Managing slug control in late-drilled wheats Wetter conditions and slower crop growth make good slug control crucial with later-drilled wheats; especially where they follow oilseed rape. But pelleting should be very much the last resort, believes a technical adviser. Although periodic cultivation can be very useful and mid-late October drilling gives more time for it, Agrii regional technical adviser Tim Horton (right), does not advise this approach either. Not least to avoid compromising the key purpose of delayed drilling in the first place – black-grass control. “A split-field slug monitoring study we ran several years ago clearly underlined the value of an extra cultivation in killing eggs and exposing adults to predation,” noted Mr Horton. “However, our Stow Longa black-grass technology centre work shows the best approach with late-drilled wheat is to cultivate early then move as little soil as possible ahead of, and at drilling. “In my experience it’s perfectly possible to reconcile these two apparently conflicting approaches with minimal reliance on pelleting. The twin keys to success here are effective trash and drilling management. Get these right and you’ve done a good 80 per cent of the slug control job.”
Surface trash Concentrations of surface trash simply have to be avoided, Mr Horton has no doubt. As well as maintaining the moist environment they need, rows of trash protect slugs and their eggs from predation by birds. So good straw, chaff and (with OSR) pod trash chopping and spreading is an essential first step.
Alongside this, he stresses the importance of early cultivation to both bury the trash and bring slug eggs to the surface to desiccate. “The depth of cultivation will depend on your soil type and condition,” he said. “The priority is to set up the ground to weather so you can create a seedbed from mid-October with the least extra soil movement, keeping as much black-grass as you can soundly asleep. “You may need an extra cultivation to achieve the trash incorporation you want and openup the clods that shelter eggs and adult slugs in heavy land. But if it’s necessary, do it early and at an angle to the first cultivation, then use no more metal until you drill.” While monitoring with nontoxic baits ahead of drilling can be beneficial in assessing slug risk, Mr Horton generally finds it unnecessary as, in most cases, the level of threat is highly predictable from the wetness of the soil, the amount of trash and the quality of the seedbed. “Monitoring can give you a false sense of security if conditions are on the dry side,” he pointed out. “Also, I like to avoid feeding pests wherever I can!”
Seedbed quality Alongside the most effective trash management, Mr Horton stresses that what you drill, the way you drill it and, most importantly, the
Tim Horton examines post-harvest oilseed rape trash.
quality of your drilled seedbed are all especially critical in late-drilled wheat slug control. “Two things matter above all else in this respect,” he insisted. “Limiting slug activity on the one hand, and boosting crop establishment on the other. “Firm, fine seedbeds do both. They seriously restrict slug movement to minimise both seed hollowing and surface grazing. And they maximise seed-to-soil contact and moisture retention so the crop grows away from the slug challenge as rapidly as possible. “Achieving them can be difficult at this time of the year, however. So you need to stay off the land until you can drill at an even 3–4cm into a seedbed without clods. With such a narrow weather window, it’s tempting to cut corners. But it really isn’t worth the risk. If conditions aren’t in your favour it’s best to hold
off and drill in the spring. “As conditions usually only make it possible to roll once after drilling, it’s vital to get this right too. Essentially this means rolling within two days of drilling and not too fast. Remember, the degree of consolidation you get depends on the time the roller is actually pressing down on the soil as much as its weight.” Mr Horton also recommends using good quality seed that has been vigour as well as germinationtested, treating it with Deter to reduce seed-hollowing and a manganese or nutritional dressing to encourage rooting, and providing sufficient available phosphate in the seedbed.
A last resort While he accepts that slug pelleting may be needed in many cases, he continued over...
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14 www.farmersguide.co.uk September 2017
1-25 ROP Sep.indd 14
Published on Aug 31, 2017