Flea Control with Parasitic Nematodes Not a Sure Thing
By: Robert A. Dunn, Department of Entomology and Nematology, University
of Florida - IFAS
Fleas are bugging a lot of people and pets! The common "cat flea" (the same flea attacks cats, dogs, and our ankles) seems to be everywhere this year. Recently, consumers, pest control firms, and veterinarians all have raised questions about new flea-control products that are based on an insect-parasitic nematode. Some registrants' claims include "One application lasts up to four weeks;" "95% mortality of the immature flea within 24 hours;" "Will not harm humans, pets, or beneficial insects." How well do these claims hold up? Can these good-guy nematodes provide pets and their owners the promised relief from the pesky populations of flea larvae that infest soil and turf around homes?
First, safety: The insect-parasitic nematodes being marketed for flea control are, indeed, safe. They are not the nematodes that attack people, pets, or plants. They are limited to certain kinds of insects, and have also been found to be effective biological control agents against several other kinds of insect pests that live in the soil.
As to their effectiveness, there is no clear-cut answer. There certainly is not enough research under Florida field conditions to justify an unlimited recommendation for their use. Results of trials done under artificial conditions in North Carolina, California, Texas, and Louisiana have been very promising. They sometimes have provided more than 95% control of flea larvae in carefully prepared soil mixes. However, they were much less effective in several preliminary trials conducted in Florida.
In Gainesville, Florida, applying this same nematode to turf plots similar to many lawns did not reduce the numbers of adult fleas that emerged during the following 10 days. In laboratory experiments designed to determine what might have caused the nematode treatment to fail, the effectiveness of the nematodes was strongly influenced by the relative amounts of sand and clay in the soil, and how wet it was. Nematodes were most effective against fleas in moist sandy soils. Those are conditions in which fleas survived most poorly whether treated with nematodes or not, and also the most favorable conditions for nematode survival and activity. Flea control with the nematodes was least on natural turf and best on bare soil surfaces which had adequate moisture.
Further research is clearly needed to reconcile the differences in results from Florida and some other areas. For now, these nematode-based products may give consumers a chance of acceptable control of fleas in the landscape when they are applied exactly as directed by the manufacturer. The nematodes may fail in some environmental conditions common in Florida (especially dry locations such as lounging areas under shelter of buildings). They may not reduce flea populations as completely as some chemical treatments. However, many consumers will consider it real progress to be able to reduce flea populations in their exterior premises with an environmentally benign product. Of course, to achieve the best flea control, infested indoor areas and pets must also be regularly treated as recommended by animal health care professionals.