Articles
Green mould control under lower fungicide residue limits on citrus
Article number
1451_33
Pages
227 – 232
Language
English
Abstract
The maximum residue of traditional fungicides used to control postharvest diseases of citrus fruit are under review and could be lowered.
These fungicides, if applied at lower dosages, may have reduced efficacy against postharvest diseases such as green mould.
This study therefore focused on the control of green mould under lower fungicide dosages when combined with generally recognised as safe (GRAS) chemicals. ‘Eureka’ lemon fruit were wound-inoculated the day before treating the fruit with the fungicides applied alone, at South African registered dosages, as well as at lower dosages, applied alone and in combination with postharvest GRAS chemical formulations (carbohydrate derived fulvic acid (CHD-FA, 0.53%) and potassium sorbate (0.3-0.75%)). The fruit were evaluated for green mould 14 days after inoculations.
Potassium sorbate combined with lower dosages of pyrimethanil (500 ppm; 95.83±4.56% control), showed significant increased control of green mould compared to when pyrimethanil was applied alone at the registered dosage (1000 ppm; 61.11±16.39% control). Similarly, potassium sorbate applied with lower dosages of azoxystrobin (843.75 ppm; 95.83±4.56% control) significantly increased control of green mould compared to when azoxystrobin was applied alone at the registered dosage (1125 ppm; 66.67±20.41% control). Carbohydrate derived-fulvic acid and potassium sorbate applied with lower dosages of imazalil increased control, although not statistically higher.
The same was true when CHD-FA was applied with lower dosages of thiabendazole.
These chemical combinations may be used to increase control of green mould, and reduce resistance development of postharvest pathogens at lower fungicide dosages.
Further studies will be conducted to determine resistance development of postharvest pathogens to these chemical combinations.
These fungicides, if applied at lower dosages, may have reduced efficacy against postharvest diseases such as green mould.
This study therefore focused on the control of green mould under lower fungicide dosages when combined with generally recognised as safe (GRAS) chemicals. ‘Eureka’ lemon fruit were wound-inoculated the day before treating the fruit with the fungicides applied alone, at South African registered dosages, as well as at lower dosages, applied alone and in combination with postharvest GRAS chemical formulations (carbohydrate derived fulvic acid (CHD-FA, 0.53%) and potassium sorbate (0.3-0.75%)). The fruit were evaluated for green mould 14 days after inoculations.
Potassium sorbate combined with lower dosages of pyrimethanil (500 ppm; 95.83±4.56% control), showed significant increased control of green mould compared to when pyrimethanil was applied alone at the registered dosage (1000 ppm; 61.11±16.39% control). Similarly, potassium sorbate applied with lower dosages of azoxystrobin (843.75 ppm; 95.83±4.56% control) significantly increased control of green mould compared to when azoxystrobin was applied alone at the registered dosage (1125 ppm; 66.67±20.41% control). Carbohydrate derived-fulvic acid and potassium sorbate applied with lower dosages of imazalil increased control, although not statistically higher.
The same was true when CHD-FA was applied with lower dosages of thiabendazole.
These chemical combinations may be used to increase control of green mould, and reduce resistance development of postharvest pathogens at lower fungicide dosages.
Further studies will be conducted to determine resistance development of postharvest pathogens to these chemical combinations.
Authors
M. van Dyk, H. Kellerman, J.M. van Niekerk
Keywords
carbohydrate derived-fulvic acid, Penicillium digitatum, postharvest, potassium sorbate, citrus decay
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