After the weeks of incessant rain any dry days now will see the rapid release of further flushes of infective Phoma spores. The increased proportion of min-till drilled crops during the open autumn has left more surface trash and exposed cankers from last year’s oilseed rape crop to produce spores and prolong infection periods, warns Nick Watson of Syngenta.
"Heavy rainfall has damped down the movement of Phoma spores over recent weeks, but soil temperatures and wet conditions are highly conducive to further release and infection," he advises. "Crops that received any fungicide during the first infection flush in October are likely to need a second treatment of Plover now, to effectively top up protection and stop Phoma development through the winter months."
Mr Watson advocates any oilseed rape plants which have not yet been treated should receive urgent treatment as soon as leaf spots reach threshold levels. "Crops that were treated four to six weeks ago will still benefit from a second application, but there is greater flexibility in Plover application timing as conditions cool and Phoma movement on the leaf slows down."
Priority for treatment should be given to small leaved crops - where infection from leaf spots can quickly spread to stems - and the more susceptible varieties. "Keep a close eye for signs of leaf spots on newly emerged leaves," he adds. "Lesions on older leaves that are being naturally shed over the winter will have limited effect now, but infection on new leaves can continue to develop right through to the spring."
Plover has been shown to have stronger curative activity than some other autumn triazole options, as well as good control of Light Leaf Spot from applications right through to the spring. Where Light Leaf Spot is proving to be a major threat, however, Mr Watson advocates the addition of MBC with Plover as a cost effective treatment to boost control.
