Article of the Month - July 2007 - Mole Cricket Management

South Florida Beef - Forage Program

"Article of the Month"
July 2007

Mole Cricket Management

by, Steffany Dragon, Hillsborough County Small Farms & Livestock Agent

What are Mole Crickets?
Odd looking crickets, two of which (the Tawny Mole Cricket, Scapteriscus vicinus; and the Southern mole Cricket, S. borellii) are especially destructive to Florida pastures. These brown-ish crickets are covered with very fine hair and have flattened, shovel-like, strong front legs adapted to digging tunnels. They usually grow to 1 ˝" in length.

What do they do?
They spend most of their lives underground making burrows resembling miniature mole tunnels in the soil while feeding on soil insects or plant material. Florida's sandy soils favor the development and propogation of the mole crickets, and and our number 1 pasture grass, bahiagrass, is its favorite host grass. As the mole cricket tunnels through the soil, it basically causes damage by uprooting grass plants, causing them to dry out and die. Damage ranges from thinning of grass stands in small, isolated patches, to killing the grass in an entire area, leaving bare soil susceptible to weed encroachment and causing problems in livestock production such as reduced livestock grazing and therefore lower weights of gain, and the potential for colic in horses due to intestinal sand impaction. Adult female mole crickets place 30 or more eggs in underground cells in the springtime. Eggs hatch in 1 or 2 weeks during warm weather, and are considered nymphs. The crickets become adults by fall and the generation is complete until the following year. There is no doubt that these pests are a great nemesis to producer managing bahiagrass pastures.

Do I have them in my pasture?
In order to control these pests, you must know whether or not they are present. Check areas for signs of tunneling. It is most visible in low-cut grass or closely grazed areas in early morning when the dew is on the grass and the soil may be moist. A method of sampling and 'mapping' where mole crickets are located is called the "Soap Flush." Mix 2 tablespoons of lemon liquid dishwashing soap in 2 gal of water in a sprinkling can, and pour the solution onto 3-4 sq. ft. of pasture. If 2-4 mole crickets emerge within 3 minutes after applying the soap solution, insecticide use may be justified. Flushing is most effective in moist soil and can also be done with a synergized pyrethrin insecticide solution. Remember that mole crickets tend to be distributed unevenly, so samples may have to be taken at various places per given acre and samples averaged for an accurate estimated county per acre. Another sampling method is to use commercially available electronic sound traps that mimic male mating songs. This is used to draw adult females out at night. All adult mole crickets are strongly attracted to lights during their spring dispersal flights in the spring as well.

How do I control them?
Whether you have determined that you already have mole crickets and must get rid of them or that you want to prevent them, there are a few management decisions you can make. In bahiagrass, damage can be reduced by leaving a stubble of 4 inches. This remaining leaf will allow for the plants to remain healthy and have a better chance at resisting mole cricket damage. Overgrazing by livestock (cattle, horses, goats, sheep, etc.) should be avoided at all costs to decrease the risk of severe of permanent damage. In bahiagrass, soil acidity and too much N fertilization can weaken the root system. While the target pH for bahiagrass is about 5.5, a near neutral pH (closer to 7) is recommended for reducing severe mole cricket damage. If you are trying to prevent mole cricket damage in bahiagrass, simply maintain your soil pH at around 5.5.

Using the previously mentioned 'cultural' methods in combination with other pest control methods that minimize risks to human health, beneficial and nontarget organisms, and the environment is recommended and referred to as Integrated Pest Management (IPM). This approach provides longer term prevention and control and may also include the following other methods:

Biological:
Control of mole crickets with natural enemies can be enhanced by applying the nematode, Steinernema scapterisci, which has been proven effective against tawny and southern mole crickets. Once applied, the nematodes locate the mole crickets and release a lethal bacterium to kill their host within 2 weeks. Once dead, the nematodes reproduce inside the dead insect, providing a new generation to seek out and kill more mole crickets. Nematodes are more effective when applied to adults and large nymphs in the spring or fall. The nematode is Nematac SŽ, provided by Becker Underwood and can be purchased from commercial suppliers. Remember that unlike a pesticide, nematodes are delicate living organisms and they must be properly handled, stored, and field applied according to the label (no exposure to direct sunlight or prolonged heat). Here is a list of distributors in the state of Florida where people can purchase Nematac S for mole cricket control.

Helena Chemical, Tampa, FL - Ph# 813-626-5121

ProSource One, Plant City, FL - Ph# (813) 752-1177

Triangle Chemical Company - Ph# (352) 429-0255

LESCO - Ph# (800) 321-5325

Harrell's Fertilizer, Lakeland, FL - Ph# (800) 282-8007

Howard Fertilizer, Orlando, FL - Ph# (305) 258-4700

Southern Agricultural Insecticide, Palmetto, FL - Ph# (941) 722-3285

They do have product available to ship at anytime the customer requests. All shipments will be sent Monday through Thursday via Next Day Air in a temperature controlled package. The product needs to be ordered through one of these distributors. There is a minimum order of 4 trays (a tray is 500 million nematodes) which will treat approximately 2 acres.

Another predator of the mole crickets is the Larra wasp (Larra bicolor) that finds the mole cricket, chases it out of its underground burrow making it emerge from the ground, sting it on its underside and immobilizes it for a few minutes. As the mole cricket lies 'paralyzed' on its back, the wasp lays a single egg on its underside. Once the egg is layed, the wasp leaves and the mole cricket recovers and returns to its below-ground burrowing. The wasp larvae develops as a parasite on the cricket until it kills it. The nymph must be at least 1/3 of its adult nymph size for the wasp to target it. The wildflower, Souther Larraflower (Spermacoce verticillata) provide nectar (food) for the Larra wasp. This wasp does not build nests, is not aggressive, and does not have a painful sting. By having this wildflower in your field, the Larra wasps have a food source and are more likely to establish and persist from year to year.

Chemical:
Liquid and granular formulations of insecticides are commonly applied to the soil to suppress newly hatched mole cricket nymphs from April to June. It is important to read the label because some pesticides should be 'watered in' or applied before a rain to drive mole crickets closer to the soil surface, and move the pesticide into the root zone of the plants where the mole crickets are feeding. This time of the year, bait formulations can be useful. Most of the baits contain wheat bran, cottonseed meal, or another grain product with a 2-5% toxicant. Since mole crickets feed at night, they should be applied early evening from July-September (late summer for larger nymphs). The difficulty here is finding a few dry evenings during our FL summers because bait and water don't mix!

For additional information on mole crickets, please refer to the following references or call your local Extension Agent.

References:

Adjei, M.B., Crow, W.T., Smart,Jr.,G.C., Frank, J.H., and Leppla, N.C. (2006). Biological control of pasture mole crickets with nematodes. EDIS publication ENY-009. Available at: http://edis.ifas.ufl.edu/in123

Buss, E.A., Capinera, J.L., and Leppla, N.C. (2006). Pest mole cricket management. Edis publication ENY-324. Available at: http://edis.ifas.ufl.edu/pdffiles/LH/LH03900.pdf

Frank, J.H. and Sourakov, A. (2006). Larra wasps, larra analis fabricius; mole cricket hunters, larra bi color fabricius (suggested common names) (insecta: hymenoptera: sphecidae). Edis publication EENY-268. Available at http://edis.ifas.ufl.edu/in451

To responed to the Article of the Month -
"Mole Cricket Management"

Go to Cattletalk-l.

"Article of the Month" Archives

Back to the South Florida Beef-Forage Program HomePage