INDUSTRY NEWS
Monterey decline under investigation
ABOVE : Plant pathologist Len Tesoriero collecting twigs for pathogenic sampling for Monterey decline , which has been widespread this season . INSET : Symptoms of Monterey decline .
NATIONALLY 6,675 hectares of Monterey is planted , making it Australia ’ s third most popular almond tree , but there ’ s been widespread decline in the variety this season . The issue was first reported in 2017 . Symptoms vary from significant leaf bud failure or delayed leaf out , followed by shoot dieback that can progress to affect the whole limb or tree . Plant pathologist Len Tesoriero is investigating the issue but he ’ s got more questions than answers . “ We need to examine it a bit more to see what ’ s typical and atypical ,” he said . A more holistic study has started to resolve potential physiological causes and develop effective preventable and management options . Dr Tesoriero is looking for more case studies , including young and healthy orchards to try and prevent it from developing . “ We ’ ve just skimmed the surface ,” he said . Dr Tesoriero is trying to rule out plant pathogens . Tests for Phytophthora trunk rot and Pseudomonas syringae bacterial blight have been negative . It ’ s likely the internal trunk necrosis ( death of heartwood ) is associated with anoxic ( oxygen deprived ) conditions as trees receive excess water compared with healthy alternate row varieties . Waterlogged soils in the wet weather last season would also have caused low oxygen levels and caused death of fine feeder roots . Larger roots appear to be healthy , while finer feeder roots are in a poor condition . Riverina surveys In September samples were collected from nine farms in the Riverina . They were cultured for fungi , oomycetes and bacteria from stem , trunk and roots , but so far there have been no consistently recovered pathogens . The fungi and bacteria from the recent surveys are still to be identified but a number of potential fungal and bacterial pathogens have been isolated previously in preliminary surveys . The Californian experience Dr Tesoriero said almond growers in Calilfornia aren ’ t too concerned about the decline in Monterey because their trees aren ’ t dying .
Len Tesoriero collects heartwood for analysis .
“ There ’ s leafing and / or bud failure in some seasons but the plants generally recover , and growers aren ’ t seeing significant shoot dieback ,” he said . In California , Monterey decline is thought to be a physiological condition associated with cool wet springs and tree stress during summer . Compared to other almond varieties Monterey appears to accumulate a lower concentration of sugars when measured just after harvest . It ’ s been suggested that Monterey trees planted on heavy soils and where there ’ s poorer drainage are more affected . Overseas experts also suspect several minor pathogens could be associated with secondary rots . Next steps Dr Tesoriero said potential management strategies for the coming seasons could include some or all of the following :
• Balancing canopy growth – pruning , hedging to avoid willowing habit and open up canopy
• Improve drainage – gypsum and ripping outside drip lines
• Use of root stimulating products – microbials , organic emulsions , seaweed extracts
• Plant defence activators – phosphorus acid and chelated micronutrients
• Focus on fungicide programs for shoot protection .
industry . australianalmonds . com . au
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