Identification
Plant-parasitic nematodes are tiny roundworms, 1/50 to 1/16 inch
(0.4 - 1.5 mm) long. They feed on plants by inserting a mouth stylet
into cells to withdraw nutrients. Soil-dwelling, beneficial
nematodes do not have a stylet and cannot feed on plants. Ectoparasitic
nematodes occur predominately in soil and feed on the surface of
roots while endoparasitic nematodes live and feed mainly inside
of plant tissues. Several species of nematodes may be associated
with turfgrasses in California. Statewide, root-knot nematodes
(Meloidogyne spp.) are the most important nematode pests
Hosts
All turfgrass species
Symptoms
Aboveground symptoms are nonspecific and typically occur as patches
of yellow or wilted plants or reduced growth. Drought stress and
poor nutrition may accelerate the decline. Belowground symptoms vary
with nematode species but in general result in reducing the ability
of roots to sustain foliar growth with water and nutrients. Feeding
by root knot nematodes results in swellings, called galls, on roots.
Severely galled roots may appear malformed and the root system shortened
and thickened. Nematode feeding often predisposes the injured roots
to fungal and bacterial attack.
Favoring conditions
Plant-parasitic nematodes have become an increasing problem in sodded
lawns, especially in irrigated, warm, sandy soils. Runoff water from
infested areas such as a neighbor's yard or sharing of contaminated
equipment can cause the infestation to spread. Heavy traffic, extremely
short mowing heights, and nutrition and water deficiencies also contribute
to the problem. Increasing soil temperatures (70° to 86°F
) stimulate nematode activity.
Monitoring information
A laboratory analysis is required to identify the nematodes associated
with a problem. In order to establish a potential correlation between
nematode presence and observed symptoms, soil and root samples should
be collected from both affected and unaffected areas.
Prevention and management
It is virtually impossible to get rid of nematodes once the turfgrass
is infested. The key to managing plant-parasitic nematodes is to
avoid infestation. Consider seeding rather than sodding, as it is
less likely to introduce nematodes to the soil. Reduce stress by aerating and
by following proper mowing, fertilization,
and irrigation practices for
your turfgrass species. There are no nematode resistant turfgrass
cultivars. Pesticides for nematode management are not available for
home lawns. |
