TABLE CONTENTS

TOPIC TWENTY-ONE – COMMUNICATION AND EXTENSION
Do Current Crop Growth Models Allow for Nematode Damage?
Berry, S.D. (1), S. Sala (2) & M. Jones (1)
(1) South African Sugarcane Research Institute, 170 Flanders Drive, Mount Edgecombe, 4300, South Africa; (2)
ISTOM, Ecole d’Ingenieur d’Agro-Developpement International, 32, Boulevard du Port, 95094, Cergy-
Pontoise, France.
With the rise of computer technology, modelling has become a useful tool for many fields of
scientific research. Canegro, a crop growth model specific to sugarcane, has been under
development at SASRI since the early 1990’s, and simulates potential plant growth and
development under various climatic conditions. The current model incorporates weather data
and soil physical characteristics to simulate the growth and phenology of sugarcane. The
model does not simulate several other yield-limiting factors such as the effects of weeds,
flowering, nutritional deficiencies, ratoon yield decline and pests and diseases. Among the
pests of sugarcane in South Africa, plant parasitic nematodes are a major limiting factor for
sugarcane production, particularly on the sandy soils. The main species associated with
sugarcane damage are Meloidogyne javanica, Pratylenchus zeae and Xiphinema elongatum.
Results shown here are from initial attempts to quantify the differences between yields
simulated on Canegro and actual yields from field trials, with and without nematicide
(aldicarb) application.
Data were collected for two cultivars from five cultivar x nematicide trials, representing 98
datasets. In these field trials, nematodes were controlled in half the plots. No other major
pests and diseases were evident. Results showed that, in the control plots, the actual yields
were 48% (+/- 16%) of that of the modelled yields. When nematicide was applied, the yields
increased to 64% (+/- 17%). But at some sites, particularly where responses to nematicide
were high, the average dropped to only 20% (+/- 3%) of the simulated yields.
To better integrate the ‘nematode effect’ into Canegro, more systematic measurements, such
as crop growth (above- and below-ground), changes in nematode communities and
differences in soil properties need to be collected and evaluated.
5 th International Congress of Nematology, 2008 336