TOLERANCE LIMIT OF THE SUGARBEET TO HETERODERA-SCHACHTII

  • 1 January 1982
    • journal article
    • research article
    • Vol. 14  (2) , 199-202
Abstract
Field and greenhouse experiments showed that yield losses of sugar beet, B. vulgaris, did not occur in soil infested with fewer than 8 H. schachtii eggs/g soil. However, larger population densities greatly reduced sugar beet yield. In the field experiment, the yield in microplots inoculated with more than 64 eggs/g soil was less than 20% of yields in uninoculated microplots. Nevertheless, tolerance limits of 4 and 1.8 eggs/g soil, in greenhouse and field microplots, respectively, were derived by fitting the data with the equation y = m + (1 - m)zP-T [where y is the rate of the yield at density P and the yield at a density of P .ltoreq. T, m = the minimum relative yield (the yield at very large initial population densities), z = a constant < 1 and T the tolerance limit.] Maximum rates of multiplication of 55 and more than 300, and equilibrium densities of 340 and 130 eggs/g soil, were estimated in greenhouse and field microplot tests, respectively.