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Comparative Nematicidal Control of Heterodera schachtii on Sugar Beet as Affected by Soil Temperature and Soil Type. G. D. Griffin, Nematologist, USDA-ARS, Forage and Range Research Laboratory, Utah State University, Logan 84322-6300. . Plant Dis. 72:617-621. Accepted for publication 10 February 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/PD-72-0617.

Aldicarb at 4.5 kg a.i./ha and terbufos at 9.0 kg a.i./ha were most effective in increasing sugar beet root yields in Heterodera schachtii infested soil at population densities (Pi) of 2.8 and 4.9 eggs/cm3 of soil. They became less effective at Pi of 7.2 and 12.9 eggs/cm3 of soil, and there was a negative correlation between root yields and Pi. Root yields from aldicarb (4.5 kg a.i./ha) applied 7.6 cm and 15.2 cm from the seed at time of planting did not differ significantly (P< 0.05). The greatest root yields from aldicarb at 9.0 kg a.i./ha was obtained when it was applied 15.2 cm from the seed; it was phytotoxic when applied at a distance of 7.6 cm. Terbufos was most effective when applied 7.6 cm from the seed. Root yield increases from oxamyl was moderate to poor and a rate of 9.0 kg a.i./ha was comparable to aldicarb only at the low Pi (2.8 eggs/cm3 of soil). The distance of oxamyl from the seed did not affect the degree of control. Aldicarb applied in a 13-cm-row band was most effective at a rate of 4.5 kg a.i./ha, because it was phytotoxic at 9.0 kg a.i./ha in a 13-cm band. Another experiment examined the nematicidal activity of aldicarb and terbufos with 1,3-dichloropropene (1,3-D), and how the nematode-nematicide-plant relationship is affected by soil temperature and soil type. The 1,3-D treatments effectively controlled H. schachtii and increased sugar beet root yields at Pi of 3.9, 7.7, and 12.8 eggs/cm3 of soil at soil planting temperatures of 6, 12, and 18 C. Aldicarb and terbufos effectively controlled Pi of 3.9 eggs/cm3 of soil at the three soil temperatures, but were less effective than 1,3-D in controlling H. schachtii at the higher Pi. Root yields from the 1,3-D treatments were significantly (P< 0.05) greater in sandy loam and loam soils than in a clay loam soil. Aldicarb and terbufos were less affected by soil type than was 1,3-D.

Keyword(s): nematode population density, sugar beet cyst nematode.