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Copyright of Egyptian Journal of Agronematology is the property of Egyptian Society for Agronematology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surveys from 1986 to 1988 identified 22 phytoparasitic nematode species in Arkansas cotton fields. Meloidogyne spp. was found in ca. 15% of the fields sampled. Of these samples ca. 33% were found to have a population density of 106/100 cm(3) of soil or more. Rotylenchulus reniformis was found in high numbers (5,000 +/100 cm(3) of soil) in 1% of the fields sampled in 1988. Heterodera glycines was found in ca. 22% of the samples, presumably because of past cropping to soybean. Other common species found were Pratylenchus alleni, P. brachyurus, P. scribneri, Tylenchorhynchus ewingi, T. goffarti, Quinisulcius acutus, Helicotylenchus dihystera, H. pseudorobustus, Hoplolaimus magnistylus, Paratrichodorus minor, and Xiphinema americanum. Paratylenchus spp. juveniles were found in ca. 10% of the samples; adults of P. projectus and P. tenuicaudatus were found in ca. 1% of the samples. Other species found only rarely were Pratylenchus zeae, Merlinius brevidens, T. martini, Helicotylenchus multicinctus, Scutellonema brachyurum, and X. chambersi.

Field experiments were conducted in 1982 and 1983 to assess interactions between Heterodera glycines and Pratylenchus scribneri on soybean in southern Illinois. Soybean cyst nematode susceptible cultivar Williams 79 and resistant cultivar Fayette were treated or not treated with aldicarb 15G. Initial population densities were 35 H. glycines cysts containing eggs, 100 P. scribneri, 30 Helicotylenchus pseudorobustus, 225 Paratylenchus projectus, and 85 Tylenchorhynchus martini per 250 cm(3) soil in 1982, whereas in 1983 populations were 11 H. glycines cysts, 330 P. scribneri, and 620 H. pseudorobustus. In both years H. glycines populations increased on nontreated Williams 79, decreased on both treated and nontreated Fayette, and remained at initial levels on treated Williams 79. Recovery of P. scribneri per gram dry root was different between nontreated cultivars in 1982 but not in 1983. Aldicarb treatment suppressed soil and root populations of P. scribneri on both cultivars in both years. Populations of H. pseudorobustus, P. projectus, and T. martini at harvest indicated little population increase on either nontreated cultivar. In 1982 H. glycines caused yield suppression but P. scribneri did not, as differences in yield occurred between cultivars but not between aldicarb treatments. In 1983, however, there were no yield differences between cultivars, but aldicarb application resulted in yield increase in both cultivars. In 1983 the yield increase resulting from P. scribneri control was approximately 25%. No synergistic effect on yield was observed between H. glycines and P. scribneri.

Comparisons of plant parasitic nematode populations using a resemblance equation and community ordination showed that community structure tends to be similar on dark-colored, highly productive soybean soils throughout Indiana and Illinois. On lighter-colored soils community structures differed somewhat from those of darker soils and from each other.

The influence of rotation crop species on population densities of ectoparasitic nematode species common to soybean and corn fields of the North-Central region of the USA was studied for 5 years in 16 field blocks rotated to corn, soybeans, oats, wheat, and forage mixtures. Each block was sampled each year between mid-July and mid-August. High populations of Helicotylenchus pseudorobustus were maintained in all crops, especially corn. Tylenchorhynchus martini and Xiphinema americanum also developed with all crops, but a second year of corn depressed densities of both species. Paratylenchus projectus densities were high on soybeans and on forage consisting primarily of legumes.

The effect of soil type on population densities of plant parasitic nematode species in 17 field blocks of four different soil types rotated to corn, soybeans, wheat, and forage mixtures was investigated during a generally droughty 5-year period. High densities of Helicotylenchus pseudorobustus were found in dark silty clay loams. Highest densities of Tylenchorhynchus acutus were also in one of the dark-colored silty clay loams. Light-colored silt loams favored development of Paratylenchus projectus, which developed poorly in the darker soils. Comparable densities of Xiphinema americanum were found in all soils and on all crops, regardless of soil type. Tylenchorhynchus martini, although present, did not build up in any of the soils. Populations of Pratylenchus species were generally low in the rotated blocks of all soil types.