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Fungal canker pathogens of almond initiate infection in trees primarily through pruning wounds. Biological control agents (BCAs) have the potential to provide long-term protection of pruning wounds by colonizing the wound surfaces and underlying tissues. Laboratory and field tests were performed to assess the efficacy of various commercial and experimental BCAs as wound protectants against almond canker pathogens. Four Trichoderma-based BCAs were evaluated using detached almond stems in the laboratory against the canker pathogens Cytospora plurivora, Eutypa lata, Neofusicoccum parvum, and Neoscytalidium dimidiatum. Results indicated that Trichoderma atroviride SC1 and T. paratroviride RTFT014 significantly reduced infections by all four pathogens. The abilities of these four BCAs to protect almond pruning wounds against E. lata and N. parvum were further evaluated in field trials using two almond cultivars and during two consecutive years. Both T. atroviride SC 1 and T. paratroviride RTFT014 protected almond pruning wounds against E. lata and N. parvum as efficiently as thiophanate-methyl, the recommended fungicide for treatment of almond pruning wounds. Comparisons of different application timings of BCA in relation to pathogen inoculation revealed a significant improvement in wound protection when inoculations were conducted 7 days versus 24 h post-BCA application for N. parvum, but not for E. lata. T. atroviride SC 1 and T. paratroviride RTFT014 are promising candidates for the preventive protection of almond pruning wounds and for inclusion in integrated pest management programs and organic almond production systems. [ABSTRACT FROM AUTHOR]

Numerous fungal canker pathogens threaten almond production in California, causing high tree mortality and reducing orchard longevity. Pruning wounds are the main infection sites for these pathogens. This study aimed to identify the lowest risk period for pruning almond trees and to determine the duration of susceptibility of pruning wounds to fungal infections. During 2 years at two locations, pruning wounds were made monthly from September to January and inoculated with Botryosphaeria dothidea, Eutypa lata, Neofusicoccum parvum or Neoscytalidium dimidiatum, at 0, 1, 2, 3, 5 and 8 weeks after pruning. Pruning wounds were susceptible to infection by N. parvum and N. dimidiatum from September to December, with a significant decrease in susceptibility for wounds made in January relative to September. Fresh wounds had the highest probability of infection by N. dimidiatum, as wounds 1 week or older were less likely to be infected. Pruning month did not significantly impact wound susceptibility to B. dothidea; susceptibility decreased sharply with wound age. Wound susceptibility to E. lata significantly differed amongst pruning months, with pruning wounds of 1 week or older made in December and January being the least susceptible. These results indicated that delayed pruning in December and January can reduce the risks of canker pathogen infections compared to early pruning from September to November. This study showed that pruning wounds were most susceptible to infection during the first 2 weeks following pruning; thus, pruning wounds should be protected for at least 2 weeks shortly after pruning. [ABSTRACT FROM AUTHOR]

• Biological control agents were tested in the field in almond, cherry, and grapevine. • Trichoderma atroviride SC1 protected efficiently grapevine pruning wounds. • Clonostachys rosea J1446 protected efficiently almond and cherry pruning wounds. The ascomycete fungi that cause wood canker diseases in perennial, horticultural crops are often generalist pathogens able to infect multiple host plants. These pathogens frequently infect pruning wounds, and the protection of such wounds with chemicals or biological control agents (BCAs) is an essential component of disease management. This study aimed at assessing four commercial BCAs for their ability to prevent almond, cherry, and grapevine pruning wound infections by three canker pathogens under field conditions for two growing seasons: Calosphaeria pulchella in cherry, Neofusicoccum parvum in almond and grapevine, and Eutypa lata in all three hosts. The two bacterial BCAs tested, Bacillus amyloliquefasciens MBI 600 and Streptomyces lydicus WYEC 108, performed poorly overall as infection rates in treated wounds were not significantly different than in the water-treated wounds for most pathogens in all crops. Trichoderma atroviride SC1 provided the best protection against E. lata and N. parvum in grapevine, achieving superior or equivalent protection than the standard conventional chemical thiophanate-methyl. Field trials also demonstrated that Clonostachys rosea J1446 provided satisfactory protection of pruning wounds against E. lata and C. pulchella in cherry and against E. lata and N. parvum in almond trees. The identification of effective BCAs for use in multiple crops and against multiple pathogens is a great step towards a sustainable management of fungal canker diseases by mitigating the negative impacts of chemical fungicides. [ABSTRACT FROM AUTHOR]

Fatty acid methyl ester (FAME) analyses can be useful for distinguishing microbial species. This study conducted FAME analyses on 14 fungal species known to cause grapevine trunk diseases. FAME profiles were dominated by oleic acid, albeit profiles were characteristic enough to separate species. Discriminant analyses suggested that palmitoleic acid/sapienic acid, pentadecylic acid, and an unsaturated 17-carbon fatty acid (17:1ω8 c)could explain 79.8% of the variance in the profiles among species in the first three discriminant functions. FAME profile libraries were created for use in a commercialized software, which was able to accurately identify isolates to the species level, with a low rate (9.4%) of samples to be reassessed. Dendrograms created using neighbor-joining cluster analyses with data from FAME profiles were compared with those using internal transcribed spacer (ITS) region sequences. This revealed that FAME profiles, albeit useful for tentative species identification, should not be used for determining phylogenetic relationships because the dendrograms were significantly unconcordant. Regardless, these results demonstrated the potential of FAME analyses in quickly and initially identifying closely related fungal species or confirming conclusions from other species identification techniques that would require independent validation. [ABSTRACT FROM AUTHOR]