Article taken from Agronomist & Arable Farmer Magazine
A new early warning system for the notifiable disease fireblight is the latest to be added to Agrovista’s cloud based pest and disease forecasting service for top fruit growers, Growers Choice Interactive. The service, a first in the UK market, is available free of charge to GCI subscribers, says Agrovista fruit agronomist Alex Radu. “Fireblight is a potentially serious disease on apples and pears caused by the bacterium Erwina amylovora,” he explains. “There is no chemical cure, so growers have to rely on copper based preventative or antagonistic sprays, which makes accurate forecasting all the more vital.” The fireblight software calculates the likelihood of infection on blossom and new plant growth, as well as subsequent bacterial growth, based on temperature and relative humidity/rainfall. This information is gleaned from live data supplied by 40 fruit-specific weather stations across the country. “Erwina becomes a threat at 18 degrees or more, when conditions are wet,” Mr Radu explains.
“Growers whose orchards have a history of disease can assume it is there and we can now help them forecast potential outbreaks with greater accuracy. This means we can improve the timing and efficacy of preventative applications, which will be a real benefit to growers in managing disease. IT will also reduce the number of applications required and ensure that they are targeted more effectively, saving growers’ money and helping to reduce the presence of residues in the environment and the crop.”
The GCI package also includes RIMpro’s primary and secondary scab, codling moth and canker forecasts. Subscribers can access live graphics and text alerts are available for major events. Daily emails are also available for the local weather forecast, likely spraying conditions and spray application windows.
Fireblight Facts:
Fireblight is a notifiable disease. The most likely means of introduction is via infected material.
Hosts include wild shrubs related to apples and pears, notably hawthorn.
Primary infection occurs through lenticels or wounds in young shoots, or through blossom. The disease can spread to other plants via insects and birds, as well as wind and rain.
Suspicous symptoms include wilting and death of flower clusters, withered young shoots, shrivelled black fruits and necrotic patches on leaves.
Late flowering varieties are particularly susceptible as bacterial numbers build during the season. Older trees tend to be less susceptible.
The bar at the bottom of the screen, above right, shows leaf wetness readings in light blue and active rain as dark blue. The lower graph shows the growth of the Erwina population on the stigma after contamination. Each black line stands for a new group of flowers. The middle graph shows the potential infection incidence as calculated from flower age and level of the infecting bacterial population. The upper graph shows the growth within the plant of the Erwina population after infection. In this case, taken from an orchard in mid Europe, this weather during flowering was very favourable for the development of high Erwina population levels on the stigma. Six wetness events caused potential infection events. Since the earliest infections rarely result in symptoms, sprays can be adjusted depending on individual risk management preferences. Nonetheless, at least two sprays were needed to adequately manage fireblight – the first spray relation to the 20th April infection and a second spray for flower groups that opened later and which led to infection on 25th-28th April.