Farmers Weekly Interactive

North: Keep an eye on aphid levels

With June being largely dull and wet then plenty of sunshine is now required this month for grain filling. In winter and spring cereals aphids will need monitoring until the crop has reached the milky ripe stage. After this point yield responses to insecticides are seldom worthwhile.

The threshold is two thirds of tillers infested with aphids, and using insecticides that are kind to beneficial insects such as pirimicarb or tau-fluvalinate are good options. In peas, aphid numbers have increased steadily and often exceeded threshold levels.

Winter barley crops are beginning to lose their green colour and have more of a yellow cast. If the crops are to be desiccated with pre-harvest glyphosate then it should be when the grain is less than 30% moisture content, or when grains retain a thumbnail impression.

Oilseed rape desiccation timing could be tricky this year in fields that have various levels of lean. Diquat could be an option if home-saving seed or where crops have lodged severely and stems have broken to reduce the effectiveness of glyphosate translocation. Due to more un-even crops this year a higher proportion of them will need some form of desiccation.

Spring oilseed rape crops are well into flowering. The sclerotinia risk is high due to the continued wet weather, so a fungicide is being applied in most instances. Seed weevil numbers are often exceeding threshold, so an insecticide is being applied with the sclerotinia fungicide.

In potatoes, a nightmare potato planting season means crop growth stages are all over the place. Pre-emergence herbicides have worked extremely well, although keeping blight spray intervals tight has proven tricky in the past few weeks. Blight fungicides with more kick-back activity have been used where intervals have been stretched. Aphids are beginning to appear in crops and in these later planted crops it will be a case of applying an insecticide to a much smaller crop canopy than normal.

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