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Top 10 sclerotinia stem rot questions
1. What is 20 per cent flower? For most fungicides, the window for application is from 20 to 50 per cent flower, with optimum timing typically around 30 per cent flower. At 20 per cent flower, the main stem will have 15 flowers. Consider that canola can reach 20 per cent flower within four or five days after first flower, and petal drop starts after 30 per cent flower. 2. When to spray an uneven crop? Count main stem flowers at a few sites in the field and take an average to come up with flowering stage for the field. For example, if you check 10 random plants and three or four are at 30 per cent flower and some have no flowers, the average is probably around 15 per cent. Split applications may be better if conditions indicate higher risk and the crop has a lot of plants at different stages. 3. How much moisture does the disease need? Moisture is the most important risk factor, and canopy conditions need to be moist starting three weeks before flowering and through flowering to cause disease. A really helpful a simple tool is the “wet pants test”, but it requires regular walks in the field. The full article provides a few more details plus the seven other questions.
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