Heterodera schachtii
Schmidt, 1871
Sugar-beet cyst nematode
Photo Gallery- Utah
Photo Gallery- Wyoming
Female.  The white or pale yellow females of the sugar beet nematode are easily observed with the unaided eye as they lie attached to roots.  Typically they are lemon-shaped and usually vary from 0.5 to 0.8 mm in length, but some specimens may be smaller or larger.  Many individuals diverge from the typical form.  Usually the subcrystalline layer is a prominent feature, appearing as a white incrustation completely covering that part of the body protruding from the root.  A mucoid mass extruded from the vulval region surrounds the posterior end and is covered with adhering soil particles.  The subcrystalline layer and mucoid mass give the femle protection from mononchs and other predators.
     Eggs withn the body may vary from less than 10 to over 600, with an avage of 286 from 500 Utah specimens.  Most females eject some eggs into the mucoid mass before encystment occurs.  These may number from 1 to more than 200.  They play an important part in the life history because they hatch immediately, enter roots, and produce another generation.  Raski (1950) observed that eggs within mature females and newly formed cysts hatched immediately under favorable environmental conditions and completed the life cycle in about 30 days.  Rapid multiplication through several generations in a season makes it possible for a relatively small population remaining after a rotation to increase to enormous numbers before the end of the growing season.
     Cuticular markings of adult females and cysts are rugose, chaotic, short, zig-zag elements without order of arrangement.  Head region annulated, the terminal annule almost round, surmounted by a squarish labial plate.  Spear straight or slightly curved, averaging 26 u in length and bearing ovoid basal knobs.  Median esophageal bulb spheroid.  Basal portion of esophagus extended in lobelike glands reaching back over intestine.  In early stages of development the slender ovaries are coiled in the body cavity.  As egg production proceeds, they completely fill the body.  As Mulvey (1957) noted, the cervix is supported by a single band of muscles attached to the lateral regions.  Vagina sheaflike from a dorsal view, ending in a deeply cleft vulva.  Fenestrae average 45 u long.

Male.  The male begins to develop in much the same manner as the female.  It first becomes an elongated, cylindroid body slightly shorter than the length of the original larva from which it was formed.  The testis appears as a series of cells roughly arranged in rows, with the terminus reflexed.  From the indefinite mass of cells and granules surrounding the testis the male body gradually takes form, finally appearing as an obese wormlike organism flexed once within the cuticle.  From this third stage the male elongates until it is flexed three or four times within the greatly expanded larval cuticle.  It now possesses a well-developed spear with strong basal knobs and all other organs typical of nematodes of this sort.  Development takes place in the root cortex, and after the final moult the male emerges into the soil.
     In length the males usually range between 1.3 and 1.6 mm.  Annules of the lip region, three or four, including the labial disc.  Spear 25 to 28 u long, with strong basal knobs.  Lobes of esophageal glands extending back ventrally along the intestine.  Testis single, outstretched; spicula bidentate, resting on a slightly arcuate, troughlike gubernaculum.
     Larvae range from 450 to 500 u in length, with a general average of about 460 u as stated by Taylor (1957).  However, under- and oversize larvae are not unusual, depending no doubt on the suitability of the host and on natural variation.  Spear averaging about 25 u length, which usually is about the length of the hyaline portion of the tail.

Identification.  Morphological differences between Heterodera schachtii and its close relatives are difficult to demonstrate.  Taylor (1957) separates the species on the basis of average larval lengths in microns: schachtii, 460; glycines, 484; trifolii, 502; galeopsidis, 518.  While these measurements are no doubt diagnostic in most instances, the possibilities of variants within a species should not be overlooked.  The muscle band supporting the cervix of schachtii is a single one, while the muscle bands of the closely related trifolii are furcate at their attachments on the body wall (Mulvey, 1957).  This is an exceedingly difficult character to determine, except on very favorable specimens.  Franklin (1940) determined that the distal ends of the spicula are bidentate, a character which appears to be rather stable.  However, males of other species also have bidentate spicula.  The wide range of hosts for H. schachtii makes determination on the basis of hosts of doubtful value.
(Description- Thorne, 1961)
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