By Alice Marty, Mobile County Master Gardener www.mobilecountymastergardeners.org
While gazing out the window at a part of our lawn that had been slowly turning into brown spots and weeds, I noticed something new. Small hills of chewed-up soil. Lots of them. It was as if the night crawlers had a convention and didn’t clean up after themselves. Of course, being a curious Master Gardener, I ran to the computer to research what may have caused yet another lawn problem. After surfing through the Extension sites from three southern states, I had my answer: mole crickets! My only other experience with them was seeing dead ones on a golf course. Now to find an answer to my new dilemma.
Mole crickets are in the cricket family. They have paddle-like front feet that propel them along just under the surface of the ground. As they go, they chew off grass roots and shoots which comprise most of their daily diet. This leaves brown dead spots in the lawn which weeds quickly fill in. Predators such as raccoons, armadillos, and birds recognize the sites as possible food and enlarge them, looking for a mole cricket meal.
Mole crickets do the most damage in spring (March through June) or fall (late August through October). Only one generation is born each year. Eggs are laid in April and May. Besides their tunneling ability, the nocturnal mole cricket can fly great distances. Males call from the entrance of their tunnel and the females fly to find them.
How do you know if you have mole crickets? Simply mix 1.5 ounces of lemon-scented liquid dish detergent with 2 gallons of water. Pour it over a 4ft. square area. Within 3 minutes mole crickets, and many other insects and worms, will emerge to get fresh air. If as many as 2 mole crickets emerge, you have a mole cricket problem.
Pesticide in granular or liquid form has been used to eliminate mole crickets for many years. It is still the fallback treatment at most golf courses. Multiple applications are needed, non-target insects may be affected, and some areas of pasture and residential areas no longer allow pesticide use.
The University of Florida began studying mole cricket control in the 1980s. Since mole crickets are native to South America, it made sense to search for natural enemies in their native environment. Using biological organisms for control has many benefits. Effective organisms react only with the target organism. Once they are established, little maintenance is needed. They are safe for humans, pets, livestock, and groundwater. Balance is the planned outcome, keeping the population below the number to cause host plant damage.
The natural enemy of all mole cricket species is the Larra wasp. She lays two or three eggs per day and up to 100 in her lifetime, each on a mole cricket. The egg hatches and the wasp larva feeds on the mole cricket’s blood. The death rate is 100% for mole crickets affected by the eggs.
About 25% of the mole cricket population is killed by a generation of the Larra wasp. Compared to the one generation of mole crickets a year, the Larra wasp has three generations in a year. The wasp is a day-active insect. It enters the mole cricket tunnel and herds it to the surface, confusing the nocturnal insect. The wasp then stings the mole cricket so a short paralysis will begin. It then lays an egg on the bottom of the cricket. When it hatches, it stays attached to the outside of the cricket, feeding until it forms a pupa.
Larra wasps do not sting humans unless you are holding them in your hand. They are solitary and do not make a nest to defend. They would rather flee than sting.
Attracting and promoting these wasps on your own property is relatively simple. Plant their favored host flowering plants: Spermacoce verticillate, shrubby false buttonweed; Whitehead broom; Southern larraflower, Chamaecrista fasciculata, Partridge pea; and/or Pentas lanceolata, white flowered penta. Of the three, the penta is the easiest to find as plants or grow from seed. Then, sit back and watch nature take its course.
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