RELATIONSHIPS OF INITIAL POPULATION-DENSITIES OF MELOIDOGYNE-INCOGNITA AND MELOIDOGYNE-HAPLA TO YIELD OF TOMATO

  • 1 January 1976
    • journal article
    • research article
    • Vol. 8  (3) , 232-239
Abstract
Microplots 80 x 100 cm, infested with varying initial population densities (Pi) of M. incognita or M. hapla, were planted to tomato [Lycopersicon esculentum] at 2 locations. Experiments were conducted in a sandy loam soil at Fletcher, North Carolina [USA], (mountains) where the mean temperature for May-Sept. is 20.7.degree. C, and in a loamy sand at Clayton, N.C. (coastal plain) where the mean temperature for May-Sept. is 24.8.degree. C. In these experimentally infested plots, M. incognita and M. hapla caused maximum yield losses of 20-30% at the mountain site with Pi of 0-12,500 eggs and larvae/500 cm3 of soil. In the coastal plain, M. incognita suppressed yields up to 85%, and M. hapla suppressed yields up to 50% in comparison with the non-infested control. A part of the high losses at this site apparently was due to M. incognita predisposing tomato to the early blight fungus [Alternaria solani]. In a 2nd experiment, in which a nematocide was used to obtain a range of Pis (with Pi as high as 25,000/50 cm3 of soil) at Fletcher, losses due to M. incognita were as great as 50%, but similar densities of M. hapla suppressed yields by only 10-25%. Approximate threshold densities for both species ranged 500-1000 larvae and eggs (higher for surviving larvae) for the mountain site; numbers as low as 20 larvae/500 cm3 of soil of either species caused significant damage in the coastal plain. Chemical soil treatments proved useful in obtaining various initial population densities; problems were encountered in measuring effective inoculum after such treatments, especially in the heavier soil.

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