Farm Ireland

Wednesday 22 November 2017

How to control weeds and save some money

Cotyledon weed
Cotyledon weed

Michael Hennessy

Over the years I have always emphasised the importance of timing to achieve good control. If you get the timing correct it can mask poor herbicide choice, give excellent weed control, reduce any side effects on the crop and improve yield. However, it will not kill weeds that the selected herbicide cannot control. Therefore knowing your weeds is critical. This is where records come into their own.

In beet, the weed control options are limited, therefore timing becomes hugely important and beet growers would not dream of trying to control weeds 5-6 inches tall as control will be poor. The same general principal should be implemented in spring cereals. In spring cereals the target weed size for weed control is the one to two true leaf stage of the weed (see picture). At this stage weeds are most sensitive and easiest to kill. A low rate of herbicide will control most weeds (there are a few exceptions) and you do not have to worry about other weeds that have not emerged as a competitive crop will control them.

Weed control options

There is a wide range of products available with many new herbicide products on the market this year. Most of these products are parallel imports using a similar label as existing herbicides on the market. Herbicide have different strengths and weaknesses, so choice is affected by the weed type in the field, size of weed, growing conditions and size of crop canopy.

Where weed control has been poor in the past, consult your agronomist as timing restrictions on herbicides and identification of poorly controlled weeds (in the past) is essential to order to select which herbicide to use in 2015.

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