae, including birds and ground beetles. Improving the habitat for these allies, like reducing pesticide use and providing shelter and food sources, can help maintain a natural balance.
Development
The awkward, mosquito-like adults begin to make their appearance in the late summer, bumbling through the air and clinging onto walls. While the adult’s life stage does not cause the greatest damage to the turf, their emergence from the soil causes castings similar to that of earthworms, and leaves exposed bare soil that welcomes weeds and other pests. Within 24 hours of emerging, the females mate and lay dark, jellybean-like eggs in the turfgrass, or sometimes off-crop in the nearby habitat where constant moisture can be maintained. Eggs incubate for 11 to 15 days and then hatch into their first of 4 larval instars. The larval stage is where the majority of damage is caused to the turfgrass. These leathery larvae eat away at the crowns and roots of turfgrass. In the spring, when temperatures begin to rise again, the crane fly larvae surface in the damp evenings to feed on the turfgrass blades, while continuing to feed underground in the day.
Managing Crane Fly Larvae: When Prevention is No Longer Possible
The Pacific Northwest Pest Management Handbook suggests that irrigation should be discontinued around Labor Day to mitigate the larval populations, if fall seeding is not occurring. However, depending on the severity of the historical populations of crane flies, this tactic may not ensure adequate control, and pesticides may be required. Caution should be exercised when applying insecticides, following the label recommendation, optimal population thresholds, and timed application which should not coincide with pollinator activity.
Post-Infestation Recovery and Turf Restoration
After the battle is won, the focus shifts to recovery and restoration. The turf needs to be nurtured back to health, often requiring reseeding or even resodding in severe cases. Maintaining a vigilant eye for signs of re-infestation and promptly addressing them is crucial in the post-infestation phase.
Conclusion and Recommendations for Long-Term Management
The lifecycle of crane flies offers a template for year-round management. By implementing prevention strategies, engaging in vigilant monitoring, and tailoring interventions as needed, you can keep the magnificent green expanses under your care free from the legacy of their uninvited guests. With a combination of knowledge, ongoing maintenance, and the support of cutting-edge solutions, the turf under your stewardship can flourish, untroubled by the menace of crane fly damage. Remember, the war against pests is not waged in a day; it's a continual campaign. Prepare for it, plan for it, and persevere. Your tireless efforts will be reflected in the beauty of the turf you protect.
