Nematodes - Westcott's Plant Disease - page 247

Pratylenchus pratensis DeMan's Meadow
Nematode . Important on grasses, strawberry,
lily, and narcissus; reported on a great many
other hosts, but there may have been some con-
fusion with other species.
Pratylenchus safaenis On soybean, corn, cot-
ton, millet, rice, and sorghum.
Pratylenchus scribneri Scribner's Meadow
Nematode . First reported on potatoes in 1889 in
Tennessee. Associated with amaryllis, hibiscus,
strawberry in Florida, roses in California, and in
New Jersey, clover, corn, dahlia, orchids, pars-
nip, peach, potato, raspberry, rose, soybean, and
tomato.
Pratylenchus subpenetrans Described from
pasture grasses, Maryland.
Pratylenchus thornei Thorn's Meadow Nema-
tode . On wheat, other grains, and grasses. It has
also been reported on maple and nectarine.
Pratylenchus vulnus Walnut Meadow Nema-
tode . Described in 1951 from California as an
important parasite of walnut and rose on the West
Coast, also present elsewhere. It may affect avo-
cado, boxwood, almond, fig, forsythia,
gayfeather, apricot, citrus, peach, plum, rasp-
berry, loganberry, rose, sequoia, strawberry, Jap-
anese boxwood, spiny Greek juniper, blue rug
juniper, walnut, and yew. Soil fumigation has
increased growth of roses by 400 %.
Pratylenchus zeae Corn Meadow Nematode .
Associated with corn, also alfalfa, bean, chrysan-
themum, cucumber, grasses, pea, phlox, potato,
soybean, tobacco, and tomato.
Pratylenchus spp. Lesion Nematodes . Proba-
bly as widespread as a group as root-knot nema-
todes and even more serious, though less readily
recognized. The brown or black root condition
usually comes from secondary fungi entering and
rotting the roots after cells are pierced and torn by
the nematodes. In boxwood and other ornamen-
tals there is often a brush or witches' broom of
new surface roots to compensate for old roots
sloughed off. First symptoms are usually yellow,
black, or brown lesions on fine feeder roots. Box-
wood becomes sickly, stunted; foliage is dark
brown to orange, sometimes drops; some
branches may be killed. Tuberous begonias may
be heavily infested in roots and tubers, with poor

growth. Where possible, fumigate soil before
planting. Help plants to recover from root injury
by mulching, adequate watering, and feeding.

Radopholus

Pratylenchidae. Burrowing nematodes; endopar-
asites with entire life cycle inside plants, includ-
ing copulation and egg deposition. Male and
female wormlike, with short stylet. Female with
flat lip region, two ovaries; 0.6 mm long; male
with rounded lip region.
Radopholus similis Burrowing Nematode ,
Associated with SPREADING DECLINE OF
CITRUS. The most important citrus disease in
Florida. This is a subtropical species, first
reported in 1893 from banana roots in the Fiji
Islands. Citrus decline was known for many years
before the nematode connection was made in
1953. This species is also responsible for AVO-
CADO DECLINE and in 1963 was reported as
infesting 237 plants in many families. Possible
hosts include acanthus, allamanda, aluminum
plant, calathea, Barbados cherry, banana, castor-
bean, cocculus, hibiscus, Japanese boxwood, Jap-
anese persimmon, ixora, jacobinia, gingerlily,
loquat, Momordica , pandanus, peperomia, philo-
dendron, periwinkle, pothos, podocarpus, palms,
guava, as well as corn, pepper, tomato, and other
vegetables, and various trees. Asparagus, mari-
gold, and crotalaria are among the few nonhosts.
The burrowing nematode has been found in Lou-
isiana as well as central Florida.
The nematodes enter the cortical parenchyma
of young succulent roots just back of the tip and
form burrows, leaving behind avenues of infec-
tion for soil fungi and bacteria. Infected trees
seldom die outright, but have poor growth and
cease to produce a profitable crop. The disease
spreads in all directions from an infected speci-
men, but somewhat unevenly, the distance rang-
ing from 25 to 200 feet in a year, averaging about
50 feet. Long-distance spread is by transplants
from nurseries.
Control Living trees, once infected, cannot be
restored to vigor. Diseased trees in quarantined
areas are pulled and burned, including two trees