28 August 1998

Early treatment of oilseed rape can slash costs

Spray rape early if you want

to reduce herbicide bills

this autumn. That is the

message for growers keen

to erode production costs

still further this season.

Andrew Blake reports

WITH as much as half this autumns winter oilseed rape crop already sown, mainly into good seed-beds, growers are in a position to make useful savings on herbicide costs – provided they treat early.

John Taylor, regional manager for United Oilseeds in East Anglia, says: "Its certainly possible to spend £85/ha. But if you get in early enough you should be able to cut that quite a bit this year."

With few additions in the armoury this year, apart from Katamaran (metazachlor + quinmeric), the choice of products is much as last season, he notes.

"But there is plenty of moisture about, and good takes and early ground cover should reduce the need for herbicides."

In theory the vigour of hybrids, which currently account for 45% of sales in his area, offers good weed competition and may also encourage dose cutting. "But you must remember they are sown at a lower rate and tend to go in later than conventional varieties. So you are gambling on how well they get away to prevent the bigger gaps between plants getting filled with weeds."

The strength of some conventional varieties, notably Lipton, can also be exploited to cut inputs of products like Butisan (metazachlor), he suggests. "Where you normally use 1.5litres you might be able to make do with 1 litre or even just 0.75."

The way rape is established is also likely to influence programmes. "Where crops follow ploughing you can expect less competition from cereal volunteers."

Butisan, pre-emergence alone or with Treflan (trifluralin) at full rate 1.7-2.3litres/ha according to soil type, or Butisan post-em remain the most widely used southern options for tackling most broad-leaved weeds and suppressing grasses and volunteers.

"Incorporated Treflan on its own is cheaper. But its effect is quite short-lived so you are relying on the crop to get on top quickly."

Main broad-leaved targets continue to be cleavers and poppies, says Mr Taylor. "Trials suggest Katamaran offers better cleavers control than Butisan. But it is likely to be substantially more expensive.

"You dont always get a yield loss from cleavers, but they do cause problems in store. Poppies on light land can be very aggressive and crowd out the crop. The biggest mistake people make is not spraying soon enough.

"But all pre-emergence products go on when the crop is at its most sensitive and may cause damage, particularly if dry weather checks growth. Butisan pre-em on light land can damage the crop. It has got restrictions."

Consequently growers should do everything possible to ensure the crop gets away well, he advises. "Keep slugs out and give it a touch of N at the outset, say 30kg/ha as a base dressing, just to push it along. October is too late to be applying nitrogen."

The initial weed-killers should take care of a fair proportion of cleavers, he says. Follow up options include Galtak (benazolin) and Fortrol (cyanazine). "Fortrol is about half the price and is especially good on charlock.

"But chasing every last weed may prove false economy. Some people are accepting higher levels if they dont affect yield. It may be cheaper to dress out cleavers after harvest."

Further north, post-emergence Kerb (propyzamide) from October onwards remains a popular alternative to early treatment. "It works best in cool wet conditions, but has gaps in that it doesnt deal with mayweed, charlock or cleavers. You must expect to have to go back in the spring to control cleavers. In the south, Kerb is not so fashionable as it once was, but its big plus for growers with resistant blackgrass is that it brings in different chemistry."

RAPE WEED CONTROL

&#8226 Good moist seed-beds.

&#8226 Scope to trim herbicides.

&#8226 Ensure competing crop.

&#8226 Spray early rather than late.

GRASS WEEDS

Most crops require graminicides to control grass weeds and volunteer cereals, particularly barley which is more aggressive than wheat. There is a good range of weapons in Falcon (propaquizafop), Fusilade (fluazifop-P-butyl), Laser (cycloxydim) and Pilot (quizalofop-ethyl), says John Taylor, regional manager for East Anglia-based United Oilseeds.

For crops after wheat, Kerb may give adequate volunteer control. "But after barley you will probably need a reduced rate of a specific graminicide.

"Choice and dose depends very much on when you apply them and how big the targets are. All of them will struggle to control full size tillering wild oats.

"Broadly speaking Laser, with rates varying from 0.7 to 2.25litres/ha, does a good job, especially on wild oats." Fusilade is likely to be cheaper but weed knockdown tends to be slower, he notes. "Pilot is a bit cheaper still but not very effective on wild oats and like most of them less good on meadow grasses." For the latter he recommends Falcon. "Its more expensive but its also good against blackgrass."

Good conditions for rape establishment mean good weed control (left) is possible at less cost this autumn, says John Taylor, regional manager for United Oilseeds in East Anglia.