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Demonstration of an Effective IPM Program for Fungal Leaf Blight Diseases of Carrots 1999

Project Leader: George Abawi

Objectives:

1. Demonstrate an effective scouting procedure for assessing the critical threshold level for scheduling the first fungicide application against fungal leaf blights on carrots.

2. Determine and demonstrate the need for additional sprays, if any, by monitoring disease severity and utilizing available weather forecast data.

Results:

The data confirmed the validity of the threshold level of 25% infected leaves as the trigger for the first application of fungicide to effectively control leaf blight of carrots. The first application of fungicide to the IPM plots was made only after this threshold level was reached, yet disease incidence and severity was no higher in these plots than in the grower- managed plots. The methods used to assess the need for subsequent treatments for leaf blight were monitoring of disease development, using local weather forecast information, and allowing a minimum of 10-14 days between sprays. Fewer sprays were applied to the IPM plots than to the grower-managed plots as a result of the scouting program. Carrot cultivars differed greatly in their tolerance to leaf blight, with lowest disease incidence and severity on ‘Fullback’ and ‘Carson’ and highest incidence and severity on ‘Eagle.’