Application of Crop Modeling for Sustainable Grape Production - A Three Year Project

		Project Leaders: John Mathewson, Nancy Janes, Rocky Mountain Association of Vitners and Viticulturalists (RMAVV), Palisade, CO Technical Advisors: Harold Larsen, Horst Caspari, Rod Sharp, CSU Western Colorado Research Center and Cooperative Extension Service, Grand Junction, CO Project Years: 2002, 2003, 2004

2002 Project Summary

First season experience with the available Gubler-Thomas and Kast powdery mildew models found that neither model tracked powdery mildew disease development in the study vineyards with extremely close match. The Kast model was the closest, but it is likely that adjustment of the models may be required to obtain a close fit with actual disease observations through the season. However, the reduction of number of control sprays from six in the grower standard program to only three in the model-driven program demonstrates the potential value of the concept for control of powdery mildew in Colorado vineyards.

Click here for the full text of the 2002 Annual Report (Word Document).

2003 Project Summary

Initial incidence of grape powdery mildew in 2003 was detected belatedly and infection levels at one of the cooperating vineyards grew to severe levels before control was obtained. Control costs were higher as a consequence, and no substantial cost difference was found between the grower standard program and the integrated disease management program. Earlier detection might have provided opportunity for earlier control with lower cost control materials. Use of basal shoot leaves adjacent to the cordon arms might well provide an earlier detection of infection and will be incorporated into the detection program for 2004. Both the server and software have been upgraded so that "live" weather data from five vineyard sites are now accessible to growers via a dedicated web site.

Click here for the full text of the 2003 Annual Report (Word Document).

2004 Project Summary

Weather conditions in the spring of 2004 were the wettest April on record in the Grand Valley . Despite the wet April, as well as a rainfall in mid-May, no powdery mildew was found until mid-June in any of the monitored vineyards. The mildew from one field spread to all of the other vineyards but one. They were then sprayed accordingly.

This project has shown that grape powdery mildew can be effectively controlled with a spray program that is reactive rather than preventative in nature. Using such a program can lead to significant reductions in both spray applications and the costs for spraying materials. However, early detection of powdery mildew in critical for the success of any control strategy, including the integrated program.

Click here to see the 2004 Final Report (Word document) for "Application of Crop Modeling for Sustainable Grape Production".