PAY CLOSE attention to temperatures before applying plant growth regulators in order to achieve optimum crop uptake, Syngenta has told growers.

This follows research that found significant differences in the rate of PGR uptake into winter wheat during colder weather, said the firm‘s Alison Bosher.

The research compared Moddus (trinexapac-ethyl) and chlormequat uptake when applied at 7o C. Almost 60 hours were needed to achieve 70% uptake of chlormequat, compared to 20 hours for Moddus, the results showed.

“While 7oC may not sound unusually cold, 30 years of weather data shows the average temperature in April – the key month for PGRs – is just 7.9o C.

“So it‘s important to take temperatures at time of application into account,” she said.

Where crops are forward and have a large number of tillers, weak stems present the greatest lodging risk, she explained. In such cases she suggests an application of Moddus + chlormequat at GS 31-32.

In more backward crops, poorly developed roots are a greater threat and the above treatment should be preceded by an earlier application of Moddus at GS 29-30 to strengthen roots, she said.