By David Jones, Broad Acre Agronomist, Msc. Agriculture
With many wheat and barley crops being dry planted this season, broadleaved weed control is likely to be a challenge when the rain does arrive. We review the options available and the spectrum of weeds they control, how to get the best out of them and how to avoid problems with following crops.
Good all-round herbicide that is useful on larger weeds. Cut off Growth Stage 32, good on Cleavers in warm conditions but poor control if nights are cool so the addition of Derby or Lancelot is sensible if Cleavers are likely to be present. Low rate of clopyralid adds Thistle activity but if planting pulses straight behind exercise caution.
Buctril (MCPA + bromoxynil)
Strong on volunteer canola and brassicas such as Wild Radish. Slightly weaker on Amaranthus, especially if the farm has used bromoxynil frequently in the past. Gaps include Cleavers and Thistles, but these gaps can be filled with Derby for the former and Lancelot for the latter. No following crop restrictions is very useful when double cropping. Cut off timing is GS32.
Reasonable spectrum of weeds, no following crop issues and some useful variation in modes of action. Carfentrazone can scorch badly in bright conditions however, and tank mixes with epoxiconazole should be avoided. Good activity on Cleavers, Fat Hen, Brassicas, Mexican Marigold and Bindweed, but weak against some Amaranthus, Commelina and Mallow.
Very good on Gallant Soldier and small Cleavers, especially in cool conditions. Good on Brassicas but note that Clearfield Canola volunteers will not be controlled. Larger cleavers will struggle even at 70mls/ha rate, but strong on Mallow and few following crop restrictions due to limited residual activity. Good on Adamsonia, but it is essential to wash the sprayer out with an approved tank cleaner before going into non-cereal crops.
Lancelot (aminopyralid + florasulam)
Good on small cleavers but as with Derby, will not control Clearfield Canola volunteers. Straw from aminopyralid-treated crops should not be baled and used for animal feed or bedding, as residues in the manure are highly active on potatoes and pulse crops. Strong on Thistles, Bindweed Amaranthus and Strumarium, but exercise caution if Legumes or Potatoes are likely to be planted after the cereal. Clean the sprayer thoroughly with a tank cleaning product to avoid damage to pulses and canola.
Huskie (bromoxynil + pyrasulfatole)
A very useful mix against Gallant Soldier, Cleavers and excellent activity on young Mallow. However Amaranthus control tends to be variable and without a hormone partner it struggles on larger Chinese Lantern and Fat Hen.
Tribenuron is a very useful tank mix partner but hold little value in its own right. No activity on Cleavers, Mallow, Commelina, Gallant Solider and most Amaranthus populations (due to ALS resistance), but a useful late clean-up in cereals for Fathen, Shepherd’s Purse and Brassicas. Supresses late Bindweed and few following crop restrictions.
Sekator (amidosulfuron + iodosulfuron)
Normally considered a Brome herbicide with some broadleaved weed activity, Sekator is actually a very useful herbicide against Cleavers and Brassicas. Active at very low temperatures (useful when targeting Cleavers during periods of cold nights) and also strong on Bindweed, Commelina and Fat Hen.
More of a pulse herbicide but useful activity on Watergrass, and helps supress Brassicas and Cleavers when applied to young plants. Requires warm conditions and above all, good spray coverage so nozzle choice is crucial. Useful Bindweed activity, and when mixing with Lancelot could be a good late-season clean-up approach for fields that have escaped earlier herbicides.
A very strong broadleaved herbicide whose only real weakness is Cleavers and only moderate activity on Mallow seedlings. Safest to apply when the plant is tillering up to GS32 – later application can cause serious damage and head trapping as the ears emerge. Always clean the sprayer well as residues stick on the sides of plastic tanks for several spray cycles.
Checklist for successful weed control
- Know your weed species
- Rotate different modes of action (crop rotation is the best for allowing diversity of chemistry)
- Grow strong, competitive crops
- Apply herbicides to small, actively growing weeds
- Use clean water in the sprayer
- Follow the herbicide label and use water conditioners and appropriate adjuvants.
- Apply accurately, with a well maintained sprayer and the correct nozzles.
- Clean the sprayer out thoroughly after use in accordance with the label.
Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the future of how we feed the planet.
Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health.
The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts).
Till next time,
David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.