30 October 1998

Spraying delays threaten cheap herbicide policy

Concerned to relaxed – that

is the range of reactions to

autumn weed-killing progress

on our barometer farms.

Andrew Blake reports

BAD weather delaying treatments leaves David Pettitt increasingly anxious that his relatively cheap cereal herbicide strategy may be in jeopardy. None of the isoproturon-based programme had been applied by last weekend.

Blackgrass is key target at West Hall Farm, Rickinghall. "Timing is my main concern," he says. "If we are not on fairly quickly with the isoproturon the blackgrass may get too large to control and we would have to consider alternatives like Hawk with big cost implications. ipu has come down a lot in price."

Most blackgrass on the farm still has only one leaf, notes agronomist Simon Draper. But mild conditions could soon see more. "I wouldnt want to chance ipu beyond the two-leaf stage. But Hawk would add another £3-4/acre, and with wheat prices as they are we have got to keep costs down."

In theory the farms 18m boom Amazone UF1200 sprayer with 800-litre front tank covers up to 90ha (220 acres) a day. But good days have been rare this autumn and the decision to drill second crop wheat later than usual to counter take-all has pushed the programme behind. "We certainly like to be done by the end of October."

With no known herbicide resistance he is reluctant to switch from the straightforward post-emergence treatment advised by Mr Draper.

"We try to keep it simple," says Mr Pettitt. "That approach has worked pretty well in the past two years which were quite dry, though this year is a different kettle of fish.

"We generally use 3.5-4litres/ha of ipu, according to soil type, with 2litres/ha of trifluralin. We save a little by using the lower dose on the lighter land. Its only about 25 acres, but is easily picked out."

In specific fields where chickweed and speedwells are troublesome Panther (diflufenican + isoproturon) is added, again on recommendation, at 2litres/ha along with the same rate of trifluralin. "But we then cut the main ipu accordingly to 1.5-2litres/ha."

Wild oats and cleavers, the latter mostly on headlands, are generally tackled specifically in spring when any problems are more easily seen, he says. Sterile brome, confined mainly to an old ditch line, has been contained by hand pulling.

Volunteer barley in end Aug-sown oilseed rape merited a spray of 0.3litres/ha of Falcon (propaquizafop) with cypermethrin against flea beetle on Sep 18. A second hit on later volunteers may be needed. But apart from some patchy slug and pigeon-hit areas the crop should compete well with broad-leaved weeds, Mr Pettitt believes. &#42

BAROMETER ROUND-UP

&#8226 North: Despite having only two cereal fields ready for post-emergence spraying, Keith Snowball is relatively relaxed. There is virtually no blackgrass on the farm, despite its presence four miles away. "We are just about drilled up, but it certainly hasnt been in perfect conditions and some fields havent been rolled. We base our programme on Stomp, ipu and a bit of dff, upping the rates slightly where there are wild or cultivated oats. I like to roll first for better weed control." This year a 1ha (2.5acre) trial of Twinagros coded herbicide JV485 will be monitored. Soil condition is said to be much less critical than with ipu, he notes. "So if it goes onto a cloddy seed-bed it really doesnt matter."

&#8226 West: Warm weather has made Steven Mackintosh wary of treating cereals too soon with his standard ipu/dff mixtures, even though some have three tillers. The farm is blackgrass-free, main target being annual meadow grass. "It has been so mild I have been worried about crop damage. We have only done about 90ha out of 330, but I dont really feel behind. For the wheat and barley we use 1.5-1.75litres/ha of ipu with Grenadier to get the dff, sometimes with 0.5litres/ha of Duplosan to deal with large volunteer oilseed rape. We have looked at other products, but this usually works well. Our main change will be on the naked oats where we will substitute Lexus Class for pre-emergence Prebane which scorched the crop last year."

&#8226 South: Apart from one field with known blackgrass, Patrick Godwin is in no hurry to apply his ipu-based programmes. "We jumped on the wheat with blackgrass promptly with Dicurane at 4litres/ha." But with soils still warm he is reluctant to do much more to avoid losing ipu persistency. "It can deteriorate fairly quickly." Manganese and copper already applied with the first aphicide should help harden crops for treatment shortly, he hopes.

&#8226 South-west: With nearly all his cereals and oilseed rape receiving 2litres/ha of pre-emergence trifluralin, Stewart Hayllor is confident of controlling his most troublesome weeds, annual meadow grass and ryegrass. "It also does a fair job on pansies, chickweed and fat hen, and its cheaper this year. We will follow up with mecoprop, hbn or ipu at various rates. We are certainly no further behind than last year when weed control was very good. If I can match it I will be well pleased."

&#8226 Scotland: With fields under water in the worst floods for five years Eric Haggart is beginning to despair of applying any autumn cereal herbicides. A Tolkan/Bolero (ipu/dff + terbuthylazine) mix will be used if possible. Katamaran (metazachlor + quinmerac) on early drilled oilseed rape is working well, albeit slowly, he reports. But Sept-sown Panther is struggling in cold, wet soil and may not survive the winter.

&#8226 N Ireland: Aphids rather than herbicides are uppermost in Michael Kanes mind. Cold wet weather means crop and weed growth is slow, but aphicide is urgently needed to counter BYDV. Most weed-killing is normally post-emergence. "But we have done 40 acres of wheat pre-em with ipu and trifluralin just to get on." Flurtamone-containing Ingot will be used to deal with silky bent.