Native Mole Cricket
- Scientific Name: Gryllotalpa hexadactyla Perty, is the species found in the eastern half of North America, but another species, G. cultriger Uhler can be found in western states. [Phylum Arthropoda: Class Insecta: Order Orthoptera: Family Gryllotalpidae]
- Common Names: G. hexadactyla - northern or native mole cricket; G. cultriger - prarie mole cricket
- Climatic Zone: subtropical to temperate
- Geographic Distribution: These species are native to North America. The northern mole cricket is usually found near wetland sites (along streams and rivers or near marshes) and is commonly found from Canada to southern Texas east of the arid shortgrass prairie zone along the Rock Mountains.
- Damaging Stage: nymphs and adults
- Hosts: Native mole crickets have habits similar to the southern mole cricket in that they seem to prey on other insects. They may feed occasionally on plant material, but his is a minor part of the diet. They may tunnel across any turf in southern, transition or cool-season zones. This tunneling is especially noticeable in the short cut grass found on golf courses.
- Damage Symptoms: Produces typical mole cricket damage due to tunneling. Nymphs and adults tunnel and throw up mounds of soil. Uprooted turf may wilt and die from desiccation. They have become especially noticeable in transition and cool-season turf golf courses where tees or greens have been constructed near wetland sites, especially river flood plains.
- Description of Stages: Mole crickets have incomplete life cycles with egg, nymphal and adult stages. They generally have one generation per year but northern mole crickets may take two years to complete their development in northern states.
Eggs: Rounded elongate, translucent white eggs are placed in clusters usually in very moist soil.
Nymphs: The nymphs look like small adults but do not have functional wings. The wings develop as pads which enlarge with each molt. This species can be identified by the distinctive presence of four tibial dactyls. The nymphs are usually much darker brownish-chestnut color than the non-native mole crickets.
Adults: Adults are generally smaller and thinner than tawny mole crickets. They are about 1 1/8 inch (32 mm) long by 3/8 inch (9 mm) wide, nearly the same as the southern mole cricket. They are a dark brown-chestnut (slight red cast) color and the pronotum is unpatterned. The adults can be distinguished from other mole crickets by the presence of four tibial dactyls. The forewings are very short, only about one-half the length of the abdomen while the hind wings extend past the tip of the abdomen. Males also have a darker rasp and file mark on the forewing base
- Life Cycle and Habits: Native mole crickets have a cycle much like the southern mole cricket. In early spring, overwintered nymphs develop rapidly and reach the adult stage by April and May. The males construct a calling chamber near the soil surface when temperatures reach 60 °F. From these burrows, a series of low pitched trills are made to attract females. After a warm spring rain, especially in Gulf States, numerous females and males take flight. Both sexes can be attracted to lights and areas where males have established calling chambers. In transition and cool-season zones, these flights are rare and the adults seem to merely tunnel or crawl to find each other.
Mated females prefer habitats with a high water table for establishing permanent burrows and to begin egg laying. Favored sites are river flood plains, stream, pond and lake banks, as well as marsh lands. Nymphs disperse by tunneling through the soil in search of insects and other invertebrates as food. This species is cannibalistic and will feed on other species of mole crickets. Most nymphs mature by mid-Fall, but in northern states most do not reach adulthood until the following spring. In Michigan and southern Canada, native mole crickets may take two years to complete development. During periods of drought, this species digs deeper in the soil to reach the water table. During winter months, they dig below the freeze line to survive.
- Control Approaches: The most difficult time to control mole crickets is late fall and early spring when the adults are flying to relocate and mate. These adults may move deep in the soil profile - below the zone where most controls can reach them - during cool or dry soil conditions and are less prone to feed which minimizes their exposure to control materials. There is little that the turf manager can do to prevent this movement and damage.
Cultural Control - Habitat Modification - Mole crickets generally prefer moist soil conditions and populations are generally concentrated near wetlands or waterways. Allowing turf to dry, especially in the spring egg laying period can help discourage females from laying eggs in such areas.
Biological Controls - Encouragement of Natural Agents - Mole crickets are cannibalistic and many young nymphs perish in this manner. Predacious insects, birds and mammals prey on mole crickets but may dig up turf in the effort. The native mole cricket in more nothern parts of its range are more of a curiosity than actual pest.
Chemical Control - Insecticides -
Except in the Gulf States, native mole crickets rarely build up damaging populations. Only in these areas are insecticidal controls recommeded. In more northern states, tolerence should be practiced or a soap solution drench will eliminate the occasional cricket that finds its way onto a golf green or tee surface. In Gulf States, follow the following procedures:
Targeted Treatments. A targeted strategy to control mole crickets with surface insecticide uses a preventive approach “mind set” though the process is technically a curative approach. In this strategy, insecticides that have short residual efficacy against mole cricket nymphs are applied to areas that were mapped and determined to have considerable adult activity in April and early May. The insecticide is applied at egg hatch and every three weeks thereafter until egg hatching stops (usually after two to three applications).
Curative Treatments. The Curative Approach involves broadcast applications of sprays or granules and baiting. Broadcast Application of contact/stomach pesticides are made when the mole cricket eggs are hatching and again when nymphs are about half grown (no more than one inch long). To achieve maximum effect, the turf to be treated should be irrigated for several days before application to ensure that the soil is moist and mole cricket nymphs are near the surface. When rainfall has been sufficient to move nymphs near the surface, pre-irrigation is not needed. To determine whether nymphs are near the surface, apply a light sprinkling (water can) of soapy water. If present, the small nymphs will “pop” out immediately. If it takes several minutes for them to surface, irrigate before making the pesticide application. After application, irrigate lightly to move the pesticide to the nymphs. Inspect treated areas at dawn the following morning to determine treatment effectiveness. Affected nymphs will surface after being exposed to the pesticide. If few or no nymphs are found on the surface, recheck treated areas with a soap flush. If numerous nymphs surface after the recheck, retreat with a different insecticide. Bait-formulated insecticides are usually more effective once the nymphs are longer than one inch. Areas remaining moderate to highly infested after application to control earlier small-nymphs are candidates for treatment with bait. Again, irrigate application to move the nymphs to the surface, but DO NOT IRRIGATE after applying the bait. Baits are most attractive when they are fresh and not subjected to rainfall or irrigation. Also avoid applying the bait if rainfall is expected the night after application. Stopping turf damage from fall or spring migrating adults is difficult to achieve. The turf manager can do little to PREVENT migration or damage. Baits are also suggested when control of adults is deemed necessary.
Preventive Treatments. Insecticides with moderately long residual activity against mole cricket nymphs can be applied to high risk areas at the beginning of mole cricket egg hatch (usually late May to early June). Mapping of mole cricket activity or knowledge of chronic mole cricket damage areas are prime candidate areas for preventive treatments. Both surface and subsurface applications of certain long residual insecticides have been effective for preventive control.
At sporadic times, usually associated with warm and rainy weather, adults move to the surface, tunnel extensively, fly in mass and mate. Research has shown that moist but not saturated sites with dense turf or weed growth is highly attractive to spring-active adults. These sites are where eggs will be concentrated. Mole cricket Activity Mapping has been adopted by many golf course superintendents to identify areas at highest risk of having damaging mole cricket nymph populations.
Mole Cricket Activity Mapping. In the spring, areas where mole crickets are most actively tunneling, emerging and digging back into the soil are where most of the eggs will be laid. A visual inspection of each fairway, wetland margin, and even managed roughs should allow for easy detection of mole cricket "hot spots." It will take time for the turf manager to differentiate between light, moderate and extensive mole cricket activity.
Detecting Mole Cricket Nymphs and Evaluating Control Efficacy. If in doubt as to whether mole cricket nymphs are active in an area, especially when they are small, use of a soap solution drench can rapidly cause the nymphs and even adults to surface. Use one tablespoonful of a household dishwashing detergent per gallon of water (Joy™ and Ivory Clear™ have shown no evidence of phytotoxicity) and apply 2 to 4 gallons of this solution through a sprinkling can over a one square yard of turf suspected of being infested. During dryer conditions, two soakings may be needed to bring mole crickets to the surface. This drench applied after a control application can help evaluate the efficacy of the application.