Quantitative reproductive potential of Heterodera schachtii on weeds typical for late summer fallow in sugar beet rotations
In Europe, sugar beet is often produced in a 3-year rotation with cereals, leaving stubble fields fallow from cereal harvest until primary tillage in autumn in the year prior to sugar beet production. The weed flora on such fields could include host plants of Heterodera schachtii that is one of the most important pests of sugar beet. Crop sequences with non-hosts and cover cropping with resistant cruciferous hosts during this period have been crucial for its management. Availability of resistant and tolerant sugar beet cultivars could entice growers to forego cover cropping, exacerbating weed problems during the fallow period. The objective of this study was to determine the reproductive potential of H. schachtii on weeds that develop during this period. Under glasshouse conditions, reproduction on 39 plant species was compared with that on oilseed radish and sugar beet of differing nematode host status. In 2 years in field microplots, 18 previously tested species were grown in H. schachtii-infested soil during the typical fallow period at 60 plants m−2, and nine of these species were also grown at 180 plants m−2. There were variable results between years after 8 weeks of growth, but most weeds allowed lower reproduction (<10%) than the susceptible sugar beet; only Stellaria media at 180 plants m−2 and Thlaspi arvense at both plant densities increased nematodes. Such weed densities may seldom occur under commercial conditions; thus, weed management for nematological considerations during the stubble period may have limited importance.
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