Paratrichodorus minor

Paratrichodorus minor	Contents	Rev 10/22/2008
	Classification	Hosts
	Morphology and Anatomy	Life Cycle
Return to Paratrichodorus Menu	Economic Importance	Damage
	Distribution	Management
Return to Trichodoridae Menu	Feeding	References
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Classification:

      Adenophorea
       Triplonchida
        Diphtherophorina
         Diphtherophoidea
          Trichodoridae
           Trichodorinae
             Paratrichodorus minor

Stubby Root Nematode

Synonyms: Name evolved from Trichodorus christiei to Paratrichodorus christiei to Paratrichodorus Nanidorus minor to Nanidorus minor (Rafael Rodriguez) to Paratrichodorus minor.

Morphology and Anatomy:

Nematode is 0.46 - 0.71 mm long.

Body configuration usually rounded at both ends.

Cuticle tends to swell in water and fixative when nematodes are killed.

Curved odontostyle with dorsal groove.

Females: Diovarial.

Males: Males are rare. Caudal alae present. Single testis.

Ref. Decraemer, W. 1996

P. minor moving to root tip feeding site.

Distribution:

Widely distributed in temperate to sub-tropical climates and is most prevalent and injurious in coarse-textured soils.

Widespread in U.S. on many hosts; Christie reports nematode inhabits Muck soils in Florida.

The species is common in warmer California vineyards even in the absence of weeds or other vegetation.

Rare in Europe.

First characterized by Christie and Perry (1951) as a migratory ectoparasite that feeds over the whole of the root surface, but usually close to the root tip, including the root cap, the meristematic region, and the region of elongation.

Nematode pierces epidermal cell walls and root hairs with rapid thrusts (10 per second).

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Hosts:

Wide host range including alfalfa, azalea, boysenberry, vegetables, corn, tomato, onion, wheat, sugarcane, rice, grasses, etc.

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Life Cycle:

Life cycle complete in 16-17 days at 86 F, 21-22 days at 72 F.

Temperature range: 68-95 F.

The life cycle of stubby-root nematodes is not well studied. Eggs of Paratrichodorus minor, hatch 53.3 ± 7.3 degree-days using a basal threshold of 10^º C (DD10C) after egg deposition. Second stage population peaks occurred at 28 DD10C , third stage at 67 DD10C , fourth stage at 109 DD10C and adults at 143 DD10C for adults. Population densities increased in the presence of a suitable host but declined to 33% of the initial level after 300 DD10C in the absence of a host (Schneider and Ferris, 1987).

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Damage:

Vectors California and Wisconsin isolates of Tobacco Rattle Virus.

Injurious to tomato and onion in the southeastern U.S.

Devitalizes root tips and stops root growth. Produces "coarse root" or "stubby root" symptoms. Injury caused by P. minor is deceptive because it often lacks discoloration, necrotic lesions, and other conditions usually associated with a disease, but there are few types of root injury that will affect the growth of a plant more quickly than devitalized root tips.

Paratrichodorus minor damage to corn

P. minor on St. Augustine grass: Nematode is a serious pathogen and economically important pest of St. Augustine grass (Stenotaphrum secundatum) in Florida and Georgia [Rhoades, H. 1962. Plant Disease Reporter 46:424-427; Heald, C.M. and V. G. Perry. 1969. Agronomy:358-369].

P. minor on sugarcane: Apt and Koike (1962a, 1962b) and Jensen et al. (1959) demonstrated the pathogenicity of this nematode to sugarcane. It caused severe stunting and prevented development of fine feeder roots of seedling sugarcane grown in pots. The tap root growth decreased in direct proportion to the number of nematodes present.

P. minor on cotton: Alhassan, S.A. and Hollis, J.P. (1966) (Phytopathology 56:573-574) Studied the effect of inoculum with 0, 100, 400, or 1600 nemas/pot in steamed soil on cotton plants (3 weeks old). Root tips were attacked, causing an overall reduction in size of root syustem. Top growth was stunted but no root necrosis was observed. Seedling weight was inversely related to both initial and final nematode density. At 1600 nematodes/plant, root systems were significantly reduced in weight, volume, area, and number of branch roots when compared to controls. High initial population gave slow increase -- low initial population (Pr) gave high final population (Pf). Around 80 P. minor/500 cc soil may cause measurable damage to young cotton seedlings in the field.

According to Sasser,: "Absence of necrosis suggests that the relationship of P. minor to the host is one of balanced parasitism."

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Management:

Nematicides are effective but not economical on many of the hosts. Stubby root nematode is sensitive to applications of nitrogenous fertilizers, manures, certain plant extracts, and to soil fumigation, but notably quick to return to a steady base population level that almost never exceeds 80 to 100/250 cm³ soil (McKenry, unpublished data).

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References:

Schneider, S.M., and H. Ferris. 1987. Stage-specific population development and fecundity of Paratrichodorus minor. Journal of Nematology 19:267-394.