Downy mildew is surprisingly one of the most common diseases of oilseed rape, appearing in the autumn and then building up on lower leaves in the spring during extension growth. This year it has been reported as being particularly widespread on many late-emerging crops. It is these crops which have less time to put on new growth before the winter dormant period that will be affected the most, says Dr. David Stormonth, Technical Manager of Interfarm UK Ltd.
"This autumn the delayed harvest has meant a later than normal sowing period for winter oilseed rape and the moist, warm conditions have encouraged downy mildew infections. In the autumn, downy mildew causes yellowing of leaves and cotyledons which can become bleached with age. You can also usually see white spore-bearing structures on lower leaf surfaces. Action is required immediately to prevent further spread in the many late-drilled rape crops. The treatment is simple and inexpensive, involving the use of Quell Flo (mancozeb). Quell also shows useful activity on other oilseed rape diseases such as Phoma and light leaf spot, both of which can cause more damage in small, slow growing crop which are all too common this year," says David.
"In addition to disease control, Quell Flo applied at 1.5 l/ha delivers 140 gms/ha of elemental manganese which will improve green leaf production and retention, leading to a healthier crop. This is a significant nutritional dose which will help to improve canopy colour and management. Better canopy management in the autumn will also help to improve root development and reduce landing sites for pigeons. Also greener crops tend to attract fewer aphids. When fertilisers are escalating in price, this extra nutrition will be welcomed."
According to Dr. Stormonth, Quell Flo reduces the likelihood of fungicide resistance development. "Using Quell as aprt of the overall disease control programme this autumn is a responsible approach that will ensure that disease resistance does not become such a widespread problem in oilseed rape, as it already is in many other arable crops."
"Quell Flo can be tank-mixed with the major triazole fungicides such as difenoconazole, flusilazole, flusilazole + mbc, tebuconazole, metconazole, prochloraz, prothioconazole and prothioconazole + tebuconazole. It is also compatible with pyrethoids, propyzamide products and most graminicides," concludes Dr. Stormonth.
Quell Flo contains 455g/L mancozeb formulated as a suspension concentrate and packed in 10 litre containers. It has label approvals for use in winter oilseed rape, winter wheat, spring wheat and potatoes. In oilseed rape it recommended at a dose rate of 1.5 l/ha in 200 litre/ha for good coverage. It can be applied up to the end of December in the year of sowing. It has no LERAP and is rainfast in one hour.
For further information, please contact Dr. David Stormonth, Technical Manager, Interfarm UK Ltd. on 01354 741414 or 07818 036506 (mobile) or via e-mail david.stormonth@interfarm.co.uk
