• Chocolate spot already now widespread in field bean crops
• Repeated rain showers risk splash spread of spores onto new leaves
• Protection of emerging new growth in mild conditions is the priority for growers
• AMISTAR shown in field trials to have good results in protecting leaves from infection

Field bean crops have come under severe disease pressure through the prolonged period of extremely wet weather. Every rain event risks further spreading chocolate spot spores onto new growth, warns Syngenta Field Technical Manager, Simon Jackson.

Latest reports from the PGRO have highlighted the high incidence of chocolate spot (Botrytis fabae) and the ongoing need for urgent action. Early applications of fungicide may be needed to prevent further development, it advises.

Growers and agronomists are urged to check crops as a priority, especially on the underside of leaves where leaf spots may be more prevalent. PGRO warns the effects of failing to control early chocolate spot infections can be devastating.

Simon Jackson advocates protecting emerging new leaves from continuing infection at the earliest opportunity. Field trials and growers’ experience have shown AMISTAR can keep leaves green and clean of infection, until weather conditions dry up and the main fungicide programme kicks in.

“It provides good protection of clean leaves, but for added curative activity in high pressure situations, on infected crops in continuous wet weather, tank-mixing a product with some curative activity, such as metconazole, would further increase results,” he suggests.

With recent research into bean disease resistance management in mind, growers should opt to avoid the use of an SDHI at this stage in the season, where the advanced technology is to be utilised later in the programme.

One of the challenges with wet soils is finding a spray opportunity and a period where crops are not under stress for application, highlights Simon. Growers should also be alert for potential risk of frost damage exacerbating any spray effects, ideally applying before any frost forecast, or leaving at least five days after a frost event for plants to recover.

“The impacts of early chocolate spot under such high-pressure conditions can be severe,”  he says. “With all the potential of well-established bean crops from the autumn, the current aim is to protect the new growth. So that when we get to ELATUS ERA timing for both chocolate spot and brown rust, from GS 51, there’s strong clean growth and good yield opportunity.”