(Cobb, 1917) Filipjev and Schuurmans-Stekhoven, 1941
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Widely, mainly in temperate regions, sandy soils.
pest in California Nematode Pest
Considered most economic important plant-parasitic nematode in
northeastern U.S. Readily spread in bulbs and rooted nursery
stock via irrigation water.
An example that characterizes some of the issues regarding migratory
endoparasitic nematodes is provided by the root lesion (Pratylenchus
penetrans) nematode problem of Easter lily bulbs in a relatively small
acreage of northwestern California and southwestern Oregon. Bulblets,
usually picked from a previous crop, are field-grown for 2 to 4 years until the
bulbs are large enough to sell to greenhouse operations for production of
flowering plants. Feeding by Pratylenchus penetrans on the roots retards
the rate of growth of bulbs and extends the time necessary for them to achieve
the 20-cm circumference used as a basis for marketing. If bulbs have not
reached 20 cm circumference in two years, they are replanted for one or two more
years (Hawkins, 1991; Westerdahl et al., 2003). Further, nematodes in root
tissues attached to bulbs are readily distributed throughout the state.
Avoidance of the lesion nematode
problem in Easter lilies by crop rotation or planting site selection is
difficult. The nematode has a very wide host range and is supported by the
pasture grasses that are commonly grown as an alternative to bulb production.
Many nematicides have been tested for nematode control in the region and
several have resulted in groundwater contamination. The current standard soil
treatment for management of P. penetrans in the region is a preplant
application of 1,3-dichloropropane (Telone II) at 428 kg/ha and 9 kg/ha of
Phorate applied at planting. Preplant drip applications of metam sodium or
emulsifiable 1,3-dichloropropene in combination with oxamyl or metalaxyl show
promise as a means of reducing the total amount of chemical applied to soil and
reducing the risk of groundwater contamination (Westerdahl, et al. 2003).
Potato Early Dying Disease is
caused by Verticiliiunm dahliae and exacerbated through interaction
with P. penetrans. The effect of
the nematode may be to:
provide entry points for the fungus by
feeding and endoparasitic migration.
reduce host defense mechanisms.
Although Verticillium and Pratylenchus are considered the main
causal agents in some potato growing areas of North America, other pathogens
such as the bacterium Erwinia and the fungus Colletotrichum
coccodes are associated with symptoms similar to
Potato Early Dying Disease.
Migratory endoparasite, mainly in root cortex but may enter
vascular tissues in later stages of infection.
350+ hosts, apple and cherry orchards, fruit trees, conifers,
Pest of lily bulbs (grown on 300 acres for bulb production) in
Del Norte County, CA.
Lily bulbs are rotated with dairy pasture which is also a host
to the nematode.
Sexually reproducing, males and females present.
Chromosome number n=12.
Eggs deposited in roots and soil.
The endosymbiont bacterium Wolbachia has been detected in
Pratylenchus penetrans. Ribosomal rRNA 16S similarity and presence of
homologs to all Wolbachia marker genes clearly placed the bacterium from P.
penetrans within the genus Wolbachia while phylogenomicanalysis placed
it at the base of the tree, suggesting that plant-parasitic nematodes were
the first hosts for Wolbachia.
The study suggests an earlier transition to mutualism before the
transition of Wolbachia to filarial nematode hosts. It is speculated that
mutualism of Wolbachia endosymbionts arosee through horizontal gene
Pratylenchus penetrans appears to obligately depend on its
Wolbachia endosymbions for survival, suggesting that mutualism is and
A question that remains is how obligate mutualism of Wolbacia arose in
filarial nematode hosts.
Necrotic lesions on peach roots after 24 hours. Symptoms of
debilitation above ground, including chlorosis and twig die-back.
Damage is increased by interaction with fungi.
Peach roots contain amygdalin (a cyanophoric ß-glucoside - essentially a
complex sugar with a cyanide molecule attached). Amygdalin is a
common constituent of Prunus spp., and is thought to be
hydrolyzed during a series of molecular events initiated by the plant in response to invasion.
The hydrolysis products of amygdalin are hydrogen cyanide and benzaldehyde which
are phytotoxic and result in cell death.
In a classical study, Mountain and Patrick (1959) found no amygdalin in root lesions
associated with P. penetrans; they
concluded that it is hydralyzed as either the plant invokes the defense mechanism against P.
penetrans or that the nematode initiates the
hydrolysis. They also found that necrosis and cell death in the root
tissue occurs rapidly following root invasion by the nematode and that it occurs
in advance of the invading nematode. An interpretation of thes
observations in light of current understanding of plant defense mechanisms is
that the plant is recognizing damage associated moleccular patterns (DAMPs) or
parasite/pathogen-associated molecular patterns (PAMPs) and initiating defenses
that result in cell death in advance of the invading nematode. In their
studies, Mountain and Patrick (1959) found that the necrosis could be initiated
by the nematode alone and did not require the presence of fungi or bacteria, but
that an imprtant contributor to peach replant problems by the nematode was that
root degeneration was accelerated by the infection courts for fungi and bacteria
that were provided by the damage.
Damage to lily bulb in Del Norte County
is a reduction in the rate of growth. Consequently, bulbs require
two years to reach marketable size rather than one year. Further,
harvested bulbs are infested with the endoparasitic nematode and will be
transported to new sites.
are effective on soil populations, but
have resulted in groundwater pollution in the sandy soils of Del
Chemical dips have been used for rooted material.
Hot water treatment at 45.5 C for 15 to 20 min kills
the nematode in apple roots, 48 C for 10 min in strawberry roots.
Hot water dips are also used to treat harvested lily bulbs, but the difference
between temperatures that kill nematodes an temperatures that cause damage to
flower bud primordia is quite small. Temperature regulation is critical.
Crop residues and organic amendments reduce
populations in apple orchards, either by breakdown products or by encouraging
growth of nematode-trapping fungi.
Treatment Thresholds. Severity of
Potato Early Dying is related to the inoculum levels of fungus and nematode
prior to planting. Damage threshold levels are Verticillium >
4 propagules /gm of dry soil in the absence of P. penetrans and 2
propagules/gm dry soil in the presence of P. penetrans
Host Plant Resistance, Non-hosts
Brown, A.M.V., S.K.Wasala, D.K. Howe, A.B. Peetz,
I. A. Zasada, D.R. Denver. 2016.Genomic evidence for plant-parasitic
nematodes as the earliest Wolbachia hosts . Scientific Reports | 6:34955 |
of Plant-parasitic Nematodes, Set 2, No. 25 (1973).
1991. IPM options for Easter lily bulb production: An overview. California
Department of Food and Agriculture. PM91-2.
Mountain, W.B. and Patrick, Z.A.
1959. The peach replant problem in Ontario: VII Pathogenticity of Pratylenchus
penetrans (Cobb, 1917) Filip. & Stek. 1941. Canadian Journal of Botany
D. Giraud, S. Etter, L.J. Riddle, J.D. Radewald, C.A. Anderson, and J. Darso.
2003. Management options for Pratylenchus penetrans in Easter lily.
Journal of Nematology 35:443-449.