Impact of Nematodes on Sugarcane and the Benefit of Tolerant Varieties

The importance of growing sugarcane varieties that minimise losses from nematodes is linked to the effect that the nematodes have on the cane. Revised estimates of crop loss from nematodes in South Africa indicate a reduction in yield equivalent to more than 1.6 million tons cane per annum. The most pathogenic species on sugarcane, Meloidogyne javanica, is restricted to very sandy soils. The other pathogenic and much more widespread nematodes are Pratylenchus zeae, Xiphinema elongatum and species of Paratrichodorus. The varieties generally tolerant of these nematodes can be identified by their smaller response to treatment with nematicide. The contribution that tolerant varieties make in minimising losses from nematodes was quantified by comparing their yield with susceptible varieties in six field trials conducted on sandy soil in three regions of the sugar industry, with between three and six crops per trial. Where a nematicide was not used, growing a tolerant variety increased yields by between 25 and 124% (average 83%) over that of a susceptible variety. The benefit was broadly equivalent to the increased yield achieved by treating the susceptible variety with a nematicide. In the six trials this represented an average increase of 34 t cane/ha. It is also shown that nematode tolerant varieties can sustain yields over time through the continued production of high yielding ratoon crops.