Grass seed-Crane fly

European crane fly (Tipula paludosa)
Common or marsh crane fly (Tipula oleracea)

Pest description and crop damage Adults are large (wing span of 1 to 1.5 inches), grayish brown, and resemble large, long-legged mosquitoes. They do not bite! The wings of these pest species are long, slightly milky-brown along the fore-edges, and folded in roof-like when the adults are at rest.

Commonly referred to as "mosquito hawks," they do not eat mosquitoes; in fact, they probably feed only on a little free moisture during their short existence (3 to 7 days).

Mature larvae are 1 to 1.5 inches long, legless, and earthy gray. The body is cylindrical, squishy, but very tough and resilient (the larvae are called "leatherjackets"). The body extends and retracts considerably, and the primitive head can retract, giving the larva a tightly packed and pudgy appearance. Eggs are black, narrow, rigid, and about 0.03 inch long.

The larvae of these two pest species feed on many plant species, including grasses, clovers, mint crops, root vegetables, and probably even decaying matter. As larvae mature, they come to the soil surface at night and feed above ground on crowns of grasses. They have been seen to clip stems of peppermint.

Most larval infestations in grasses have been in irrigated turf-golf courses, lawns, parkways. However, large numbers of larvae occasionally are in perennial ryegrass and other grass seed crops when there is heavy rainfall and excessive soil moisture. In grass seed crops, larval heavy feeding has been associated with stand loss. However, usually other stresses are present as well. Full effects of larval feeding on grass seed crops have yet to be described.

Be aware that adults of many crane fly species often are in grass seed fields, particularly in winter and spring. Most are not harmful and have emerged from larvae that lived in waterways in and around the fields. With the exception of these two new pests, Oregon crane flies are aquatic or semiaquatic, do not feed on living plants, and are not pests of plants.

Biology and life history The European crane fly, T. paludosa, deposits eggs randomly on moist soil, grasses, clovers, and cover crops by dropping them in flight or when walking over these areas. An adult female produces 300 to 400 eggs, which hatch in 11 to 15 days. Larvae enter the soil and feed on humus, vegetable waste that is decomposing, and crowns or roots of plants through late April and early May. Young larvae tend to remain in the soil day and night and are highly resistant to cold. In spring, the larger larvae come to the soil surface at night and feed on aerial parts of plants. Larvae pupate in the soil (late June, July, early August). Adults emerge in late August and September. Tipula paludosa has one generation per year. Tipula oleracea may have two generations per year with flight activity in the spring and again in the fall, coincident with T. paludosa.

Scouting and thresholds The extent to which these crane fly larvae damage grass seed crops has not been researched adequately. In turf grasses that are of normal vigor, well fertilized and watered, and without other stresses, more than 20 crane fly larvae per sq ft have not produced aesthetic damage or stand loss. However, larval populations approaching 5-10 per sq ft in some grass seed crops are thought to damage grasses that are weakened or subject to other stresses.

Crane fly larvae can at times be flushed from moist soils by pouring a caustic solution over the soil surface and allowing it to penetrate to where larvae are. Soap solutions, chlorpyrifos (Lorsban) insecticide, and weak concentrations of pyrethroid insecticides cause the larvae to wiggle to the surface soon after application.

Soil cores 3 inches deep are usually sufficient to detect larvae in root material. Pick apart roots and soil over a series of screens and observe larvae that collect on the screens. Berlese funnels also are used to process soil cores, but this can take a substantial amount of time (days) to process.

Management-chemical control

  • azadirachtin/pyrethrins (Azera) at 1 to 3.5 pints/A. OMRI listed for organic production.
  • bifenthrin (Brigade 2EC and WSB) at 0.1 lb ai/A). Apply in early fall and/or spring when larvae are active. Best results are achieved with 25 to 40 gallons of spray solution per acre followed by irrigation or rainfall. Maximum amount allowed is 0.2 lb ai/A per season but no more than once every 14 days. PHI 30 days prior to harvest for forage, hay and seed.
  • carbaryl (e.g., Sevin XLR Plus, 4F) at 1.0 to 1.5 lb ai/A product. PHI 14 days. REI 12 hr. Up to two applications per year, but not more than once every 14 days. Do not exceed 3 lb ai/A per season.
  • chlorantraniliprole (Vantacor) at 0.066 to 0.098 lb ai/A (1.7 to 2.5 fl oz/A). PHI is 0 days. REI 4 hr.
  • lambda-cyhalothrin (Warrior) at 0.02 to 0.03 lb ai/A. PHI 0 days for grazing and forage, 7 days for straw and seed crop. REI 24 hr.
  • lambda-cyhalothrin/chlorantraniliprole (Besiege) at 6.0 to 10.0 fl oz/A. PHI 0 days for grazing and cut for forage, 7 days for straw and seed crop. REI 24 hr. Do not exceed a total of 27.0 fl oz of Besiege or 0.09 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per year.
  • zeta-cypermethrin (Deadlock G) at 10 lb/A. Distribute granules evenly in the furrow at planting. Only one application is allowed per season. Maximum amount that can be applied is 10 lb/A per season. No rotation crops can be planted within 30 days of the last application. REI 12 hr.