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Damping-off is regarded as one of the most serious risks to pine plantations and the disease poses a potentially devastating threat to the future sustainability of the South African softwood industry. In spite of numerous prevention methods being tested, no absolute means of controlling the fungus is available to nurseries. In this study, 10 commercially available essential oils were assessed in vitro for their antifungal activity against four strains of Fusarium . Considering the efficacy, as reflected by the MIC values obtained, cost and availability of the essential oils, lemongrass is proposed as the most promising candidate for an in vivo study, first on a small scale and then under commercial conditions. [ABSTRACT FROM AUTHOR]

Together with Penicillium moulds, Geotrichum citri-aurantii (sour rot) is a major cause of citrus fruit decay. Fifty-nine commercially available essential oils and some of their major components were screened to determine their effects on the mycelial growth of G. citri-aurantii using toxic medium assays. Nine of these essential oils totally inhibited the mycelial growth of the pathogen at 1000 μl/l. Gas chromatographic analysis revealed the compositions of the most effective oils. Exposure to the vapours of selected essential oils ( Thymus vulgaris, Citrus aurantium var. amara, Cymbopogon citratus, Cymbopogon martinii, Origanum vulgare, Geranium graveolens roseum Bourbon) proved fungistatic, rather than fungicidal, towards the pathogen. ‘Valencia’ oranges, inoculated with G. citri-aurantii , were treated with the most promising botanicals. Essential oils (1000 μl/l) of C. citratus, C. martinii, O. vulgare and G. graveolens roseum Bourbon, incorporated into coating or applied as a curative dip, resulted in a drastic reduction in decay when compared to the negative control. No physiological breakdown of the fruit was evident at this concentration. C. citratus (lemongrass) was selected as the most cost-effective option for control of G. citri-aurantii. Previous commercial trials indicated the protective properties of Mentha spicata essential oil against Penicillium digitatum. To develop an effective multi-target protection product against G. citri-aurantii, P. digitatum and Penicillium italicum , essential oil of C. citratus was combined with that of M. spicata . A toxic medium, containing both essential oils, each at 750 μl/l, totally controlled all three pathogens. Although individual essential oil-amended coatings have previously been applied for postharvest control, this study proposes a mixture of these essential oils for control of two serious citrus pathogens ( G. citri-aurantii, P. digitatum ), in addition to P. italicum . [ABSTRACT FROM AUTHOR]

Abstract: Proliferation of fungal pathogens, such as Mycogone perniciosa, can severely affect the yields of cultivated mushrooms, including that of the button mushroom, Agaricus bisporus. A reduction in the number of fungicidal products approved for commercial application is currently providing new challenges to the mushroom industry. Forty essential oils, seven pure terpenoids and one phenylpropanoid were screened in vitro to determine the abilities of these substances to inhibit the growth of M. perniciosa. The fungal growth medium of both A. bisporus and M. perniciosa was supplemented with each test substance at a concentration of 50μL/L. Ten essential oils were further investigated at lower concentrations ranging from 5 to 40μL/L. The main components of these oils were determined by GC–FID and GC–MS. Lemon verbena (Lippia citriodora), lemongrass (Cymbopogon citratus) and thyme (Thymus vulgaris) oils were found to substantially inhibit the growth of the pathogen, while demonstrating lower toxicity towards A. bisporus than any of the other oils tested. A preliminary in vivo trial using M. perniciosa-inoculated casings revealed that the preventative use of lemon verbena or thyme oils was able to control the development of the disease. A commercial trial using these oils, as well as two of their main components (nerol and thymol), at a concentration of 40μL/L, revealed that none of these treatments were detrimental to the growth of the A. bisporus and an overall yield similar to that following application of a commercial fungicide (Chronos 450 SC) was obtained. These results suggest that essential oils or mixtures of selected pure components of essential oils may in future find application in button mushroom production, either as a substitute for synthetic fungicides or as an additional protective measure. [ABSTRACT FROM AUTHOR]

Abstract: Listeria monocytogenes is a Gram-positive bacterium, able to survive and grow in water, soil, agricultural products, various foods and the food-processing environment. The ubiquitous nature of the organism, coupled with its ability to colonise food-processing surfaces by forming biofilms, causes it to be of a major concern to the industry. Increased foodborne pathogen resistance and negative consumer perceptions regarding the use of synthetic bacteriocides, has resulted in natural antimicrobials being sourced from the plant kingdom. The listerial antibiofilm activities of Syzygium aromaticum (clove), Mentha spicata (spearmint), Lippia rehmannii and Cymbopogon citratus (lemongrass) essential oils and their major components were evaluated using the crystal violet assay and confocal scanning laser microscopy. Listerial biofilms treated with S. aromaticum or M. spicata essential oils, or the pure compounds nerol and citral, exhibited a similar biofilm biomass to the positive control. However, the essential oils of lemongrass, L. rehmannii, eugenol and R-carvone caused biofilm enhancement, rather than inhibition. L. rehmannii and lemongrass essential oils did not display any antibiofilm properties. Results obtained were confirmed by microscopic observations indicating either a reduction (inhibition) or an increase (enhancement) in biofilm biomass when exposed to the essential oils or pure compounds. The present study revealed that M. spicata and S. aromaticum essential oils as well as pure citral and nerol are good candidates for further development of ecofriendly disinfectants. [ABSTRACT FROM AUTHOR]