20 March 1998

Time is ripe to put the brakes on forward rape

LUSH forward rape crops could benefit from a plant growth regulator to reduce canopy height, increase stem strength and increase yield.

"Growth regulators should have a good effect on the forward crops we have this year," says ADASs John Spink.

Folicur (tebuconazole) sprayed at stem extension on a crop already well protected against disease gave the greatest growth regulatory effect of four triazoles and three growth regulators evaluated in trials at ADAS Rosemaund and Nottingham University in 1996.

Yield was 4.5t/ha (36cwt/acre), 0.6t/ha (5cwt/acre) higher than the next best treatment (Arable, Jan 16).

"Crops can have too many pods," says Mr Spink. "The increased shading of the taller crops increases pod and seed abortion, causing lower yields. Delaying spring growth in forward crops reduces pod numbers, but increases yield."

Growth regulation

Norfolk grower Robert Garner has exploited the growth regulatory effects of Folicur for three years and plans the same for this years 50ha (124 acres) of Apex and 17ha (41 acres) of Pronto.

"We direct combine, so reduced straw height is a big benefit. On average crops are 6in shorter where we use Folicur, but in extreme cases this can be as much as 9in."

His programme uses 0.5 litres/ha of Folicur at rapid stem extension. "Crops are just starting to move, so well be on in the next 10 days," Mr Garner said earlier this week. An untreated control strip is left to monitor effects.

Manufacturer Bayer recommends a full rate of 1 litre/ha or a half rate with 1.5 litre/ha of 5c Cycocel. "But time is running out for Cycocel," warns Bob Simons of Bayer. "For many crops in the south, the latest safe application of Cycocel – before yellow buds visible – has already past."