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Crop & Food Research has developed a model to forecast the occurrence of severe barley yellow dwarf virus (BYDV) incidence in autumn-sown wheat crops in Canterbury based on alate aphid flights. This information is potentially valuable to growers in Canterbury, who can modify their inputs each year according to the risk of BYDV. This paper uses expected gross margins to estimate the financial benefit of the Crop & Food Research BYDV Forecast Service to arable growers in Canterbury. Results suggest that the value of the BYDV Forecast Service is positive, but varies greatly depending upon forecast accuracy and adoption rate.

A postal survey of 700 Canterbury arable farmers was undertaken during August/September 1998 to ascertain the importance of yellow dwarf viruses (YDV) in autumn sown cereal crops. The survey also sought to document farmers' practices for YDV management and the use to which they put the aphid monitoring and virus forecasting system provided by Crop & Food Research as well as their opinions on its effectiveness. The response rate was 24%. Most farmers had experienced YDV although for many it was not a recent problem. Many farmers employed more than one strategy for YDV management, the most common being to sow late or apply preventative insecticides to control aphid vectors of these viruses. The monitoring information had been seen by over 80% of respondents, and was judged as a good or satisfactory use of levy funds by over 92%. Information from the aphid monitoring virus forecasting system was used as an aid in the decision making process for YDV management.

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