We are having to keep a close eye for disease symptoms in soya bean crops due to the heavy rains in the past few months. Last year we received 1930mm, almost twice the annual average of 1,000mm, which could see yields fall by up to 25% because of disease.

Extensive rainfall generally favoured the development of soya bean crops, but it also favours the spread of pests that damage soya bean plants. After the heavy rains that began last August (through the climate phenomenon El Niño), Argentina reduced its soya forecast due to a combination of delayed planting and loss of hectares by flooding.

In Bigand, soya bean planting was delayed 15 days beyond the optimum date. I started my planting on 1 November, and around 1 to 1.5% of land (5-10ha) was lost by flooding.

The crop is at the “flowering – start of pod formation” stage and I am deciding which disease treatments to deploy.

The risk of disease spread has eased a little in the last month though, as there hasn’t been any significant rains since 20 December. In addition, I opted for varieties that are resistant to Cercospora sojina (Frogeye Leaf Spot) plus I went for wider row spacings of 52.5cm to help reduce spread.

At first it is very difficult to predict what the damage from diseases will be by the end of the cropping cycle – last year where there was virtually no damage.

The most important diseases are frogeye leaf spot and septoria leaf blotch. Soybean rust can cause losses. Therefore, I am closely monitoring my plots for disease and expect to eventually go in with a fungicide mix, such as epoxiconazole and a strobilurin.

Federico Rolle farms 2,250ha of rented arable land in the Pampa area of Argentina. He grows soya beans, sorghum, maize and wheat using no-till techniques and GM crops. He has a part-time role helping Brown & Co in the region.

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