Early autumnal temperatures well above the seasonal norm have been excellent for strong oilseed rape establishment in good soil conditions, but it has also been perfect conditions for insect pest activity. Most crops have signs of beetle feeding damage and aphid activity, along with many crops in the south even suffering attacks from Turnip Saw Fly Larvae.
With many crops now reaching over six weeks since sowing, the beneficial effects of insecticidal seed treatments are being stretched, warned Syngenta Field Technical Manager, Simon Roberts. “Whilst most farms are incredibly busy with establishing wheat, oilseed rape growers must still be vigilant for early signs of pest activity, and prepared to act quickly,” he advised.
Mr Roberts advocated control of Flea Beetle and stopping damage by most other insect pests would be best achieved with an application of fast-acting Hallmark Zeon. “That would also control most aphids, except where pyrethroid-resistant Myzus persicae are present. Where resistant Myzus are suspected, growers would have to switch to Plenum.”
Control of Myzus persicae is especially important, since it is the primary vector of Turnip Yellows Virus (TuYV) that can reduce oilseed rape yields by up to 30%. Early season virus infection is likely to lead to greater yield losses. Monitoring of aphid populations has revealed numbers of pyrethroid-resistant Myzus have increased significantly over recent months. Plenum effectively controls all aphid species, to minimise the spread of virus and stop further damage.
Most well grown oilseed rape crops should now avoid the worst of damage from Flea Beetle feeding activity. “However, any later emerging seedlings could still be hit, and the damage from the characteristic ‘shot-holing’ of leaves puts plants under additional stress that could make them more susceptible to other problems,” he advised.
“Establishing strong, compact plants with good root systems now, will give the potential to drive up oilseed rape yields in the spring.”
Mr Roberts added that autumn applications of either Hallmark Zeon or Plenum could be combined with control of volunteer cereals and grassweeds when using Fusilade Max, or with Plover treatments for Phoma and Light Leaf Spot.