Nematodes - Westcott's Plant Disease - page 243

Longidorus elongatus On grape, causing males are slender, wormlike. Females deposit

eggs in a gelatinous mass, and the body is not
turned into a cyst as in Heterodera (see Fig. 3 ).
Root knot is the best known nematode disease,
with over 2000 plant species susceptible to one or
more forms of Meloidogyne. Root knot was first
reported in England, in 1865 on cucumbers; in
1876 it was recorded in the United States on
violet. Infected plants are stunted; they often
wilt, turn yellow, and die. The chief diagnostic
symptom is the presence of small or large swell-
ings or galls in the roots (see Fig. 4 ). They are
nearly round or long and irregular, but they are an
integral part of the root and cannot be broken off.
This differentiates them from beneficial nodules,
formed on legume roots by nitrogen-fixing bac-
teria, which can be readily broken off.
Root-knot nematodes occur in practically
every state. We used to think they were killed
by northern winters, but some species can survive
extreme cold. They do have fewer generations in
the North and do not build up such large
populations as in southern sandy or peat soils.
Grasses and grains are about the only plants
immune or resistant to root knot.
The long, thin young larva takes form inside
the egg, breaks out, and migrates through the soil
to a root. It moves in to the axial cylinder and
there becomes sedentary. It injects a secretion of
its esophageal glands into the tissue by means of
its short buccal stylet, and this stimulates the
formation of 3 to 5 giant cells around the injection
point. The nematode absorbs its food from these
nectarial cells the rest of its life. As it feeds, the
larva swells rapidly into a sausage-shaped body,
which, in the female, becomes whitish and pear-
shaped, large enough to be just visible to the

necrosis and excessive root-branching.
Longidorus maximus Reported associated with
celery, leek, lettuce, and parsley.
Paralongidorus sylphus Thorn's Needle Nem-
atode , fairly common in the Pacific Northwest,
causing severe stunting of peppermint.

Meloidodera

Heteroderidae. A new genus, a link between
Heterodera and Meloidogyne ; eggs are retained
in the female, but there is no distinct cyst stage;
second stage larvae invade roots but no galls are
formed.
Meloidodera floridensis In roots of slash pine

in Florida.

Meloidoderita

Tylenchulidae sp. On grapes. Males developed
in soil and have a degenerate esophagus that lacks
a stylet.

Meloidogyne

Heteroderidae. Root-knot nematodes, formerly
considered one species, now known to be several,
distinguished by slight morphological differ-
ences such as striations, perineal pattern of the
tail, type of galls formed, host preferences, and
somewhat by locality. Females are white, pear-
shaped to sphaeroid with elongated necks, slen-
der stylets with well-developed basal knobs;

Fig. 3 Root-Knot
Nematode Galls on Potato