When to Treat

I live in Chico, California. About six years ago I planted four Syrah vines to cover a 35 x 10 pergola attached to my house. As a side benefit to the shade I'm getting around four gallons of finished wine each year. In 2013 I lost the entire crop to powdery mildew, last year I treated the pm with powdered sulphur and later treated for white fly with Ortho Fruit and Vegetable insecticide. In both cases I waited until I noticed the problem before treating. (I also tried the powdered milk idea with no success.) I also planted six petite Syrah vines last year.

Knowing that I faced both problems last year, when should I begin treatment on each problem. And, should I treat the new vines too?

thanks

What you are using is a preventative spray. Once you have the problem, it is too late for the spray to provide protection. The spray needs to be there before you get the disease or insect pests to be effective.

Last year, I applied the sulphur as soon as fruit started to develop, about this time (May), and I didn't see any powdery mildew. As to the whitefly, it just popped up, mostly after harvest. I'm not sure what caused the pest issue and whether the Ortho is appropriate prior to harvest.