Biology and Control of Mole Crickets 3 the Area After Flushing Can Minimize Sun Scalding of the Turf
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ALABAMA A&M AND AUBURN UNIVERSITIES Biology and Control ANR-0176 of Mole Crickets Mole crickets have become the most destructive insect pest on turf and lawns in Gulf Coast states. Estimates of damage and replacement costs for turf and pastures in these states are in the millions of dollars annually. This review of the biology, ecology, and management of mole crickets is intended as a reference for homeowners, turf professionals, and local Extension agents. Pest Mole Crickets Brief History and Their Cousins of Mole Crickets The insect order Orthoptera in the United States includes crickets, grasshoppers, Scapteriscus mole crickets were and mole crickets. Within this not known to occur in North order, grasshoppers are a separate America before the early 1900s. subgroup from the field crickets Three species in the genus and mole crickets. Crickets (such Neoscapteriscus were introduced as the field cricket Gryllus spp.) near the Georgia and Florida are related to mole crickets but do border from South America. not live in soil. The short-winged mole cricket (N. Two families of crickets have abbreviatus) is the least known the common name of mole of these species. It is incapable of crickets. Pest mole crickets have Figure 1. The hearing organ on the mole flight due to its shortened wings, cricket is analogous to human ears. digging front legs and live most and it basically has established of their lives in soil, similar to only in Florida. Two additional the mammalian mole. Pygmy species, the tawny mole cricket forelegs that separate them from mole crickets, much smaller and (Neoscapteriscus vicinus) and the native species, which have four unrelated to pest mole crickets, the southern mole cricket claws. They have long antenna and are not associated with damage to (Neoscapteriscus borellii, formerly strong, digging forelegs. Nymphs turf or pasture grasses. N. acletus) spread and continue resemble adults but are smaller in What people commonly to spread across the Gulf Coast size and lack fully grown wings. states and north along the know as mole crickets (family At maturation, the front wings of Gryllotalpidae) in North America Carolina coast. Neoscapteriscus also are reported from isolated southern mole and tawny mole are represented by ten species crickets are folded back and almost in three genera: Neocurtilla, locations in western states. In the southeastern United States, mole reach the tip of the abdomen. Gryllotalpa, and Neoscapteriscus Coloration of the pronotum and (formerly listed as Scapteriscus). crickets are most likely tawny and southern mole crickets. the dactyls on the forelegs can be Of these, Neoscapteriscus spp. used to differentiate between the is the common pest species in other Neoscapteriscus species. the southeastern United States. Description Gryllotalpa major andARCHIVE Neocurtilla of Neocapteriscus Tawny mole crickets are typically hexadactyla are native and, on Mole Crickets golden brown with a mottled rare occasions, associated with coloration on the pronotum damage to grass. Interestingly, in Adult mole crickets are large (fig. 2). Southern mole crickets are the early 2000s a campaign (1 to 1¼”) with elongated bodies. grayish with four pale dots on the began in England to protect The front pair of legs bear pronotum (fig. 3). European native mole crickets dactyls and the hearing organ called the tympanum, which is Southern mole crickets are the (Gryllotalpa gryllotalpa) from only species that have four pale extinction. Loss of grassland analogous to human ears (fig. 1). Neoscapteriscus mole crickets dots, although individual southern habitat is partially blamed for mole crickets may lack these dots. losses of this native species. have two clawed dactyls on their www.aces.edu Since pronotum color can vary, the appearance of the tibial dactyls is Table 1. Average instar collected at each location a more reliable characteristic to Location June 15 August 17 separate these two species. The tawny mole cricket has a V-shaped space between the dactyls; that is, #6 2nd 4th the dactyls are close together at the base, generally narrower than the #11 2nd 4th range (2–7) width of one dactyl. The southern mole cricket has a U-shaped space (fig. 1); that is, the base of #18 N/A 9th the dactyls is more widely spread (about the width of one dactyl). Note: Longer flight periods and variations in egg incubation times may produce significant variations in population age on a given site. Life Cycle and Damage and dispersal flights take place Egg incubation periods range All Neoscapteriscus mole crickets February to March for tawny and from 11 to 32 days for tawny mole produce one generation per year. southern mole crickets. Flight crickets and from 16 to 37 days The exception is in South Florida, occurs within 1 to 2 hours following for southern mole crickets. Egg where two or more generations may sunset. Males sing (call) to females incubation is shorter at warmer soil occur, especially for short-winged from a special chamber in the temperatures (≥84 degrees F) and and southern mole crickets. ground. Females respond to the longest when soils are cooler (≤63 Mole crickets spend their lives in calls that are unique to the males of degrees F). Longer flight periods soil, with occasional mating and their species. (This is the basis for an and variations in egg incubation dispersal flights as adults. Mating acoustic trap used mainly for mass times may produce significant collection of adults for research.) variations in population age on a given site (table 1). Flowering of the Fall flights for dispersal are also herbaceous perennial Agapanthus common. Flights and egg laying (fig. 5) is generally a good indicator may continue for sixty or more of peak egg hatch. days, with peak egg laying for tawny and southern mole crickets Mole crickets develop from eggs to occurring when soil temperatures adults through a series of seven to are around 75 degrees F. Tawny ten nymph stages, with no pupal mole crickets will complete most stage (fig. 6). After hatching, young flight activity before egg laying, nymphs tunnel extensively as but southern mole crickets may fly they feed and develop rapidly. between egg-laying events. Nymphs (fig. 7) resemble adults Soil moisture is a good predictor of egg-laying success and may trigger egg-laying behaviors. Eggs are laid in clutches of ten to sixty eggs Figure 2. Tawny mole crickets are (average is thirty-five) in a chamber typically golden brown with a mottled 1 to 12 inches below the surface, coloration on the pronotum. depending on soil moisture (fig. 4). ARCHIVE Figure 4. Eggs are laid in clutches of ten to sixty eggs in a chamber 1 to 12 Figure 3. The southern mole crickets Figure 5. Flowering of the herbaceous inches below the surface, depending on perennial Agapanthus is an indicator are grayish with four pale dots on the soil moisture. pronotum. of peak egg hatch. 2 Alabama Cooperative Extension System only in sand-based greens and tees May–June-------------------------------------------Fall----------------Spring or sand bunkers. Year 1-----------------------------------------Overwinter------Year 2 Belowground tunnels erupt to the surface causing numerous small Immature---------------------------------------------------------Reproductive mounds of soil (fig. 12). Tunneling increases as the season progresses. When combined with feeding, extensive tunneling can result in desiccation and susceptibility to other types of damage from foot traffic, golf carts, drought, or possibly pathogens such as Rhizoctonia root rot. Mole crickets feed on grass roots but also feed at night at the surface on grass blades or other insects. Surface-feeding Figure 6. Mole cricket development begins at egg hatch in early summer behaviors are the basis for the use and is not completed until the insects mature in the spring of the following of baits discussed later. year. (Image credit: D. Shetlar, The Ohio State University) Mole crickets spend most of the but lack wings, except for small mole crickets reflects their more year as developing nymphs in the soil. Since egg hatching occurs wing pads; wings develop about carnivorous feeding habit. Both midyear, mole cricket development two molts before the adult form. species, however, are omnivores spans 2 calendar years (fig. 6). As they age, nymphs form more and capable of feeding on both By December, mole crickets have permanent tunnels. plants and animals (mainly insects). developed into adults, and the rest Individuals develop faster when are large nymphs that will complete Mole crickets are particularly they eat animal tissue as compared development in spring of the sensitive to desiccation and move to just plants (fig. 10). following year. About 75 percent in the soil profile in response to of southern mole crickets and 15 changes in soil moisture. There is Tunnels are more extensive in percent of tawny mole crickets a significant relationship between soils that are sandy or loamy sand; overwinter as nymphs. soil moisture and damage; even they are less complex in areas with On a particular site, mole cricket short-term changes in soil moisture mostly clay soils (fig. 11). Tunnels populations are often a mixture of due to irrigation can cause damage. make soils more porous, allowing southern and tawny mole crickets, more surface water to enter the soil Underground, the tunnels of usually dominated by one species. profile. In areas with heavy clay Fall tunneling activity (September tawny mole crickets (fig. 8) branch soils, tunneling is generally evident more at the surface with multiple to October) as well as activity in entrance holes. Southern mole cricket tunnels (fig. 9) have one main surface entrance and branch deeper in the soil. More tunneling at the surface likely reflects the more herbivorous nature of tawny mole crickets; whereas, the fewer branching tunnels of southern ARCHIVE Figure 8. The tunnels of tawny mole Figure 9.