Nozzle choice key to blight control
By Charles Abel
NOZZLE choice can double blight fungicide coverage of potato plants during early growth and boost the amount deposited on lower and middle leaves by 50% once the haulm closes.
Those are the findings of Novartis applications specialist Tom Robinson. When potatoes are sprayed with conventional fan jets early in the season, a lot of spray is wasted to the ground, he warns.
By contrast, the use of cone nozzles and angled sprays puts some horizontal movement into the spray, and can easily double the amount of spray collected by the crop at this early timing.
"Of the angled fan nozzles, Delevan Tilt jets, Lurmark Twin Caps or Teejet Twin jets work well. Hollow cones also do a good job but create more drift. Preferred nozzle ranking order would be angled fans, followed by hollow cones, followed by conventional fan jets at high pressure."
By the third spray in a blight control programme, the canopy will have closed over and the challenge is to get spray droplets to penetrate down to the middle and lower parts of the crop, says Mr Robinson.
Upper foliage effectively shields lower leaves from the spray, leaving parts of the haulm unsprayed if protectant-only materials are used. "Here, we have found moving from a standard fan jet to a hollow cone or an angled spray increased spray deposition on both lower and middle leaves by 50%.
"Again, droplets need to move horizontally to penetrate the canopy. So the jets used at the earlier timing remain equally valid.
"Coarse droplets falling vertically hardly get beyond the canopy surface," he says. For this reason, air induction and low drift nozzles should not be used. Finer drop-lets can ride in horizontally on air turbulence.
"In our trial plots, simply moving from a standard fan jet to a tilt jet reduced blight infection by about 30%." *
Blight fungicide Fubol has received a new lease of life in time for the spud spraying season. Like many other fungicides metalaxyl, the systemic part of Fubol, used to be included in two forms. "However, only one form actually controlled blight," says Novartis field crops manager Michael Tait.
New manufacturing technology means Fubol Gold (metalaxyl-M + mancozeb) now contains the functional form of the active only. "A lower amount of chemical is released into the environment, yet its systemic performance against blight remains equally strong."
Laboratory tests suggest metalaxyl-M has significant systemic activity, showing better movement to leaves both above and below the one treated than with propamocarb.
"For maximum protection, Fubol Gold sprays should start just before plants start to meet along the rows," says Mr Tait. If blight risk is high spraying should start immediately, irrespective of crop growth stage.
Fubol Gold is available in 0.95kg packs, enough to treat 0.5ha (1.24 acres).
Grain fund finds favour
By Andrew Swallow
USING a grain-fund to market grain buys management time, provides a benchmark for open market sales, and keeps the bank manager at bay, says one enthusiastic Beds grower.
From an expected 1650t wheat crop at D & M Farms, Michael Dunn has committed nearly half to Cargills Short-Fund. It is a decision he took last August, before drilling, and it is the third year running he has locked into the scheme. He has not been disappointed yet.
"Year on year, our open market sales seem to end up a £ or two behind the fund, even after commission," he says.
That is charged at 5% of the feed price achieved. "So we do not pay commission on any premium paid." As a third of his commitment is milling variety Soissons, it is a useful bonus.
"Last year we made a £16/t premium. We could have taken an £18/t market, but that had no fall-back so we took the safer home."
This harvest he expects to have a total of 650t of Soissons, and about 1000t of biscuit wheats.
Mr Dunn has the option of fixing the fund price at any time. Last years deal climbed to nearly £80/t at one point, but he did not lock in and the value slipped, closing at £78.76, or £74.82 after commission. Payment is guaranteed by Jan 15, with movement at any time up to Dec 31 under the short fund terms.
"But Cargill are very good and will work with you as far as possible on movement," he says. Empty stores are cleaned down and used to earn extra cash through third-party storage for the rest of the year.
Monthly statements keep Mr Dunn informed of the funds progress. At the end of April it had reached £79.50 for the 99 crop. "It opened at £70/t in August, so it has done quite well so far."
But he is reluctant to lock in at that level, even though it is above his budget figure of £72/t of feed in November. "I think it is going to keep going and we will see the magic £80/t again," he says.
Mr Dunn reckons to be on the phone to Cargill trader John Tanner, or an alternative merchant, about twice a week. Markets are discussed, and the fund performance checked against other merchants deals. "And a neighbour uses a similar Dalgety scheme, they seem to come out neck and neck," he notes.
Committing all his output to funds or pools, including 170t of oilseed rape, is dismissed by Mr Dunn. "I feel we would lose touch with the markets and give up."
So far ACCS membership has not been necessary. But that could change for harvest 2000. "We have done all the modifications and records required, so could jump in at any point." *