Farm Ireland

Thursday 26 April 2018

Numerous advantages to pre-harvest glyphosate


PJ Phelan

PJ Phelan

With a good forecast for this week, most farmers chose to sit tight on harvesting winter barley last week in Tipperary. Yields were in a range of 7-10t/ha with bushels of 67-69 and moistures generally high at 20-22pc.

Pre-harvest glyphosate was still being applied last week to some of the later crops which had received either late bagged nitrogen or liquid nitrogen.

Merchants are very reluctant to indicate a harvest price for green grain but I expect that it should make €160 at 20pc moisture content. There will probably be very little difference between the price for barley and that for wheat. Some wheat was harvested on Friday last for whole crop. The grain was at approximately 35pc moisture content and sold at €135/t.

Pre-harvest glyphosate application to cereal crops will give the most effective control of perennial weeds and thistle at a very cost-effective price. It makes for ease of harvesting, lower grain moistures and cheaper weed control in next season's crops. There are numerous formulations of glyphosate on the market with some claiming significant advantages over others.

Regardless of claims, it is important to ensure that timing of application is correct. The key is to ensure the grain is below 30pc moisture. This may be assessed with the thumbnail test. Press the grain firmly with your nail and if the grain holds the imprint the crop is fit for spraying.

Rates of glyphosate will vary depending on weed type, the concentration of the product and the formulation. If the application is to control annual grasses, late tillers and green growth on tramlines, 360g of active ingredient per hectare is adequate. For annual broad-leaved weeds increase the rate to 540g/ha and for scutch apply 720-1440g/ha. When using lower rates, the addition of an additive such as Arma is important with some formulations, so check the label.

Potato crops are generally looking well and blight control has not been difficult so far. Spraying intervals should not exceed 10 days and should be reduced to seven days if disease pressure increases. Change to fungicides containing more curative activity if blight is found in crops. Rotation of fungicide groupings is important to reduce risk of resistance and to comply with approvals under Pesticide Control Service (PCS). Magnesium deficiency is evident in some crops by the pale colour of foliage and yellowing between the veins. If this is the case, magnesium should be included with the next blight spray. Sulphur is a problem in some crops, particularly where low levels of sulphur fertiliser were applied. This may now be rectified with foliar applications.

Fodder beet is an expensive crop to produce and should receive a fungicide in late July/early August so as to prevent rust, ramularia and mildew. Approved products include Punch C, Lyric, Score and Corbel. Significant yield responses of 2-5t/ha have been obtained nearly every year, together with an increase in sugar content. Improved tops will also help to reduce harvest losses with belt type harvesters and will also give better tops for grazing.

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Maize continues to battle on despite very difficult conditions. Crops that were sown under plastic, while still backward, have reasonably good potential. The risk from eyespot on land in continuous maize production has been a problem on the south coast in recent years. This may be even worse this year due to the wet weather in July. Fungicides which may be used off label include Punch C, Sanction, Lyric and Modem. Add magnesium and zinc if soil levels are low.

Many of the poorer crops would have been ploughed out but for the fact that residual herbicides had been applied and would have damaged or destroyed any subsequent crop sown this year. The more backward crops may benefit from the application of foliar feeds but the economics of spending any more money on these crops is questionable.

Patrick J Phelan is a member of ITCA and can be contacted at

Indo Farming