Syngenta’s insecticide seed treatment thiamethoxam, which is being developed for peas, can give a dramatic reduction in seedling pests, PGRO trials have found.

Crops treated with the insecticide, which is used widely in oilseed rape and sugar beet, showed an 80% reduction in thrips and a 70-85% decrease in pea and bean weevil numbers in some cases.

“For the first time this year, we have been comparing TMX with conventionally applied insecticide sprays,” said PGRO technical director Anthony Biddle.

“For weevil, the best we got was about 30% control with a Hallmark spray applied early. But with thiamethoxam we got 85% reduction – it was dramatic.”

Adult weevils feed on the leaves, causing characteristic U-shaped notches, explained Dr Biddle.

They then lay eggs which get washed into the soil and the larvae hatch out and feed on the root nodules.

However, with thiamethoxam (TMX), Dr Biddle noticed a big difference in root structure. “You have virtually got no nodules where the weevils have been feeding and almost a full complement of nodulation where a seed treatment has been used,” he said.

An added benefit from TMX was the good control of aphids which transmit the pea enation mosaic virus that can lead to yield and quality loss.

Dr Biddle said crops treated with the insecticide also produced higher yields. Yield increases of 45% in vining peas and 25-30% in combining peas had been recorded, he pointed out.

Dr Biddle said thiamethoxam was a “complete seed protectant” from pea pests and its approval could not come soon enough.

The delay was due to problems concerning seed treatment doses as varieties of pulses come in different seed sizes, he added.

Syngenta is seeking approval for it to be used on peas in the UK in time for next season. It has already been approved in the USA, Belgium and the Czech Republic.

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