Given the delayed harvest, chances to drill oilseed rape (OSR) were limited this year. However, slug damage doesn’t seem to be an issue, for the most part.
But growers should be alert, especially in regard of crops that were drilled in September. If there are any signs of grazing, slug pellets should be applied as soon as possible.
Meanwhile, volunteer cereals and some grass weeds seem to be growing well and are competing with some rape crops.
If they haven’t already been treated, any of the approved graminicides, e.g., Falcon, Fusilade Max, can be applied now at three-quarters to a full rate, depending on the weed issue.
Where diseases of rape are concerned, phoma will be the main target of autumn fungicide applications.
However, crop however, varieties differ in their susceptibility. So growers follow the threshold guidelines for control (10% of plants affected).
In addition, this fungicide timing needs to be effective against both phoma and light leaf spot.
The choice of fungicide will often come down to whether or not the crop needs a growth regulator effect or not.
Backward or thin crops will not need a growth regulator, so an application of a half-rate prothioconazole (Proline) should be adequate.
In early-sown crops where a regulator is probably needed, options include metconazole-based products (Sirena, Plexeo) or tebuconazole-based products (Prosaro, Jade, Pontoon, Protendo), again at half the recommended rates.
OSR
According to Teagasc, plant disease specialist Dr. Steven Kildea, not seeing the actual presence of light leaf spot in OSR does not mean that the disease is absent within a specific crop.
Dr. Steven said: “This is particularly so in crops with large leaf covers. It’s a case of missing the small lesions. However, in smaller crops with smaller leaves, it’s that much easier to pick up on the lesions.
“We are talking about a wet weather disease. Temperatures were quite high over recent weeks, whereas light leaf spot tends to favour cooler conditions, when it comes to its spread throughout a crop.”
Recent years have seen the development of OSR varieties with a degree of resistance to light leaf spot.
“The greater the inherent levels of light leaf spot resistance that we can bring to bear, the more impactful will be the integrated pest control management systems that we can develop.
“Once light leaf spot gets going within a crop, it will produce a lot of inoculum,” he added.
Light leaf spot is a polycyclic disease. In other words, the fungus creating the disease can complete its entire life cycle a number of times within the same growing season.