Incidence and epidemiology of wood disease in Algerian citrus orchards

Abstract

The wood diseases are very damaging to the culture of citrus and many hosts around the world. It is considered as a complex pathosystem that requires the analysis of its various aspects. In this context, we conducted epidemiological and etiological studies. Our studies were conducted for four consecutive years (2017-2020) on 25 orchards from five localities in Algeria. The results of symptom diagnosis showed the presence of different categories of symptoms; these are the total and/or partial dieback. The examination of the cross-sections of infected wood showed the presence of different forms of inner necrosis. The isolations from the necrotic tissues of the infected trees put often in evidence the presence of a diversified fungal flora dominated by Botryosphaeriaceae fungi. We also recorded an overall infection rate of 23.28% representing a severity index of 1.77 on a scale of four degrees, giving an incidence of 10.76%. The overall assessment of the dieback situation in the studied orchards showed a rapid increase in all epidemiological indices. The statistical analyzes showed that the factors region, age, rootstock, type of irrigation and soil texture had a highly significant effect on the variation of epidemiological parameters. However, the factor year is only moderately significant. On the other hand, the factor cultivar, has no significant effect on these indices. The epidemiological behavior of dieback in these orchards confirms that the spread of the disease is favored by cultural techniques such as irrigation and pruning.