RESEARCH & EVENTS
US expert shares almond disease tips
32
ASSOCIATE Professor of Cooperative Extension Florent Trouillas from the University of California , Davis , toured Australia ’ s almond growing regions during November . The plant pathologist who works with pistachio , olive , almond , cherry and walnut crops provided an insight into his role and the work he ’ s doing in California , which includes both laboratory and diagnosing problems in the field research to diagnose and manage disease problems . " Whenever pest control advisors or farmers see problems they don ’ t understand , we need to go into the field and try and get an understanding of what ’ s happening in the orchard to work out what might be causing the problem . We also process a lot of samples on a regular basis ,” he told attendees at the recent ACE open day . “ It ’ s important to understand what pathogens are involved because they have different biology .” Associate Professor Trouillas is at the forefront of disease observation and has spent many years researching almond canker diseases . “ These fungal diseases which kill wood and cause gumming are often associated with pruning wounds on the trunks or cracks at the tree crotch ,” he said . “ They lead to branch dieback and tree death , especially when they happen in young orchards .” His laboratory has been conducting wound protection trials and Associate Professor Trouillas says the results are exciting . “ We ’ ve tested more than 25 chemicals , biocontrol agents , sealants and pastes to improve the protection of pruning wounds ,” he said . At the moment the focus has been to identify a biocontrol agent that could protect pruning wounds . “ The natural fungi Trichoderma can colonise and establish in the wood , preventing fungal canker pathogens from infecting pruning wounds ,” he said . The product Vintec ( Trichoderma atroviride SC1 ) originating from Europe and is now distributed and registered in the US for almond , and provides good protection of pruning wounds . “ It can be applied using conventional airblast sprayers onto almond pruning wounds and protect them ” he said .
In A Nutshell - Summer 2023 Vol 24 Issue 4
Associate Professor Florent Trouillas inspects almond trees for any sign of disease .
In the US this is done at a rate of 100 gallons per acre . This year was the wettest year on record in California which led to outbreaks of Phytophthora . Associate Professor Trouillas said Phytophthora is a soil borne disease , that has the ability to move through water and saturated soil . “ It gets in orchards through irrigation from surface water or following flooding , and causes diseases including root rot which leads to the slow decline of trees or crown rot which kills trees rapidly ,” he said . When almond trees are planted , the bud union needs to be well above the soil surface otherwise the susceptible scion can develop Phytophthora infection . He said foamy canker tends to follow an old Phytophthora infection , but it ’ s also suspected that damage on the trunk such as sunburn or herbicide injury also could lead to foamy canker . Perennial or aerial Phytophthora leads to profuse gumming near the tree crotch where there ’ s been poor scaffolding selection allowing pockets of water and debris to accumulate . Associate Professor Trouillas said Phytophthora syringae , which is found in Australia , is extremely aggressive to almond . While it can infect pruning wounds , it has also been shown to infect almond trees at twigs , killing the twigs and progress into large scaffold branches . Associate Professor Trouillas said if you have a Phytophthora infection the gumming will be profuse and the disease spreads fast within a tree .