The PGRO issues advice on desiccation for peas and field beans

"Where possible, pea crops should be direct combined without desiccation as this adds to production costs and there will be an amount of crop loss," advises Becky Ward, PGRO senior technical officer. "However, crops with excessive amounts of green weed growth still present, and where die back is not uniform, will benefit from the application of a desiccant. The application will even up maturity and allow combining to take place earlier."

"It is important to carry out the application at the correct crop growth stage. With peas this is when the moisture content is between 40-45% and the crop is turning yellow; the bottom pods are parchment-like and the seed within is hard; pods in the middle of the plant are becoming parchment-like, the seed is rubbery and can be squeezed between finger and thumb without splitting; top pods are fleshy, still green/yellow, and the seed splits if squeezed. Desiccation of peas much before the stage outlined here can encourage lodging. Increased shelling out can also be an issue if, after desiccation, harvest is delayed."

For field beans, Ms Ward advises that desiccation has little effect on the green stems but, again, can be useful if weeds or an uneven crop are a problem. "Timing is vital to maximise yield potential and seed quality. Growers should spray when 90% 0f the pods are dry and black and most seed is dry (GS 309)."

The most widely used desiccant is diquat. After application harvesting can take place 4-7 days later. There are glyphosate and glufosinate ammonium formulations which can be used, but these products tend to be slower-acting and crops are generally ready to harvest 10-14 days later. Do not use these latter two materials on crops destined for seed.