IPM CONTROL OPTIONS FOR KEY TURFGRASS INSECT PESTS

Mole Crickets

 

Distribution

The shortwinged, Southern and tawny mole crickets occur in the South Atlantic and Gulf Coast regions, from Virginia to Texas. The shortwinged species is restricted to coastal Florida and Georgia. The southern is the most wide spread of the three.

The northern species is found throughout the eastern half of the U.S.

 

Life History

The Southern and tawny are very similar in life cycle, habitats, and destructive behavior. They will be considered together. Nymphs and adults migrate deep into the soil during cool weather, and pass the winter in the soil. In spring and early summer, eggs are laid in cells which the females construct in the soil. About 35 eggs are laid in each cell. These hatch in 10-40 days, depending on ambient temperatures. Nymphs grow rapidly, most becomig adults before fall. Those emerging from eggs laid late in the season will become adults in the spring of the following year.

 

Hosts/Habitat

Nymphs and adults of both the southern and tauny species feed on various warm season grasses; Bermuda and bahia grass appear to be the major hosts. Mole crickets also feed on garden vegetables, tobacco, peanuts, and strawberries. Underground stems, roots, tubers, and fruits touching the ground may also be damaged.

Mole crickets are rarely found in heavy soils, they prefer sandy to sandy loam types. Regardless of texture moderate to high soil moisture is a prerequisite in maintaining the open tunnel structures. Nightly tunneling ranges from 5-20 ft. Both nymphs and adults hide in this tunnel system by day and emerge at night to feed on plants, roots, organic matter and other arthropods. They can be cannibalistic particularly the southern species.

 

Damage/threshold/sampling

Immatures and adults burrow in loose soil, feed on grass roots, and cause the turf to dry out. Damage is usually localized in irregular areas, and can be severe in newly-planted turf. Infested areas may feel "fluffy" underfoot due to the tunnels under the thatch. Suspect turf can be visually inspected for the presence of entrance holes (1/2 - 1" in diameter) in the soil or thatch layer. A quantitative estimate of mole cricket populations is obtained using the soap flush technique. A solution of 1-2 ounces of liquid dishwashing soap in 2 gallons of water is sprinkled over a marked 4 ft2 area of turf. The soap irritates the insects, driving them to the surface. All mole crickets coming to the surface in the three minute period following treatment are counted (and the total is divided by four to convert to number per square foot) (Short et al. 1982). Short et al. (1982) determined the economic threshold for this pest at 2 per 0.1 m2 for bahia grass lawns in Orlando, Florida.

Other thresholds are based on 4 sq. ft. sample area using either a soap or pyrethrin irritant flush. Insecticides are usually recommended after the emergence of 7 mole crickets within

3 min. Several researchers noted examples of severe damage to golf tees caused by mole cricket population > 1 per sq. ft.

Another source of aesthetic damage is the mound of soil that accumulates at the tunnel entrance. These small mounds produced by the tunneling nymphs and adults will regardless of population levels cause problems on golf course greens and tees. There presence interferes with play and mowing activities.

 

Biological Control

Several researchers report that the fungi Metarrhizium anisopliae, the green disease (metch) and Sorosporella uvella (Kass) the red disease will infect mole crickets. However these natural occurring fungal disease are not consistent from year to year. Several commercial products with the Metanhizium fungi are available outside the U.S. but similar products are expected to be registered here before 1994.

The most promising biological agent to date is the parasitic nematode, Steinernema scapterisa. Preliminary research by Parkman and Frank at University of Florida demonstrated that sound traps using 2 Mans-type emitters, each set for a single species can be used to attract and expose mole crickets to this nematode. Early studies also determined that this nematode could be released once and persist for several years in pastures. Commercial products with this unique mole cricket nematode should be available after 1993.

Natural occurring Parasitism and Predation is limited, but the fire ant, ground beetles, spiders and the mole crickets themselves do help regulate populations. Two imported parasites have been released in Florida and these show some promise. The sphecial wasp Larra bicolor (americana) restricted to southern Florida seeks out the mole cricket in the tunnel, paralyzes it and lays an egg on the thorax. In about 2 weeks the developing wasp larvae kills its host. The other imported parasite is a Tachinid fly called Ormia depleta. This fly is attracted to the sound produced by the mole crickets. After finding the mole cricket, the fly lays an egg on the host. The developing maggot stage then kills the host.

 

Cultural Control

The combination of fertilizing, irrigating and rolling the turf in the spring will lessen the spring tunneling damage. The rolling helps prevent the root system from drying out in light sandy soils.

 

Chemical control

Because mole cricket flights occur twice a year and both adults and nymph tunnel extensively, the risk of continuous reinfestations is high. Therefore two insecticide treatments may be required. Contact insecticides such as Mocap, Triumph or Oftanol are most effective against the newly hatched crickets. With late season outbreaks or with early spring tunneling short residual insecticides such as diazinon, Orthene 75 S or Turcam are recommended. Insecticide baits also work well against the nymphs but are relatively ineffective against adults in Fall. Regardless of the insecticide strategy selected, the adults are very difficult to control.

by Dr. Lee Hellman, Department of Entomology and Dr. J. Kevin Mathias, Institute of Applied Agriculture