Description of the Pest
Adult crane flies emerge from the soil beneath turfgrass, pastures and other grassy areas in late summer and fall. The adults have very long legs and resemble large mosquitoes. Females mate and lay eggs in grass within 24 hours of emerging. Eggs hatch into small, brown, wormlike larvae that have very tough skin and are commonly referred to as "leatherjackets". The leatherjackets feed on the roots and crowns of clover and grass plants during the fall. They spend the winter as larvae in the soil; when the weather warms in spring, they resume feeding. During the day larvae mostly stay underground, but on damp, warm nights they come to the surface to feed on the aboveground parts of many plants. When mature, the larvae are about about 1 to 1½ inch long. Around mid-May they enter a nonfeeding pupal stage and remain just below the soil surface. In late summer, pupae wriggle to the surface and the adults emerge. There is one generation a year.
In California, crane flies have primarily been found at damaging levels in the Humboldt and Del Norte counties and do not appear to be a problem on turfgrass in warmer, inland areas. All cool-season turfgrass species appear to be susceptible.
The larvae are the damaging stage of this pest. They feed on the roots, crowns, and aboveground portions of grass plants. Healthy, vigorous turfgrass can withstand low to moderate populations. Damage often becomes noticeable in March and April and appears as dying patches of turfgrass. Weeds may invade areas of dying turfgrass. Although the adults resemble mosquitoes, they do not bite or sting; it is believed that they feed primarily on plant nectar. Populations of crane fly larvae have been reduced by as much as 50% during the winter months and between March and May as a result of predators such as birds and predaceous ground beetles and other natural causes.
A vigorously growing, well-maintained turfgrass can easily recover from the feeding of crane fly larvae, even when the populations are fairly high. Monitor for crane fly larvae if the turfgrass is exhibiting areas of poor growth. Adequate nitrogen fertilizer is essential.
Drenches with the nematode Steinernema feltiae may give up to 50% reduction if properly applied.
Proper fertilization and irrigation are important factors in determining how much feeding by crane fly larvae the turfgrass can tolerate. Well-maintained turfgrass has been observed to withstand populations of crane fly larvae that averaged 40 per square foot, whereas unthrifty turfgrass may exhibit damage with as few as 15 larvae per square foot. Application of nitrogen in the spring may reduce damage. Provide better drainage for chronically wet areas and reduce irrigation. Craneflies thrive in wet soils.
Growing turfgrass species that require full sun in shady areas can reduce plant vigor and promote survival of crane fly larvae. In areas of low sun, consider a turfgrass species that prefers shade or a groundcover.
Remove excess thatch; it provides an ideal habitat for crane fly larvae, which feed mostly just below the thatch. Aerify the soil to stimulate root development and improve the movement of water and nutrients into the soil. Reseed bare areas of turfgrass so that weeds do not invade.
Monitoring and Treatment Decisions
Monitor crane fly larvae in spring when the weather has warmed, generally in March. Samples can either be taken with a 4-inch diameter cup cutter or by digging up a 6" by 6" area of turfgrass about 1 to 2 inches deep. Larvae will usually be found at the base of the vegetative layer (thatch) or in the soil just beneath the plants. Pull apart the samples and count the number of crane fly larvae. If a 4-inch diameter cup cutter is used, multiply the number of larvae in each core by 11.5 to get the number of larvae per square foot. If a 6" X 6" area is sampled, multiply the number of larvae by 4 to get the number of larvae per square foot. Sample three or four locations and determine the average number of larvae per square foot. If damaged areas of turfgrass are sampled, take the sample from the edge of damaged area and not from bare patches, where the larvae would no longer be present. Continue monitoring through April, if no damage is observed by then, no further action is needed.
Research has not been conducted in California on treatment thresholds, but in Washington, the treatment threshold is 25 to 50 larvae per square foot.
|Common name||Amount per 1000 sq ft**||Ag Use
|(Example trade name)||(hours)||(hours)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Acelepryn)||Label rates||4||Until dry|
|(Acelepryn G)||Label rates||4||After application complete|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|COMMENTS: Applications should be made when overwintering adults are first observed, usually in April or May. Higher rates may be necessary when this window has passed.|
|(Arena 50 WDG)||Label rates||12||Until dry|
|(Arena 0.25 G)||Label rates||12||When dust has settled|
|MODE-OF-ACTION GROUP NUMBER1: 4A|
|COMMENTS: Optimum control will be achieved when applications are made before egg hatch followed by sufficient irrigation or rainfall. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|C.||STEINERNEMA FELTIAE||25 million||NA||NA|
|COMMENTS: Store nematodes properly before use as directed. Apply to warm, moist, but not soggy soil. Several irrigations may be needed during 2 weeks after application to keep soil moist. Apply during the coolest time of day in hot areas.|
|(Sevin SL)||Label rates||12||Until dry|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Water or irrigate turf soon after treatment. Nontarget effects likely on other soil-dwelling organisms. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.|
|**||Apply in 25 gal water/1000 sq ft|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.|
|—||Indicates use is not listed on label.|