12 September 1997

Fast emerging rape needs watchful eye

AS newly-sown oilseed rape emerges and grows away rapidly, growers are being urged to monitor weeds, pests, and diseases closely.

The flying start has encouraged volunteer cereals to emerge rapidly, with spraying already under way, says Keith Dawson of CSC Cropcare. Falcon (propaquizafop) is favoured for its additional control of meadow grass and couch.

Barley volunteers are a big problem in some fields this year, especially where high screenings crops were combined without chaff spreaders, says Richard Elsdon of United Oilseeds.

Quick growth means some growers will have missed pre-emergence herbicide timings, he adds. "Butisan may have to be delayed until crops have one true leaf."

Crops should grow away from slug problems if soils stay moist and warm, he adds. "Many will have two true leaves by mid-September, and will be getting slug-proof."

However, mild weather will encourage cabbage stem flea beetle, he warns. "They will come out from hedges pretty quickly." Crops struggling from shot-holing should be treated with a pyrethroid, with a follow-up treatment likely to be needed in October to control larvae.

Disease also needs monitoring. "Many crops will emerge before last years debris has been ploughed down, allowing light leaf spot and phoma to start earlier." Affected crops should be sprayed with a half-rate triazole towards the end of October, he advises.

Aggressive crops should stifle competitors. A spring tidy up may be all that is needed, says Mr Elsdon.

Direct-drilled crops will need 20-40kg/ha of N as soon as possible to encourage growth. "Soil disturbance will be minimal, so there will have been no mineralisation of nitrogen. Crops planted in mid-September will also benefit, he adds.n

OSRMANAGEMENT

&#8226 Most crops drilled.

&#8226 Good, moist seed-beds.

&#8226 Rapid emergence.

&#8226 Many pre-em sprays missed.

&#8226 Volunteer spraying under way.

&#8226 Flea beetle arracks reported.

&#8226 Disease likely, including light leaf spot.