Issues of the week: July 7, 2010 — Spraying to prevent sclerotinia stem rot has begun, and flowering fields will move quickly through the spray window. Fields at 20% flower that have had moisture the past 10 days, have precipitation in the forecast, and have good yield potential and lush canopies are good candidates for a fungicide spray.
Sclerotinia management: 3 key points
The decision to spray petals to prevent sclerotinia stem rot depends on 3 key questions: 1) Have conditions been moist over the past few weeks for apothecia development and survival? 2) Is the canopy thick and is yield potential high? 3) Does the forecast call for more rain and/or humidity in the next week? If the answer is “yes” to …
Sclerotinia management: What is 20% flower?
Fungicide to protect the crop from sclerotinia stem rot infection must be applied to petals before infected petals start to drop into the canopy. Petal drop starts after 30% flower, so the best time to apply is at or just prior to 30% flowering to cover as many flowers as possible. This is assuming conditions have been suitable for spore …
Consider split application for multi-stage crop
If crop staging is widely variable and if fungicide is needed to prevent sclerotinia stem rot, a split application may be worthwhile. The first application can be made when the first plants reach recommended staging. If necessary, a second application can be made when the remaining plants are ready to be sprayed. Refer to current crop protection guides to determine …
Tips to control multiple insect species at once
If a field has cabbage seedpod weevil and diamondback moth feeding, should economic spray thresholds be reduced to account for the combined pressure? In the case of these two species, the answer is no. Count them separately and stick to the economic control thresholds for each. Why? Because weevils attack flowers and buds, but diamondback moth right now are eating …
Keep malathion out of canola bins
As bins are prepared for the coming harvest, keep in mind that using malathion on canola seed or in canola storage bins will result in detectable levels of malathion residue because malathion has a strong attraction to the oil in canola seed. Consequently, malathion can move into canola seed from storage bin walls. Detection of malathion residue in canola seed …
Insect threat builds
Issues of the week: June 30, 2010 — Lygus spraying starts in the Peace, cabbage seedpod weevil spraying starts in the southwestern Prairie, and we’re all on diamondback moth alert. Scout damage closely and spray only when necessary. With so many potential insect threats, multiple sprays are probably not economical. Oh, and don’t forget about sclerotinia.
Lygus spraying starts in Peace
Some Peace fields have 4-5 adults per sweep, prompting many farmers to spray at the bud stage. This is earlier than normally recommended, but with drought stress, canola may not be able to compensate for bud losses. Scout for signs of damage. Look for penetration marks at the base of the bud where adult lygus bugs are present. If …
Good conditions for sclerotinia stem rot
Spraying to prevent sclerotinia stem rot has started in Manitoba and many canola fields across the Prairies are coming into the spray window — 20% to 50% bloom. With good moisture and high humidity, growers with canola at early flower should use the checklist below to assess their sclerotinia stem rot risk. Fields scoring 40 or higher could benefit …
Watch for blackleg on leaves
Blackleg presence is higher than usual on canola in Manitoba and southeastern Saskatchewan. If you see grey lesions with black picnidia (peppery spots) on leaves, monitor the field. The variety may have adult resistance, so early infection on the leaves may not result in severe stem damage. Spraying is not likely economical. Blackleg can infect canola all season long, …