Biology and control of Neofabraea leaf spot, branch canker and twig dieback of oil olives in California

During the winter and spring of 2016, severe defoliation as well as twig dieback and branch cankers were observed in super-high-density oil olive orchards in California. Cankers developed at wounds caused by mechanical harvest.  Necrotic leaf spots were also detected commonly within the diseased orchards. Results of isolation revealed two species of Neofabraea to be consistently isolated from the symptomatic tissues. To date little is known about Neofabraea disease in olive. The emergence of this new disease in California olives is of major concern to growers and constitutes a serious threat to the industry’s productivity. The present project proposes to investigate various aspects of the new disease biology including disease etiology and epidemiology, pathogen biology, host susceptibility as well as strategies to control the disease and limit its spread.

 


Trunk and Scaffold Canker Diseases of Almond in California

Trunk and Scaffold Canker Diseases (TSCD) of almond cause significant yield and tree losses within orchards in California. Symptoms of TSCD include discoloration of vascular tissues, wood necrosis and gumming. Dieback of scaffold branches can occur and eventually the whole tree may die. Canker diseases are rather common in older orchards but concerns have raised among growers and farm advisors as TSCD diseases are also being detected in relatively young trees. In California, the main causes of TSCD are still poorly understood and diagnosis has been particularly difficult. Poor understanding of TSCD has also hindered attempts to control them. Our research efforts intend to characterized the main fungi associated with TSCD in California, evaluate their pathogenicity in almond cultivars and provide control strategies by testing various fungicides, bio-control agents and wound sealants for pruning wounds protection.

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Re-examination of Ceratocystis canker of almond in California

Ceratocystis canker of almond caused by Ceratocystis fimbriata occurs throughout almond production areas of California. The canker develops on trunks and branches of trees that have been damaged by tractors and harvesting equipment. There is a strong correlation between shaker damage and Ceratocystis canker presence. The fungus is spread by sap-feeding beetles and the resulting cankers can girdle the limbs, scaffolds and trunks of almond trees.  Despite its prevalence in California orchards, little research has been conducted on the pathogen’s biology and dispersal in California. The lack of research may be due to the difficulty in culturing this microorganism and because of this, diagnosis of this disease might have been overlooked. The lack of chemical or biological control practices is becoming problematic as Ceratocystis canker is one of the most common diseases found in California almond orchards. Research on this disease is coming at a critical time as the almond industry in California is growing rapidly. The purpose of our research is to improve diagnostics of Ceratocystis canker of almond, determine the population genetic diversity and spatial distribution of Ceratocystis fimbriata in almond orchards , and define management practices using cultural and chemical/biological solutions.

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Investigating new and emerging diseases of pistachio in California

We are investigating fungal diseases of pistachio including canker and crown rot diseases. New fungal pathogens associated with cankers have included Cytospora, Phomopsis, Phoma, Phaeoacremonium and Colletotrichum species. Pathogens associated with crown rots include Phytophthora as well as numerous Fusarium species. Ourcurrent objectives are to investigate the taxonomy and pathogenicity of the newly discovered fungal pathogens.  The ultimate goals of this project are to gain knowledge on diseases currently affecting pistachio trees and improve management strategies by improving pathogen detection and disease diagnosis within the UC Cooperative Extension.

Ring Test Results

 


Etiology and management of sweet cherry canker diseases

In the past, surveys for canker diseases in sweet cherry were mostly conducted in Northern and Central California. However, in these last years the sweet cherry industry has developed considerably in Southern counties such as Fresno, Tulare and Kern counties. Growers from these counties have expressed concerns regarding canker diseases. This year we proposed to extend surveys and assess the epidemic of canker diseases in sweet cherry orchards in the southern producing regions. Surveys are now underway. In Fresno Co, Calosphaeria pulchella appears to be the main pathogen associated with cankers and branch dieback, followed by Leucostoma persoonii, Eutypa lata and Schizophyllum commune. Surveys will continue in 2016.

Ring Test Results