Results of spraying and dusting potatoes for late blight

Summary

• 1. Four copper and four organic fungicides were tested against late blight of potato in Prince Edward Island during 1948 under severe epiphytotic conditions.

• 2. Phygon XL gave outstanding control of late blight on the foliage, and in this respect it was followed closely by Parzate. The four copper fungicides, Bordeaux (4-2-40), Bordow, C. O. C. S. Niatox, and Deecop, controlled the disease in the order listed, and were more effective than Dithane. Fungicide 629 gave almost no control.

• 3. It was evident that Phygon XL delayed the maturity of the plants.

• 4. All plots treated with fungicides except those treated with Fungicide 629 gave yields significantly higher than the check plots at the 5 per cent level. The yield resulting from the use of C.O.C.S. Niatox was significantly higher than the check plot at the 1 per cent level.

• 5. Three copper fungicides were applied in both dust and spray form.

• 6. Spraying was superior to dusting with regard to both yield and disease control.