Permanent Mole Cricket Control

After six years of field testing, the entomopathogenic nematode Steinernema scapterisci (Ss) is now commercially available under the trade name Nematac S®. It is produced and marketed by MicroBio, Inc. of Ames Iowa. This product has been found to provide permanent biocontrol of mole crickets with proper timing of application.

Nematac S contains infective juveniles (IJs) which are the only free-living stage of Steinernema scapterisci (Ss) nematodes. The juveniles in Nematac S do not feed but may live for months on stored reserves if kept cool (400F). Once applied on a pasture, their sole function is to search for an adult or pre-adult mole cricket, invade it, and initiate infection. The reproductive stage of the nematodes normally takes place inside a dead mole cricket.

The nematodes do not move far in the soil but depend on mole crickets to move to them. They attach to a mole cricket, enter it through its mouth or spiracles, and initiate an infection. Active dispersal in the soil may be measured in inches. By comparison, dispersal of the nematodes by mole crickets may be measured in miles. Additionally, the length of time that the juveniles survive in soil after application and without finding a mole cricket is days or weeks, depending on soil temperature, type, and moisture, and natural enemies. Survival is better in sandy or sandy-loam soils, adequate moisture, and temperatures between 60 and 700F than in clay soils, excessive moisture, and higher or lower temperatures. There are numerous organisms in the soil that prey on the juvenile nematodes (i.e. mites, fungi and other nematodes). Therefore, large numbers of nematodes are normally applied (~ 1 billion/A), and they must find and infect a mole cricket in the shortest possible time after application for biocontrol to occur.

The seasonal pattern of mole cricket activity in pasture is critical for timing the application of nematodes. Nematodes are more effective on large juveniles and adults mole crickets which have larger body openings that on smaller nymphs. The two recommended times that are ideal for nematode application to pastures in Florida are September to November, and March to May when a high percentage of adult mole crickets are present. Nematode application during these periods should be timed for early mornings or evenings and following rainfall or irrigation to ensure cool, moist conditions necessary for nematode survival. Upon successful entry and infection in mole crickets, the nematodes will reproduce in the mole cricket and recycle back into the soil to allow for long-term mole cricket control.

If you are considering Biocontrol of Mole Crickets on Pastures, the following recommendations amy improve success:

Purchase fresh nematodes (Nematac S) within a few weeks before planned application. (even better to have them arrive as close to application time as possible).

Store nematodes in a refrigerator at about 400F (4-60C).

Transport nematodes to the field in a cooler with ice or in an air-conditioned vehicle. Use a towel or other barrier to prevent direct contact with the ice.

Time application for early mornings or evenings in March-May or September-November.

Apply nematodes to moist soil.

Use a machine with injector tines or a modified slit-seeder that can place the nematodes in suspension 1 inch below the soil surface and close the slit with press wheels. If soil is very moist and plant cover is not too dense, a sprayer rig with filters removed can also be used (check pump and nozzle).

Mix nematodes directly into a tank partly filled with fresh, clean water with the agitator running, and then bring volume up to 100 gallons. Calibrate to apply enough suspension to obtain 1 billion nematodes in 100 gallons of water to an acre.

Apply the nematode suspension in strips, immediately after mixing, while maintaining constant agitation, to one-quarter or one-eighth of the pasture to be treated.

Call the County Extension Office at 259-3520 for more information on Biocontrol Options for Mole Crickets.

Source: Agronomy Notes, March 2002.