Invasive Crane Flies

in the Northeast

To detect the presence of invasive crane flies, the pupal cases can be monitored on tees and greens where they protrude from the low-mown turf.  At peak emergence times in the spring (T. oleracea) or fall (both species), adults may become very abundant and noticeable as they flit about low in the grass.  They may also congregate during the day on the sides of buildings, sliding doors, window screens and fences.  Because adults lay eggs so soon after emergence, at least for T. paludosa, they do not move far.  Therefore, sites with abundant adults, larvae or pupal cases should be monitored as an indication of sites where eggs of the next generation are likely to be laid.  If a European crane fly infestation is suspected, send adults, larvae or pupal cases to a specialist for proper identification. While it is not yet possible to reliably distinguish larvae and pupae of the two invasive species, they can be differentiated from native crane fly species, and observations on the abundance of those life stages could also help diagnose the problem if adults cannot be collected.  Up to now, there are no accounts of native crane flies causing injury to turfgrass.

If signs of insect activity and turfgrass injury suggest leatherjackets, core sampling is the best way to detect and sample larvae.  Take samples with a cup cutter and rip apart the core to look for larvae.  Depending on the insect’s life cycle and field conditions, the larvae are best sought in a core by both searching from the soil up to the base of the roots and thatch layer, and by searching down from the grass where larvae can be concealed in the upper layer of the thatch.  This is the best way to make accurate population counts.  Although disclosing solutions (such as dish soap or dilute pyrethroid solutions) have been suggested as an alternative, they may not work well; when these irritants are poured onto the turf, larvae are supposed to be driven to the surface where they can be seen.  Even if this method were to expose leatherjackets, it would greatly underestimate population densities.  Adults are best captured with a sweep net, but they can also be seen flitting about in grassy areas or perching on nearby vegetation.