Farm Ireland

Friday 23 March 2018

Control weeds in maize and sugar beet

SOME livestock farmers have turned to maize to deliver a portion of their winter feed requirements, but others -- particularly in the traditional sugar beet growing areas -- continue to rely on sugar beet and fodder beet to feed stock over the winter.

The indications are that the area of maize grown in the country may be back slightly this year, at around 22,000ha, and more producers seem to be sowing under plastic.

Whatever the growing environment, controlling weeds in both maize and beet crops present their own unique challenges.

Maize crops are now emerging through plastic and growing well, while later-sown crops in the open are just emerging. Controlling weeds and making sure crops have the required trace elements are the next priorities for maize growers.

The main post-emergence product used by farmers with maize not under plastic is likely to be Calaris. A rate of 1-1.5 litres/ha should be sufficient. To get the best residual results, this should go on at the 2-4 leaf stage, which will give up to six weeks' residual control and allow the crops to cover in.

Make sure there is adequate manganese and zinc to meet crop requirements; if this needs to be addressed then now is the best time to apply. As with any weed control programme, the effectiveness of the spray programme needs to be monitored.

There are a few weeds that can cause problems, namely black nightshade, orache and fat hen. These sometimes create difficulties with a second, later flush of growth emerging. A herbicide such as Bromoxynil could be used at a rate of 1.5-2 litres/ha to control any re-emerging weeds two to three weeks after the first spray.


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Difficult weeds such as scotch thistle or volunteer potatoes will need to be treated with a specialist herbicide such as Titus or Fluroxypyr.

Dupont have a new post-emergence herbicide out this year called Accent. Its active ingredient is nicosulfuron and it claims to provide good control of grasses, wild oats and some other broadleaved weeds such as cleavers, redshank and brassicas. But it has little residual effect so it needs to be used in conjunction with Calaris or Callisto.

Weed control is the main priority in beet crops, which have generally enjoyed excellent conditions this year. A combination of herbicides and mechanical means are usually deployed, depending on what suits individual circumstances and the machinery available.

Keeping weeds in check early on is critical to the overall performance of the crop.

A very popular T1 for weed control is Debut (30g/ha) plus Betanal Expert (0.5 litres/ha) plus Goltix (0.5kg/ha) plus methylated rapeoil -- Fortune or Diamond Toil. This is a good all round T1, but it may be poorer on mayweed, fool's parsley and bindweed. If so, replace the Goltix with 0.5 litres/ha of Venzar.

Goalpost, Wizard, Expert and Goltix are the main herbicides favoured by farmers for the T2 on beet. Goltix provides good residual persistence for weed control throughout the season.

Goalpost (3.0 litres/ha) or Betanal Expert (1.5 litres/ha) plus Goltix, Beetrix 1.5kg/ha plus oil is a good follow-on to the T1 where no charlock is present. Target weeds are fat hen, orache and marigold.

The T1 and T2 sprays should be up to 14 days apart to give best results. If midday temperatures continue to remain high then be careful not to scorch the crops.

Irish Independent