In recent years, favourable climatic conditions and growing immunity to bactericides have set the stage for an increase in bacterial blight in many Northwest cherry orchards. Last year's bacterial blight was described as the worst in 37 years by plant pathologist Gary Grove of Washington State University. Grove and colleague Youfu Zhao conducted a study of fungal pathogens in cherry orchards, identifying several pathogens, but highlighting bacterial cancer as the main threat.
Zhao analysed samples from 57 orchards, identifying the pathogen Pseudomonas syringae and checking for resistance to copper and kasugamycin. The results show widespread resistance to copper, and some strains show resistance to both treatments. Zhao emphasises the importance of cultural practices to minimise damage, as the inappropriate use of products could aggravate the situation.
To avoid infection, it is recommended to prune only in dry weather conditions, especially in summer, and to adopt strategies such as painting the trunks white to prevent winter injury. Winter pruning can be safe if conditions are dry, but for new plantings, headcuts during sensitive weather conditions can encourage infection.
Zhao recommends collecting samples for analysis if resistance is suspected in orchards. Copper resistance is widespread, and irrigating resistant strains can make the situation worse. Zhao has also identified a new risk, P. syringae pv. morsprunorum, but there is currently no indication that it is more dangerous.
Zhao has also identified two subspecies of P. syringae, further complicating the situation. For growers, the key is to understand that the bacterium overwinters in cankers and buds, spreading through wounds during wet conditions in spring and autumn. Bactericide resistance is a serious problem, and Zhao recommends practices such as pruning during dry times, especially in summer, and switching from sprinkler to drip irrigation to keep the environment as dry as possible.
Irrigation to induce bud break in spring is risky, and Zhao suggests planning carefully for weather conditions. Early leaf fall with chemical treatments can reduce the risk of infection in the autumn. Finally, Bishop, together with Zhao and Sallato, emphasises the importance of cultural practices in managing the disease, considering it manageable with careful orchard management.
Read the full article: Good Fruit Grower
Image: Good Fruit Grower
13 Sep 2024
According to Minister for Primary Industries Jane Howlett: “We know that gaining new markets will further grow the industry which is why our 2030 Strong Plan for Tasmania's future commits 600,000 dollars to Fruit Growers Tasmania to expand its commercial presence”.
15 Aug 2024
As far as the domestic market is concerned, according to data from SIMA GPP, there was a price increase in 2023 compared to the previous three-year period 2020-2022, especially in the last weeks of the campaign, where the price rose from around 3€/kg to around 4.70€/kg.
10 Mar 2025
Biostimulants, such as glycine betaine or biostimulants based on seaweed (e.g. Ecklonia maxima), can be a sustainable approach to improve the condition of plants, even under adverse environmental circumstances.
10 Mar 2025
The results of a recent study showed a significant reduction in bird damage in covered rows compared to uncovered ones. Furthermore, measurements of fruit quality showed no significant differences.
