Words by Bill Cabout, Ruralco Chemical Manager
Autumn Sown Crops
Most autumn sown crops have already been planted by now. Seed treatment only persists for a certain amount of time after planting, until the start of tillering (GS21). Those crops which were drilled before mid-April will no longer be protected from aphids. Aphids can carry the disease Barley Yellow Dwarf Virus (BYDV), which will severely damage yield if your crop gets it at this early stage. It is a good idea to apply an approved insecticide even if the numbers of aphids are low, as this often proves to be good insurance. Whether a follow-up spray is required three weeks later will depend on aphid numbers. Weather conditions will play a key role, with cold and wet conditions typically resulting in lower aphid numbers. A good way to check up on aphid numbers is to look at the Lincoln Suction Trap data on the FAR website.
This year there are large numbers of grass grub about, and this can decimate a crop before you even realise. Diazinon granules at drilling will provide up to 5 weeks protection from grass grub, so this protection will now also be wearing off. Check your crops and if grass grubs close to the soil surface are found, your crop may need spraying with liquid Diazinon to control these. This is ideally put on during rain, so it is washed into the soil where the grubs are.
Slugs have been an ongoing issue in some crops throughout the autumn. Monitor your crops closely and if need be, apply more slug bait.
If you have some early weed strike not controlled by your pre-emergent spray, it is best to clean this up while the weeds are small. Which product to use is determined by which weeds are present. Talk to your Ruralco Representative for the best options.
For the control of Brome grass, we can use Rexade (Pyroxsulam + Arylex). This combination controls wild oats, rye grasses and brome grass as well as many significant broadleaf weeds such as fumitory, chickweed, cleavers, field pansy, speedwell, shepherds’ purse, white clover, and volunteer linseed. It is for wheat and triticale only and can be applied from GS13 to GS31. If you are applying to control brome it can be applied twice, otherwise apply once only. It is available in a 2kg pack, and the rate used is 100g/ha plus 250ml non-ionic surfactant /100lt water. Please check the withholding periods for planting following crops as it is up to 12 months currently on some crops. This product is for wheat and triticale only. This year we have also have a generic Pyroxsulam (Merito) available which we can use instead of Rexade, at a rate of 500ml/ha.
If you are planting wheat and barley during the winter month’s you can use Firebird or Invado pre-emergent up to the 30th of July. After this date, it doesn’t work as effectively as the weeds are growing too quickly.
This season we have a new pre-emergence herbicide for wheat and barley from Adama called Tower. It contains a new active ingredient for the New Zealand market called Chlortoluron, it also contains Pendimetalin and Difluenican. It controls a wide range of broadleaf weeds and selected grass weeds and is suitable for use in both autumn sown and spring sown crops. The rate used is 2.5lt/ha. Please contact your Ruralco Representative for further information.
Barley: Firebird or Invado can be used as above to control weeds pre-emergent.
Clover: After drilling Armada/Preside gives good control of certain weeds without concern about clover size. Propyzamide (Kerb) can be applied to white clover seed crops during the winter months from June to Aug for the control of grass weeds and some broadleaf weeds. Weeds not controlled by Propyzamide can be controlled by various products depending on weed spectrum during July and August. Contact your Ruralco Representative for options.
Ryegrass: Most Grass seed crops have been sown by now. With the good growing conditions this year an early post emergence spray could be worth looking at to control any weeds that have appeared before winter. What to use will depend on your weed spectrum.
Barley Grass Control
For the control of barley grass in pastures, apply ethofumesate (various products are available) at 4 L/ha. Timing is important for effective control. Application should be after the main germination has occurred following autumn rains. Ethofumesate provides residual activity for about 8-10 weeks, therefore timing is essential to ensure that the residual activity is effective during the period of spring germination of the weed. Ideally, apply during the last week of June or the first week of July to achieve the best results.
Weed Control in Lucerne
The ideal time to control weeds in Lucerne is during the winter dormancy period before the onset of spring growth, so there is no crop damage or suppression. Paraquat is the ideal broad-spectrum weed control for Lucerne, as it provides excellent control of annual and many perennial broadleaf weeds, as well as most grass weeds. Paraquat can be mixed with a residual herbicide, such as atrazine, to provide season long weed control. Atrazine should not be applied to stands less than 12 months old. Terbuthylanzine (Asset) can also be used but can only be used on stands older than 24 months. Stands 6- 12 months old can only be sprayed with paraquat. Any weeds not controlled by this can be looked at again in the spring.
A new product Chateau has been released for weed control in Lucerne. This can be used on stands over 12 months old and needs to be applied to bare soil to get the best results, so paraquat will need to be applied with it. If the stand has a lot of leaf, you may need to spray paraquat first and then come back with Chateau a couple of weeks later to get the best out of it. See your Ruralco Representative for your best option.
Monitoring Stored Grain
Monitoring grain during storage is a valuable tool in maintaining quality. This becomes more important the longer the grain remains in storage because deterioration in seed quality early in storage is slower and insects are sparse and not easily noticed. Temperature and seed moisture content are important indicators of grain quality that influence insect and mould activity. Once grain is in storage, monitoring for insects and mould once a month will give early notice of any problems occurring and action can then be taken to control these problems.
With all the above scenarios talk to your Ruralco Representative for the best options for you and your situation.