Four the week

Poor looking typical canola field 2014

Diagnosis: Ugly. A lot of canola crops are looking pretty sad, with small plants, low counts and a wide range of stages. This makes for difficult management decisions, including when to spray for sclerotinia stem rot — or whether to spray at all.

Late fungicide. The application window for fungicide to manage sclerotinia stem rot closes at 50% flower (or earlier for some fungicides). Early applications usually provide the highest return, but not always. Sprays late in the window can be effective.

Roots? Where? Discoloured splindly plants may be severed from their roots as a result of brown girdling root rot, foot rot and root maggots — which are at higher than usual levels this year, or so it seems. Rotation and brassica weed control are the best management steps.

Behold thresholds. You can find lots of insects in canola, but only a few are actual pests and canola can tolerate a reasonable number of them before spraying pays off. Consider the risk window and economic thresholds for each insect before making a decision to spray.