The Influence of Carrot Plant Control Against Alternaria Blight on the Root Health Status After Storage

A good health status and quality of roots during winter storage especially in soil clamp is a serious economic problem. The proper plant protection in the field can reduce the occurrence of pathogens mainly those infecting at first leaves and then causing root rots such as fungi of Alternaria species. During 2005-2006 the studies on carrot protection against Alternaria blight were conducted in Mydlniki near Kraków. Carrot plants were sprayed with solutions of following control agents: liquid extract of garlic 100% (Bioczos) at the concentration of 2%, chitosan - 20% (Biochikol 020 PC) at the concentration of 2% and extract from grapefruit 33% (Biosept 33 SL) at the concentration of 0.2%. As comparative fungicide azoxystrobin 250 g.L^-1 (Amistar 250 SC) at the dose of 0.8 L·ha^-1 was used. The healthiness of roots was examined twice, first time directly after harvest and the second time after the storage in the spring. The results revealed that the carrot plant protection against Alternaria blight with the examined control agents reduced infestation of leaves and in the consequence improved the root health status. The analyses carried out in April 2006 and 2007 after root storage showed the significant differences among examined treatments, both in the range of root infestation as well as in the losses of root weight. The lowest root infection was observed in the treatments sprayed with the grapefruit extract. Besides the protection of plants during growing season had an influence on the root weight losses.

There was no clear effect of a specific treatment on the total yield of carrot, but a tendency of a higher crop from the plots treated with fungicides was noticed as compared to the untreated control. A significant influence of applied agents was visible after the storage period. The lowest root weight losses were observed from the treatments protected with chitosan and grapefruit extracts. Untreated control produced the highest weight losses of roots in both years of experiment. Laboratory tests revealed numerous colonies of fungi and bacteria on the diseased carrot tissues. Dominating microorganisms were fungi from Alternaria and Fusarium genus.