A two-stage approach to weed control is essential to maximising maize yields according to ProCam agronomist Justin Smith, who explains that a pre-emergence application of pendimethalin followed by a two or three-way combination of post-emergence active ingredients can make the difference between acceptable and exemplary crop performance.

“As recently as less than a decade ago, growing maize in the UK was almost perceived as a much less technically involved process,” Justin describes. “Many crops received little in the way of agronomic care beyond a decent amount of farm muck and a basic application of a post-emergence herbicide, after which the crop would be left to its own devices until harvest.

“However, as inputs including seed, diesel and labour have increased in price, and the value of home-grown forage has risen, maize crops must now produce a much greater yield to cover return on investment.

“As a result, most maize is now grown with a professional level of detail, with close attention being given to the creation of a fine, firm, but not overly compacted seedbed and a greater focus on nutrition including the use of starter fertilisers.  Professional maize growers also have a better appreciation of the value of applying a range of herbicides at both the pre- and post-emergence timings.

“But, in a year when there’s a lot of talk about reducing inputs to offset the effects of recent weather patterns and suppressed farm incomes, there’s a danger this year’s crops might be subjected to corner cutting. That, in my opinion, is a precarious strategy, especially as maize is such a fickle crop when it’s in its infancy, with a decent amount of TLC needed to ensure crops go on to produce a high yielding and reliable source of roughage, dry matter and energy.”

Justin explains that a frequently used cost-cutting tactic is to exclude early season weed control. “Omitting the pre-emergence herbicide spray can be an easy decision to make, with growers often reticent to spend any additional money until the crop has fully emerged. But a recent ProCam trial indicates that a residual herbicide application is vital to helping to achieve a sustainable, high-yielding crop.”

According to Justin, a pre-emergence application of Anthem (400g/l pendimethalin) is a reliable and cost-effective insurance policy in the fight against a wide range of grasses and broad-leaved weeds. He rationalises this by explaining that the 2025 trial showed that even during the year’s dry spring, pendimethalin delivered good levels of efficacy.

“Using pendimethalin at the pre-emergence timing won’t give 100% control of every weed or species, but it does buy a bit of time and crop security by holding back weeds, so they don’t out-compete the vulnerable young crop,” Justin continues. “And, with the threat of early season weeds reduced, there’ll hopefully be less need to rely on a large chemical stack at the post-emergence timing which could put undue pressure on the crop at a vital time in its development. There’ll also be less for growers to worry about should the weather take a turn for the worse or if the spray contractor is unexpectedly delayed as the crop will already have received some protection.”

In terms of post-emergence weed control, Justin recommends using a product with two or three active ingredients to mop up any weeds not controlled by the pre-emergence treatment. “Spandis (40 g/kg prosulfuron, 400 g/kg dicamba and 100 g/l nicosulfuron) or Dragster (148.15 g/k rimsulfuron and 92.5 g/kg thifensulfuron-methyl) are good options as their inclusion of multiple active ingredients provides better control of grasses and broad-leaved weeds and also reduces the risk of resistance building against any individual chemistry.”

Justin also advocates the use of partner products at both herbicide timings: “An adjuvant such as Velomax will enhance the performance of residual chemistry by improving the distribution of the herbicide on the soil surface. It also helps to hold the residual product in the ‘active zone’ for longer during periods of drought or heavy rainfall, ensuring better herbicide efficacy and reducing the risk of crop phytotoxicity.”

To improve the efficacy of post-emergence treatments, Justin recommends the inclusion of a nutrient growth promoter and biostimulant such as Hadron which delivers foliar-applied nitrogen and zinc to the crop to enhance root development, improve nutrient uptake and help the crop grow away from any checking that the herbicide might impart.

“Hadron proved very effective during last year’s drought, enabling crops to tolerate the dry conditions more efficiently. It’s another cost-effective way of insuring the crop’s performance against environmental stresses, and another tool that growers can use to ensure their forage clamps are adequately stocked.”