Datural, Mexican marigold, and amaranthus are common weeds in maize farms. If not controlled, they can lead to a yield loss of up to 30%. Understanding how the various maize herbicides in the market work will help the farmer minimise losses.
Stellar Star
Stellar Star is very strong on Gallant Soldier, Datura and Mexican Marigold but slightly weak on some populations of Amaranthus. Setaria and Lovegrass are controlled up to the 2-3 leaf stage, and Eragrostis is taken out right up to the end of tillering.
Unfortunately, Brome and Sudan Grasses are poorly controlled, so a strong pre-emergence herbicide must be used from the outset. It tends to have limited residual control, so be aware of applying at the 3-4 leaf stage and being caught out with later germinating weeds.
Lumax
For several years, Lumax herbicide has been the established benchmark for maize weed control. It is very strong on a wide spectrum of weeds but can struggle on large Amaranthus and Gallant Soldier. It is also the strongest option on grass weeds, which must still be small, but it controls Brome, Ryegrass, Napier Grass, and Setaria.
Be aware that some varieties are sensitive to S-metolachlor applied post-emergence; this is not always obvious until you see the product applied to a variety trial, where some damaged plots stand out.
Also, bear in mind that mesotrione has a 9-month plant-back period on some legume crops, so be careful if you plan to plant beans in the off-season.
The Governor herbicide is a recent generic alternative to Lumax, but it uses acetochlor instead of metolachlor. This makes it slightly safer on the crop but slightly weaker on established grasses. If you have very fertile soil at high altitudes and Lamb’s Quarter (sometimes known as Fat Hen) is a problem, this is actually better than Lumax.
Surestart
An excellent new herbicide from Corteva, Clopyralid has some modes of action that are new to the crop in Kenya. It is excellent on Thistles, Mexican Marigold, and Gallant Soldier, but be careful of planting legumes or potatoes in the off-season—the official plant-back period is 18 months! The upside of this is that Surestart is THE product to use where Crotalaria or volunteer potatoes are a problem. Apply only up to the 3-leaf stage.
Monolith
Now approved by Greenlife Crop Protection, this product needs to be carefully understood. Containing the Sulphonyl-urea nicosulfuron, this is excellent on grasses and will control Brome better than clethodim!
Beware that some varietals are sensitized to nicosulfuron, so DO NOT apply it without first consulting your seed supplier to determine whether it is safe for your crop.
The plant-back restriction to follow with wheat or barley is only 4 months, which is extremely useful. However, Monolith contains mesotrione, so be careful of planting a legume in the off-season.
And, in the rare situation where you are at a high enough altitude for Cleavers to be a problem weed in your maize, this is the only approved product containing fluroxypyr!
Auxo
Auxo has a useful range of weed activity, including Gallant Soldier and Blackjack. However, the reliance on bromoxynil means there are several resistant populations of Amaranthus.
Bromoxynil can also scorch the crop in bright, hot conditions, so caution is required. Control is best when weeds are small, particularly on Eleusine and Digitaria / Crab Finger grasses.
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2, 4-D
2, 4-D herbicide is strong on most broadleaved weeds, except Cleavers, but no activity on grasses. It also needs to be applied at the correct growth stage to avoid the risk of crop injury.
Servian
Servian herbicide is a specialist product for Water grass control. It can be mixed with other herbicides where approved, but remember the 3-month plant-back restriction on pulses and 13 months on Sunflowers.
Buctril / Badge / Breakdown
Buctril, Badge, and Breakdown herbicides are rarely used but approved for application to maize. They provide very good all-around broadleaved weed control but avoid applying them in hot and bright conditions. Strengths include brassicas, Gallant Soldier, and Datura, but they have no grass activity and can struggle on Amaranthus.
Source: Cropnuts
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