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No spray / one spray / two sprays for sclerotinia?
Variable moisture and uneven crop staging may make the sclerotinia spray decision challenging this year. A fungicide is recommended if environmental factors leading up to and during flowering favour sclerotinia development, the pathogen is present in sufficient quantity, and yield potenial is high enough to justify the $20-$30/acre cost of application.
A simple way to appropriately time a single application in a variably staged crop is to count main stem flowers at multiple locations around the field to calculate an average flowering stage for the field. In many cases, the better option is to base timing on the portion of the crop that is most likely to produce the majority of the yield.
A split application may be preferable in a variably staged crop if both sclerotinia risk factors and yield potential are high. Applying first to more mature plants – even if most of the crop is less mature – can keep spore-infested petals from landing on pre-flowering plants. Reducing early infection on less mature plants can protect yield by ensuring those plants are not exposed to the disease for a long period. (Sclerotinia stem rot) (Factors in the sclerotinia spray decision) (Podcast – sclerotinia spray decision)
Is there ROI in that insecticide spray?
Insects of all kinds are now crawling and flying into canola fields. Effective insect management includes knowing when – and when not – to spray. Every spray decision should consider economic thresholds. Notable insects this week include:
- Alfalfa looper: there have been some reports of feeding. No economic thresholds are set for this pest, so use thresholds for bertha armyworms as a guideline. (Identify green worms accurately)
- Cabbage seedpod weevil: are moving into non-typical areas. Scout at 10-20% flower (approximately one week after first flower) using a sweep net. The economic threshold is 25-40 CSPW per 10 sweeps generally across the field. (Cabbage seedpod weevil scout and control tips)
- Bertha armyworm: heat and advanced growing degree days could mean earlier-than-usual arrival, though reports may also be mis-identified clover cutworm. Thresholds are the same for both insects. (Podcast: bertha armyworm)
Why isn’t my canola flowering normally?
The CCC has received multiple reports recently of canola not progressing through flowering normally. There are many reasons buds might not develop properly or plants might drop flowers. Any weather stress can trigger a hormone imbalance that leads to malformed growing points, abnormal bud and flower production, and sterile pods. Additionally:
- Temperatures above 28°C can cause shortened stamens;
- Drought can cause small and/or off-colour petals and dropped flowers;
- Nutrient deficiency can reduce flowering and/or can cause shortened stamens (boron) or pale, smaller flower petals (sulphur);
- Insect damage to buds (generally from lygus bugs and diamondback moths) can cause dark stains on flower petals and shriveled brown pedicles;
- Late off-label applications of herbicides, such as glyphosate applied after the 6-leaf stage, can cause pale petals and short stamens; and/or
- Frost / cold stress can burn flowers or delay flowering. Canola may suffer damage even when low temperatures stay marginally above zero if near-zero temperatures coincide with the stress of herbicide applied just before or just after the cold event.
The “mystery syndrome” or “floral deformation syndrome” found most often in weather-stressed canola is very likely the result of hormone imbalance. If you suspect floral deformation syndrome, please send photos and a description to your CCC agronomy specialist. (Many reasons for missing pods)
When does the next round of Canola 4R Advantage funding open?
The CCC is now accepting applications for year two of Canola 4R Advantage, which provides funding to help pay for best management practices (BMPs) focused on nitrogen management. Check out the demo video that reviews the new, user-friendly application portal and steps to complete an application: the video and link to the portal are available on the CCC website at canolacouncil.org/4r-advantage, along with complete program details including answers to common questions.
