Will Hudson’s Ph.D. thesis was on the subject of tawny mole crickets. That was in 1985, and he’s been studying and trying to control them ever since. These critters, introduced from South America possibly as much as 100 years ago, have become a permanent problem across a wide swath of coastal states from North Carolina to Texas, but they are manageable.
“They’re one of our real pests down here on the coastal plain,” says Hudson, professor of entomology and extension entomologist at the University of Georgia in Tifton. He notes that the tawny mole cricket, Scapteriscus vicinus, is one of several mole crickets in this region, including a native species, but it is by far the most destructive. Fortunately, it does not tolerate drought conditions or heavy soils well and has not spread into other areas. In Georgia, for example, it occurs only in the southern two-thirds of the state. “They were a limiting factor on sod production and on pastures.”
Tawny mole crickets love to eat grass. They can be a problem on plants such as agricultural crops, but the lush turfgrass found on sod farms and golf courses are where they have become a primary pest. The cricket feeds on every part of the grass plant, starting at the top and working its way down. In addition, they churn up the ground by tunneling and surfacing. Besides the feeding destruction, the tunnels can affect the surface of manicured turfgrass.
Adults, as well as immature crickets, will feed on grass. In Georgia, adults emerge from tunnels and begin flying around and laying eggs in the spring, but this can be as early as February in parts of Florida. The resulting nymphs then begin feeding, so from that time until cold weather hits, crickets do nothing but eat and can cause severe damage to turfgrass.
Hudson says there are limited cultural controls for these hardy pests. Keeping turf healthy and grass height as high as possible will reduce the visibility of their damage, but in some areas, such as golf course greens, this isn’t possible. He points out that some types of grass are less preferred as feeding sites. For example, tawny mole crickets favor fine-textured bermudagrass over zoysiagrass and centipedegrass, so some damage could be avoided by planting the last two types. Also, TifSport is touted as a good choice of a hybrid bermudagrass, because resistance to tawny mole cricket feeding was an element of the variety’s selection process.
“There are quite a few chemicals that are labeled for tawny mole cricket control,” Hudson says, but none will permanently get rid of this pest. It lives underground much of the year, and grass provides a nice protective buffer for it. That said, his tests show some good management options. He notes that as crickets get to a level of two or three per square yard, treatment generally becomes necessary.
His preferred chemical is fipronil (Top Choice). A granular application the last week of June or first week of July in most places in the South will suppress the newly emerged nymphs before they can do damage. Hudson says that one application is usually enough to last the season, since in most areas there is only one generation hatching. Since fipronil is also a control for fire ants, in any area where the ants are a problem this is a good choice in that it kills two pests. It is critical to apply the labeled rate.
The neonicotinoids are less expensive, Hudson says, but they are also less effective if not timed exactly right. Imidacloprid (Merit and other brands, including combination products) and clothianidin (Arena and Aloft) are both effective, but must be applied before the cricket eggs begin hatching. They can be granular or liquid applications, but Hudson says that the liquid formulation allows more precise calibration for many turf managers. The neonicotinoids are also good for controlling white grub, so if the other predominant pest in the area is a grub, this class of chemicals is a good choice. Bifinthrin (Talstar and other brands), a pyrethroid, is another insecticide that has proven effective for many years.
Baits are another possibility, but Hudson emphasizes that these will usually only get an infested turfgrass facility by until another insecticide is applied. Thus, they are an interim solution to limit damage early in the year when tawny mole cricket adults emerge from their winter tunnels and begin feeding. They are particularly applicable on high-visibility areas, such as golf course greens, and an added benefit is that golfers will see the dead crickets and be reassured that the superintendent is doing something about this nuisance pest.
“You get a reasonable amount of kill,” Hudson says, noting that baits should be spread late in the day so they will be there when the crickets come out to feed at night. There are many bait brands available, but he has found that the ones that use carbaryl and chlorpyrifos as the active ingredients to be effective in tests. Advion mole cricket bait, with indoxacarb as the active ingredient, is also available for commercial use.
One of the most promising areas in the management of this introduced pest is the use of biocontrols. One that turf managers can purchase and spread themselves is a nematode imported from the cricket’s home regions, the commercial form being Nematac S. It is deadly to tawny mole crickets though slow to act. The product must be distributed in cricket-infested areas and then irrigated to activate it. Dry turf conditions and sunlight are harmful to the nematodes, so follow label instructions when applying.
Hudson points out that distribution of this nematode, Steinernema scapterisci, which was developed and the product patented by the University of Florida, is having a permanent deleterious effect on mole crickets. It was first used in the 1980s, and it becomes established in the environment and one of the natural deterrents for the cricket. Whenever he captures adult crickets for testing he finds up to 50 percent infested with the nematodes.
There are also an introduced wasp and a fly that are natural parasites of the tawny mole cricket. A turf manager can’t buy these, but one or more of the parasites have been introduced to various parts of the cricket’s territory. The wasp Larra bicolor in particular has been seen as successful, but as Hudson points out, all of these biocontrols are well established in some areas and chemical treatment is still sometimes needed. He has hopes, however, that in the future a more natural balance will be established that will mean less frequent chemical applications.
One thing seems certain, however. The tawny mole cricket is here to stay, and turf managers must learn to deal with it.
Don Dale resides in Altadena, Calif., and is a frequent contributor to Turf. He has covered the green industry for more than 10 years.