Very brief summary

Dr. Giblin-Davis explained that nematodes are round worms, one of three phyla of worms (the others being the segmented worms and the flat worms).  Nematodes occur in large numbers and are widespread throughout much of the soil and living matter of the earth.  Nematodes parasitizing animals are often painful and can cause horrible disfiguring diseases. There are ancient even biblical references to some of these afflictions.

Plant parasitic nematodes are highly specialized, with dagger like feeding tubes called stylets.  The species of nematodes that attack turfgrasses do not affect animals.  Plant parasitic nematodes vary from ecto-parasites living outside their host to endo-parasites living inside their host, with some nematodes intermediate.  As with all nematodes, plant parasitic nematodes are aquatic animals.  They live in the moisture in the soil.  Some plant parasitic nematodes are large, e.g., the sting nematode is about 2 mm (2000 micrometers) long.

Because of their damage to root systems, nematodes are highly destructive to many crops.  On Florida golf courses highly toxic nematicides are sometimes used to manage nematodes, and the average amount of such products as Nemacur is several times greater than in other parts of the United States. The kinds of pesticides used against nematodes include both the fumigants which kill most organisms, and organophosphates (OPs) and carbamates which are cholinesterase inhibitors.  Human and nematodes both need cholinesterase to regulate the firing of nerve synapses, thus the same products that are harmful to nematodes are harmful to people.

Chemical methods for managing nematodes have been limited by toxicity and the apparent tendency of soil to become "resistant," it is hypothesized, by the selection of microorganisms that can metabolize the nematicides more quickly as a food source.  Non-chemical approaches have not been very successful so far.  There are documented instances of host resistance (though some of the more serious parasites such as the sting nematode have a very large host range).  Organic amendments have been encouraging for nematode control in some cases, but the amounts of such products needed are cost-prohibitive, and it is difficult to separate out the fertilization response.  A bacterium, Pasteuria spp., is a potential biocontrol agent, to be used in inoculative and augmentative approaches.  While the bacterium is specific against certain nematodes, the difficulty now is in rearing it in sufficient quantities for use on turf, because it is an obligate parasite, and it is difficult to rear nematodes in large quantities.

Important plant parasitic nematodes (which also attack turfgrass) and which should be memorized are:

English common name		Latin scientific name
sting nematode		Belonolaimus longicaudatus
lance nematode		Hoplolaimus galeatus
rootknot nematode		Meloidogyne spp.
ring nematode		Criconemoides spp.

An important beneficial nematode used in biological control of mole crickets is:

English common name		Latin scientific name
"mole cricket nematode" (unofficial)		Steinernema spp.

Links to nematode resources