Question 2: What conditions promote high disease severity? Moisture is the key factor. “Prevalence of sclerotinia has a direct correlation to above-average moisture,” Jurke says, which is why three moist years in southwest Saskatchewan led to a jump in severity. Good soil moisture and a few rains in the period starting two weeks before flowering and carrying through to infection after flowering will greatly increase sclerotinia stem rot severity. Sclerotia, the resting bodies in the soil, need moisture to germinate into apothecia, the tiny mushrooms that produce ascospores that shoot up into the canopy. Apothecia then need about two weeks to grow and release spores, which is why moist soils in the two weeks before flowering will lead to more serious infection. After that, rain or even just heavy dew and high humidity are needed for infection and lesion growth. A field with a canopy to produce a 30 bu./ac. or better crop tends to have a more humid microclimate and increased risk for disease. Plus, a field with this yield potential will increase the return on investment for a fungicide spray. Question 3: What can growers do to manage the disease? Growing sclerotinia-tolerant varieties may reduce infection levels, but with favourable moisture, fungicide will often provide a return on investment even when these varieties are grown.
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Sclerotinia stem rot produces a bleached or tan lesion on the stem.
Sclerotinia stem rot or blackleg? Pre-harvest is a good time to assess disease severity because diseases are easiest to identify at this stage. With careful scouting, growers can identify which diseases are present, estimate yield loss and consider whether — in hindsight — a fungicide spray would have been a good idea. Sclerotinia stem rot and blackleg are two important canola diseases to look for at harvest. Here’s how to tell them apart: Sclerotinia stem rot — Look for areas in the field with lodged or prematurely ripened plants. — Examine the basal (bottom) to middle of the stem. Sclerotinia stem rot produces a bleached or tan lesion on the stem. With very high moisture and humidity, white downy growth appears on green stems, and as the stem dries, it will be bleached or brown (like a bone) and shreds easily when twisted by hand. — Hard, black sclerotia bodies (typically similar in appearance of mouse droppings but larger) can be found inside the stem or on the ground near the stem. Blackleg — Look for areas in the field with lodged or prematurely ripened plants. — Examine the basal (bottom) to middle of the stem. When blackleg is severe enough to cause yield loss, the plant will often have irregular, knotty, woody cankers at the base of the stem. Clipping stems is the surest way to make a positive identification. — Black pepper specks (picnidia) may appear within the lesions. — This infection will eventually grow through the stem, cutting off nutrient flow. If you see plants drying up, cut a few open to check. Use clippers to slice through the stem at the base or through the canker to determine if black discolouration is present within the stem. If more than half the area of the stem is blackened by the fungus, plant yield was likely reduced.
Working together to improve weed management Managing tough-to-control and other key, potentially resistant weeds can be a challenge. The best way to meet that challenge is to optimize weed control by tank mixing Roundup® agricultural herbicides with HEAT® herbicide in your pre-seed burnoff or chemfallow treatment. See your retailer for details.
SAVE $0.50/ACRE*
on Eligible Roundup® agricultural herbicides when purchased with matching acres of HEAT® herbicide.
For full offer details and to determine eligible products, go to www.rrwms.ca or www.roundup.ca. In addition to this discount, growers are also eligible for AgSolutions® AgSolutions Rewards on HEAT. For full reward details go to www.agsolutions.ca
* The Roundup agricultural herbicide and HEAT Offer off-invoice discount acres will be calculated using the following label rates: One case of HEAT= 640 acres (Jug of HEAT= 80 acres), Roundup Transorb HC and Roundup Ultra2 0.67L= 1 acre (10L= 15 acres, 115L= 172 acres, 450L= 675 acres, 800L= 1,200 acres). * Offer expires June 30, 2013. See your retailer for further details.ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Monsanto and vine design®, Roundup®, Roundup Transorb® and Roundup Ultra2® are registered trademarks of Monsanto Technology LLC, Monsanto Canada, Inc. licensee. AgSolutions is a registered trade-mark of BASF Corporation; the unique KIXOR X symbol is a trade-mark, and HEAT and KIXOR are registered trade-marks of BASF SE; all used with permission by BASF Canada Inc. © 2013 Monsanto Canada, Inc. and BASF Canada Inc. TANK MIXTURES: The applicable labeling for each product must be in the possession of the user at the time of application. Follow applicable use instructions, including application rates, precautions and restrictions of each product used in the tank mixture. Monsanto has not tested all tank mix product formulations for compatibility or performance other than specifically listed by brand name. Always predetermine the compatibility of tank mixtures by mixing small proportional quantities in advance. CROPS GUIDE
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