Growers are being advised to monitor winter bean crops as harsh weather conditions haveincreased the potential to develop chocolate spot, risking reduced yield or crop failure.
Early drilling and harsh winter weather combined with cool, wet conditions in spring increase winter beans vulnerability to?chocolate?spot. Caused by at least four species of the?botrytis?pathogen, the disease can cause yield losses of 25 per cent. In very severe cases,?chocolate?spot can completely destroy a crop, according to BASF.
Weather conditions through March will have stopped early spring recovery and increased disease risk, exacerbated by where rain splash has spread chocolate spot spores from existing lesions on lower leaves, onto new growth, says Simon Jackson, Syngentas technical manager.
Trace elements
Field assessments conducted by Syngenta indicate crops that are looking particularly stressed and struggling could well benefit from supplementary trace elements, principally manganese and magnesium, along with zinc.
With rapid compensatory growth in warmer conditions, crops are expected to quickly build big canopies which tend to make them more susceptible to chocolate spot as the season progresses.
Slow progress for spring bean crops so far this season will focus agronomy on providing adequate nutrition to increase plant stand and prolong growth for as long as possible, along with disease control for green leaf retention to boost yields, says Mr Jackson.??
Depending on disease pressure, most spring crops still benefit from a two-spray foliar disease programme, he concludes.
Top tips for chocolate spot control
- Monitor crops closely for first signs of disease
- Keep an eye on the forecast for cool and humid conditions
- Use a fungicide with protectant activity
- Ensure applications are timely at the first signs of disease or early flowering. Follow up 3-4 weeks later
- At application, where canopies are dense, keep spraying speeds low and water volumes up.
Source: BASF
