Information system design for the rationalisation of fungicide use : the control of Puccinia hordei Otth

Abstract

Considerable scope exists for the reduction of the primary and secondary costs associated with crop protection, by the formulation of judicious fungicide application regimes. The design, building and operation of a farm-level computer-based information system is described, the purpose of which is to help the farmer make rational spraying decisions. The system makes use of a simulation model built in 1978 which is capable of accurate prediction of the yield loss induced by epidemics of Puccinia hordei Otth on Hordeum vulgare L. cv. Zephyr. Extensions were made to this model to enable crop growth and disease to be projected into the future. Increased disease intensity occurs in response primarily to certain meteorological conditions; a model was built to carry out the probabilistic simulation of key weather variables.

The Bayesian revision of yield reduction probability distributions provides the conceptual basis for the information system. The two strategies open to a decision maker as the season proceeds, those of spraying immediately and delaying application, were assessed using various decision criteria. Validation work was performed. Risk attitudes for a small sample of cereal growers were investigated; the importance of risk in the spraying decision is shown to be marginal. A low-cost method of implementation is illustrated; decision tables are derived on the basis of extensive simular experimentation and representative attitudes to risk.

It is concluded that such an information system has the potential for the provision of timely recommendations. Areas for further research are identified; an. information system incorporating the major diseases of cereals in Canterbury is conceptualised, built around a general disease/crop skeleton model.