Mole crickets have traditionally been considered Southern golf course pests, but their impact goes beyond just golf courses and just the South. Athletic fields, commercial properties and home lawns can come under attack by mole crickets. While mole crickets do appear more commonly in sandier soils and in warmer climates, they pop up throughout the eastern two-thirds of the United States.
Mole crickets are subterranean insects, meaning that they spend most of their lives in the soil. This makes them a little more difficult to manage than some other turfgrass insects because their activity is hidden from us and serious damage to the turfgrass is often the first sign of an infestation. Equally important is the fact that the thatch and soil act somewhat as a means of protection for the mole cricket from any control we might apply. For these reasons, it is important to develop a good understanding of mole cricket biology. A poor appreciation of what mole crickets are doing at any particular point in time is a recipe for failure.
The first element to understand is the life cycle of the mole crickets. Mole crickets undergo what it referred to as gradual metamorphosis. In other words, once the mole crickets hatch until the time they become adults, the crickets look much the same. Similar to the manner in which a child looks like an adult, small crickets look much the same as when they get older. When finally mature, mole crickets will possess wings.
The process of going through this development begins in the spring when adult females lay eggs in small groups of 12 to 20 in the soil. The eggs typically hatch in about three weeks and the small nymphs begin feeding and growing. The small nymphs are the easiest to control, yet are the least likely to draw attention to themselves. As a general rule, you cannot observe visible surface damage until the crickets are about 3/4 inch long. Even though their feeding isn't visible, you can monitor these crickets using a technique known as a soapy water flush. You can create the soapy water flush by adding approximately two ounces of liquid dishwashing detergent to one gallon of water. Slowly pour this solution over a 3- × 3-foot area. As the soapy water soaks into the soil, the small crickets will rapidly emerge to escape. Keep watch over the area during the next 3 to 5 minutes and you will be able to determine if crickets are present and their size. As crickets become larger, this technique becomes less effective.
Crickets overwinter either as large nymphs or adults and may continue to feed depending upon winter soil temperatures. The warm spring weather allows all crickets to complete development to adults. When they reach adulthood, mating soon begins. The population of adults mate and lay eggs at that time. Most mating and egg-laying occurs in the spring.
The adult males make a small chamber in the soil from which they emit a mating call to attract females. Males often make their calling chambers in areas of moist soil, as it enhances distribution of the sound. More importantly, the females often lay eggs near the area where they mate. This helps them ensure that they lay eggs in moist soil, increasing the likelihood the eggs will hatch and the newly-hatched crickets will survive. The need for soil moisture most likely influences when the mature mole crickets become pests. Periods of increased rainfall, which coincide with the mating period, may create more sites for mating and egg laying because they provide more areas of moist soil (in addition to the normal moist-soil areas near ponds and streams and in low areas or areas receiving significant irrigation).
TYPES OF MOLE CRICKETS
Two species of mole crickets are responsible for the bulk of turf damage in the southeastern United States. The tawny mole cricket feeds primarily on the roots of turfgrass while the southern mole cricket is more of a predator, tunneling through the soil to find other creatures to eat. Both species can cause serious turf damage. Except in south Florida, the life cycle for both species is quite similar in that they both have one generation per year. This means it takes one year for the cricket to complete its development and reproduce. Shortly after mating in the spring, the adults die.
The short-winged mole cricket doesn't fly, and its distribution is limited to south Florida. The native northern mole cricket is found throughout the eastern two-thirds of the United States. It is most common near water, especially around ponds and lakes, and along creeks, streams and rivers. This is not commonly a turfgrass pest, but on occasion does cause serious problems. The northern mole cricket may require more than a year to complete its life cycle in many locations.
The three most troublesome species, the tawny, southern and short-winged mole crickets, are all introduced species. This simply means they are not native to the United States, and were introduced by accident about 100 years ago. As a result, these crickets are not kept in check by a large number of natural enemies. Their pest status is due, in part, to the absence of predators and parasites to attack them.
CONTROLLING MOLE CRICKETS
How do you go about effectively managing mole crickets in turfgrass? Selecting the appropriate insecticide is only a small part of the overall program. Incorrect use of even the best product can lead to disappointing results. Putting your knowledge to use about pest biology and occurrence in your area is critical to success.
First, you need to know the species of mole crickets you are dealing with. Then you must recognize the life cycle and timing of occurrence of this species in your area.
Typically, mole crickets lay their eggs in spring, but hatch can vary by well over a month in the southeastern United States alone. If you know when egg hatch should occur, then you know when you should begin the soapy water flushes to confirm the presence of small nymphs.
If you keep good records of where mole crickets occur (wher you have observed serious damage in the past), then you can efficiently use your time by implementing the soapy water flush in those areas that have a history of mole cricket problems.
Mole crickets are creatures of habit and often occur in the same areas over and over again. This isn't to say they can't show up in new areas, but they do have preferred sites.
A conventional insecticide is going to be most effective and control crickets quickly when you target it at the small nymphs. These nymphs are more susceptible and are feeding near the soil surface. As crickets get larger, they not only are a little hardier and tougher to kill, but they can also tunnel deeper in the soil and sometimes escape the effects of the insecticide application.
When soil moisture is low, the crickets have a tendency to remain deeper in the soil. Dry soil conditions make mole cricket control more difficult as the cricket's depth decreases the likelihood the insecticide will make contact. Additionally, the dry soil and organic matter may lead to an increase in binding of the insecticide, which results in less availability of the product.
Pre-irrigation of the affected area, as well as post-treatment irrigation, may be beneficial in enhancing mole cricket control. The pre-irrigation helps thoroughly wet the soil and organic matter, which may improve insecticide movement. It may also help move the mole cricket closer to the surface. But don't put too much water out after treatment (more than ½ inch). This may lead to runoff, and our research shows this may actually reduce the effectiveness of the treatment.
In the weeks that follow treatment, monitor control in the most problematic areas with the soapy water flush. Remember that it may take many treatments a week or two to become fully effective. The larger the mole cricket, the longer time required to observe good control.
Research indicates that there is significant variability in control with specific products based upon local conditions. Find out which products are recommended for mole cricket control in your area and which ones perform best.
STEP IT UP
There are four important steps to mole cricket control.
Map the areas of infestation. You can often do this in the spring, based upon activity of the adults. The adults usually lay eggs back in the same area where you observed their activity in the spring.
Monitor egg hatch with a soapy water flush.
A couple of weeks after significant egg hatch occurs, apply the appropriate product to control the small nymphs. Applying the product too early may result in the residual activity declining prior to end of egg hatch. Applying the product too late may result in poor control because the earliest hatching crickets have gotten too large.
Perform follow-up monitoring of control and spot treat any areas where you determine the individual control to be less than acceptable.
By following these guidelines and correct timing of your application, you can make great strides in managing this troublesome pest. Like any soil pest, mole crickets are difficult to control and you should never expect 100-percent control.
Dr. R.L. Brandenburg is a professor and extension turfgrass entomologist at North Carolina State University (Raleigh, N.C.).
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