Southern - Tawny - Short-winged

Two specie of pest mole crickets are prevalent in south Florida pastures. These are the southern and the tawny. A third one, the short-winged, is restricted to coastal areas. Adult mole crickets are about an inch long, light brown in color, and have front legs that are well adapted for tunneling through the soil. All were introduced around 1900 at the seaports of Brunswick, Georgia in the ballast material of ships from the Atlantic Coast of south America. From the port, the southern and tawny mole crickets spread westward and southwards. They have become serious pests in Florida because they have few natural enemies, Florida's sandy soils favor their development and multiplication, and above all there are millions of acres of their favorite host grasses - bahiagrass and bermudagrass. Mole crickets damage pastures in two major ways: (1) By tunneling through the soil near the surface, they loosen the soil, uproot and dry out grass root systems. (2) They feed on grass roots, causing dieback and eventually bare soil. Tawny mole cricket is the most serious pest on bahiagrass pasture because it eats all parts of the plant (leaves, stems and roots). Southern mole crickets feed mostly on soil insects and other small animals. Most mole cricket feeding takes place in the night after rain showers and during warm weather. During the night they feed on above-ground parts, biting off stems and leaves, which are dragged into the burrows to be eaten. Roots may be eaten at anytime. Both nymphs and adults come to the surface at night to search for food leaving tunnels in their path and they return to their permanent burrows during the day where they may remain for long periods of time during cold or dry weather. When mole crickets come to the soil surface in daytime (say during flooding rains or mating flights) they are subjected to predators including fire ants, ground beetles, raccoons, skunks, armadillos and several birds.

TAWNY
(Scapteriscus. vicinus)


Adult mole crickets are strongly attracted to specific sounds and to lights during their spring dispersal flights. Mole crickets deposit their eggs in chambers dug out within the upper 6 inches of soil. A female will excavate three to five egg chambers and deposit about 35 eggs in each chamber on the average. In south Florida, egg laying usually begins in early March, reaches a peak in May but may continue throughout the year. Approximately 75% of total eggs are laid by the month of June. Eggs deposited between May and June require about 20 days to hatch but longer time is required during cooler periods. Peak egg hatching occurs from June to August in south Florida.

Monitoring:

Mole cricket numbers at any site are estimated by three main methods: 1) Soil flushing, 2) Pitfall trap, and 3) Sound trap. For the flushing method, mix 3 fluid ounces of dishwashing detergent in 5-gallon pail-full of water, and drench 4 square feet with this solution. Observe the area for about 2 minutes and count the crickets as they surface. Linear pitfall traps (see diagram) is ideal for monitoring live young (nymphs and juveniles) mole crickets on a pasture. They are constructed by cutting a slot approximately 1 inch wide length-wise in a section of 3-inch diameter PVC pipe. This pipe is then buried in the ground so the slot is at or slightly below the soil surface, with one end feeding into a 5-gallon bucket and the other end capped. Four 10-ft PVC pipes as described feed into a bucket to form the trap. Sound traps attract adults to the highly amplified synthetic or recorded call of male mole crickets. A Sound Trap consists of a caller situated over a collecting device that catches the crickets as they land. The collecting device may be as simple as a child's wading pool filled with water or a specially constructed aluminum frame (with a 1.5 m diameter) covered by a fishing net which feeds into a collecting bucket (see photo). The record nightly catch for a "standard" sound trap used by the University of Florida is 17,000 tawny mole crickets on March 21, 2000 (see photo). Sound traps are effective only during flight seasons in spring and fall and only adults are taken.







Mole cricket Nematodes

Nematodes that infect and kill insects also known as entomopathogenic nematodes have been known since the 17^th century but it was only in the early 1990's that Dr. Grover Smart Jr. of the University of Florida selected a specific type called the "mole cricket nematode" (Steinernema scapterisci). This nematode was imported into Florida from South America, the original home of pest (scapteriscus) mole crickets. An area in the anterior part of the intestine of the infective juvenile nematodes is modified as a bacterial chamber. In this chamber, the infective juvenile nematode carries cells of a symbiotic bacteria which are usually of the genus Xenorhabdus. The nematodes act as vectors, transporting their bacteria symbionts into the blood stream of an infected mole cricket host, inducing a lethal septicemia usually within 3 days of infection. The bacteria contribute to the symbiotic relationship by providing nutritional requirements for their nematode partners during reproduction in the insect cadavers. The bacteria also maintain suitable conditions for nematode reproduction in dead mole crickets by producing antimicrobial substances that inhibit the growth of a wide range of other micro-organisms. Inside the mole cricket, the juvenile nematode feeds on bacteria and their metabolic products, and molts to males and females which mate and produce two generations of juveniles. The late second-stage juveniles cease feeding, incorporate a pellet of bacteria in their bacterial chamber, and molt into the third stage (infective) juveniles which leave the cadaver in search of new host. The cycle from entry of infective juveniles nematodes into a mole cricket host to emergence of new infective juveniles usually takes 7 to 10 days and as many as 50 thousand infective nematodes may emerge from a dead mole cricket (see photo). Hence, insect control with nematodes may be self-sustaining under appropriate environmental conditions.

In summary, the new mole cricket task force has formed partnerships within the research, technology and clientele community, secured a legislative supplemental budget request for the FDACS, submitted a Florida FIRST Initiative Project proposal (funded) and obtained nematodes for field tests in central Florida. These efforts require continuous communication (as done here), coordination and diligence to sustain momentum on controlling pasture mole crickets.

To responed to the "Article of the Month" -
Controlling Mole crickets on Bahiagrass Pasture
with Nematodes

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