Slip shows how granules control damaging pests
Slip shows how granules control damaging pests
By Andrew Blake
A HICCUP when applying insecticide granules to sugar beet on a Norfolk farm has dramatically demonstrated their value in controlling damaging soil pests.
A slipped drive chain on the applicator Robert Perowne used to apply Temik (aldicarb) granules when drilling Stallion on Mar 20 has produced a striking zebra-crossing effect (see right).
In the dark areas on his newly acquired 14ha (35 acre) field at High House Farm, Docking plant growth in treated rows is normal. In the lighter untreated areas, Docking Disorder caused by nematodes is expected to knock yield hard.
However, even the untreated areas have since grown back quite well. "If it hadnt been for the good bits we might not have realised we had a problem.
"I should have been paying more attention," admits Mr Perowne. "But it is the first time the chain has come off." It meant that only nine of the 18 rows on his drill received granules, leaving alternate 18-row blocks of treated and untreated crop.
High House Farm is on light sandy soil next to where Docking Disorder, a relatively localised condition, was first identified about 40 years ago.
"We had it 20 years ago on one field and I havent grown sugar beet there since." Despite irrigation and extra nitrogen the affected crop yielded only 5-6t/ha, he recalls.
Although relatively expensive, Temik at 6kg/ha is his regular defence against nematodes and aphids. "I had considered not using it, but now I am very glad I did. Last year we averaged an adjusted 62t/ha. Id estimate we are looking at at least 5t/ha less in the untreated areas."
Agronomist Andrew Melton, of Swaffham-based Sands Agricultural Services, says some plants hit by nematodes have very few roots. "Those that do are fanging dramatically. If we get a drought that could be especially bad news."
Although the new field has not grown sugar beet recently, it has a history of vegetable growing which is likely to have encouraged a build of soil pests, he believes.
This years wet spring particularly favoured the free-living nematodes, says Brooms Barn entomologist Alan Dewar, who has inspected Mr Perownes crop. In severe cases, Docking Disorder can reduce output by up to 50%, he says.
"However, I dont think he will see anything like that. The untreated areas have caught up quite a bit. Temik-treated crops tend to do well early on but slow up as the moisture runs out. If it had been drier earlier the difference probably wouldnt have been seen."
The main lesson of the slip-up is that, wherever practical, untreated strips could usefully be left to check the effect and value of inputs – provided doing so does not risk aggravating a particular problem, suggests Dr Dewar. *