High yielding varieties with low Phoma resistance need looking after
With the autumn of 2008 being one of many contrasts for oilseed rape, growers are being urged to keep monitoring their crops, particularly those with lower disease ratings, throughout the winter and early spring in order to take the right course of action for effective disease control, say BASF.
"This autumn has been one of significant contrasts for the oilseed rape crop. Some geographic areas have taken a significant hit in terms of the overall area drilled, whilst other areas have crops at varying stages of development. Some crops look good, others not so good. But as both Phoma and Light Leaf Spot are responsible for significant yield loss in rape, it is still important to keep looking at the crop to gauge its individual disease control needs and be prepared to act as and when necessary," says Will Reyer, newly appointed BASF Oilseed Rape Product Manager.
Will points out this is particularly so for varieties with weaker resistance to Phoma stem canker. "Overall there is a trend towards low to moderate resistance to Phoma in current varieties and also those on the new HGCA 2009/2010 list. The three top yielding varieties added to the list in 2009 have ratings of only 4 to 5 for Phoma. This means that most varieties will need close attention to help them reach their full potential."
"Using disease resistance together with a timely fungicide programme, autumn and spring, will be important as growers manage their crops and focus on maximizing yields. If you are growing susceptible varieties you may need to be even more focused on what to do next," says Mr. Reyer.
Dr. Peter Gladders, Plant Pathologist for ADAS, points out that Phoma is the main disease this year to date for those growers outside Scotland and the North, but it has developed slowly so far this autumn, rather like 2007. He has also found Light Leaf Spot in the North recently and with the current cold weather the risk of problems could be high. "Oilseed rape crops will still need regular monitoring for the leaf symptoms. In smaller crops you have got to keep chasing Phoma right up until February and keep checking plants, particularly susceptible varieties, in order to guide your next spray decision. This season with the wide variation of crops at different sizes, different approaches will be needed. Smaller plants can benefit from treatment up until stem extension and may need a T2 spray of a non PGR fungicide up until in Mid February."
"Normally we would expect to complete two Phoma sprays in the autumn, but ground and weather conditions are making it difficult to apply the autumn T2. Depending on how the conditions pan out over the winter, consideration of a PGR fungicide such as Caramba in the spring will be a good choice as it not only controls disease but also has a beneficial effect on root development and initiates canopy management."
For further comment and information please contact Will Reyer, BASF on 01614885490 or 07879 434433 or by email at William.reyer@basf.com
Background Notes - Caramba contains 60 g/l metconazole, formulated as a soluble concentrate and packed in 5-litre packs. It is recommended in winter oilseed rape, winter wheat, winter barley and spring barley, field beans and peas. Caramba is a broad-spectrum fungicide with curative and protectant activity. In oilseed rape, it can be applied as soon as diseases develop at a recommended maximum dose rate of 1.2 l/ha for Caramba in 200 litres of water. Caramba is subject to LERAP category B.
