Rev 11/18/2025
Tylenchina Tylenchoidea Hoplolaimidae Hoplolaiminae Hoplolaimus seinhorsti Luc, 1958
Female: Length 1.0-1.48 mm.
Body cylindrical, slightly tapering towards front end; curved ventrally into an open circle when relaxed by gradual heating.
Cuticle distinctly striated; annules almost 2 um wide at midbody; subcuticular striation prominent, 2 striae for each annule.
Lip region hemispherical, set off from body by a deep constriction, usually with 4 annules; as many as 6 annules may be present. Basal annule of lip region with 8 to 12 longitudinal striations.
Labial framework well-developed and sclerotized, displaying a yellow color, outer margins extending backward for a distance of 3.5 annules.
Lateral fields reduced, represented by a single incisure on body, but often indistinct.
Phasmids large, 4 or 5 um in diameter, very refractive, anterior one at 26 to 44%, posterior one at 74 to 90% of body length from anterior end; anterior and posterior phasmid may be situated on either side of body.
Excretory pore 109 to 145 um from anterior end of body, usually opposite level of nerve ring or isthmus.
Hemizonid 7 um long, situated 5 to 21 annules posterior to excretory pore.
Hemizonion 5 to 10 annules posterior to hemizonid; hemizonid and hemizonion often appear as double structures at different levels in the body.
Stylet massive, well-developed, 40 to 49 um long, composed of two almost equal parts with large basal knobs; spear knobs with two blunt points on anterior margin separated by 2 or 3 small teeth, the latter often indistinct.
Orifice of dorsal esophageal gland close to base of stylet, 4 or 5 um behind spear knobs
Esophagus typical of the genus; median bulb oval, occupying about half of the body diameter, situated at 44 to 50% of the esophageal length.
Dorsal esophageal gland with 4 nuclei, overlaps the intestine dorsally; the 2 uni-nucleate subventral glands lie dorsolaterally and are variable in length; total of 6 nuclei in the three glands
Intestine does not overlap rectum.
Vulva at midbody or slightly posterior. Epiptygma usually single, anterior or posterior, but sometimes double.
Gonads paired, opposed and outstretched; no spermatheca observed.
Tail shorter than anal body diameter, rounded, with 10 to 17 annules; striations encircling the tip are sometimes irregular.
Male: Unknown.
[Ref: CIH Descriptions of Plant-parasitic Nematodes, Set 6, No. 76 (1976)]
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Widely distributed in tropical and subtropical areas of Africa, India, Philippines, Thailand, and Indonesia. Originally described by Luc (1958) on cotton (Gossypium hirsutum cv Acala 4-42) in Madagascar.
An important pest of many hosts, both economic and as food sources.
Based on its damage potential, Hoplolaimus seinhorsti is an A-rated pest in California (Martin, 2025)
Feed both semi-endoparasitically and endoparasitically on a wiode range of plant species.
On cowpea, H. seinhorsti was found to be endoparasitic, mainly in the parenchymatous tissue of the root cortex and also in the cortex of root nodules.
In cotton roots, it was also found to be completely inside the cortical parenchyma (Luc, 1958).
Cotton, sugarcane, cowpea, sorghum, rice, corn, melon, many types of vegetables, coconut, and banana.
Ecophysiological Parameters:
Seeds of cowpea were germinated in a field plot in Nigeria naturally infested with H. seinhorsti. One week after germination, the roots contained all larval stages as well as eggs. Most nematodes were in the parenchymatous tissue of the root cortex, and browning of cells was evident immediately around individual nematodes.
The nematodes increased in the roots to a maximum of 1,110 individuals/root system after 5 weeks.
In the soil, the population increased from 100 to 3,800 individuals/liter of soil after 9 weeks (Bridge, 1973).
Endoparasitic migrations of nematodes can cause considerable mechanical damage to root cells.
Nematodes are mainly confined to lateral roots, and by the end of 9 weeks following germination of cowpea in field plot experiments, most lateral feeder roots were necrotic or missing.
Species of Hoplolaimus become attached to roots when they semi- or entirely penetrate the root tissues. Root systems are damaged as cells die and outer layers of the roots are sloughjed away.
In bentgrass, for example, infected plants appear dark in color with fewer or no feeder rootlets (Jagdale et al., 2022; Donald et al., 2013). Cotton plants infected by lance nematodes are subject to stunting, yellowing, and defoliation with greater severity when soil moisture is limiting. Of course, similar symtoms may result from infection of roots by various organisms, so detection and diagnosis of the cause is important to allow rationale management decisions.
Avoid spread by movement of plant material, nursery stock and contaminated soil and agriciultural equipment.
Host Plant Resistance, Non-hosts and Crop Rotation alternatives:
Chitambar, J. J., Westerdahl, B. B., and Subbotin, S. A. 2018. Plant Parasitic Nematodes in California Agriculture. In Subbotin, S., Chitambar J., (eds) Plant Parasitic Nematodes in Sustainable Agriculture of North America. Sustainability in Plant and Crop Protection. Springer, Cham
Donald, P.A., Holguin, C.M. and Agudelo, P.A., 2013. First report of lance nematode (Hoplolaimus magnistylus) on corn, soybean, and cotton in Tennessee. Plant Disease, 97(10), pp.1389-1389
Jagdale, G.B., Takbir Nugraha, G., Martin, K., Martinez-Espinoza, A.D. and Hajihassani, A., 2022. Occurrence of the lance nematode Hoplolaimus stephanus infecting bentgrass Agrostis stolonifera in Georgia, USA. Plant Health Progress, 23(2), pp.162-165
Luc M, 1958. Les nematodes et le fletrissement des cotonniers dans le Sud-Ouest de Madagascar. Coton Fibres Trop., 13:1-18.
Martin, H.J. 2025. California Pest Rating Proposal for Hoplolaimus seinhorsti Luc 1958, Lance Nematode. California Department of Food and Agriculture, Sacramento, California.
Van den Berg E. 1976. Hoplolaimus seinhorsti. CIH Descriptions of Plant-parasitic Nematodes, Set 6, No. 76 (1976)