Microbial dynamics in the soil and presence of the avocado wilt complex in plots cultivated with avocado cv. Hass under ENSO phenomena (El Niño - La Niña)

The avocado wilt complex (AWC) is the most important disease. AWC development is highly dependent on climatic factors. The objective of this work was to determine the dynamics of beneficial and pathogenic microbe populations associated with AWC under standard climatic conditions and during ENSO (El Niño-La Niña) phenomena, as well as the incidence, severity and mortality of avocado plants caused by different causative agents of AWC. In three plots planted with avocado cv. Hass, external and within soil profile climatic variables (temperature, precipitation and soil moisture) were monitored using electronic devices. Beneficial populations of Pseudomonas spp., Thichoderma spp., and endospore- forming bacteria and pathogenic populations of Phytophthora cinnamomi, and Verticillium sp. were quantified. In addition, the amount of roots affected by the abiotic causal agent of AWC, hypoxia-anoxia, were evaluated. As complement, in 45 commercial plots, the influence of ENSO phenomena on epidemiological variables associated with the AWC was determined. The results of this research show that microbial populations in soils planted with avocado may be modulated by climatic variables especially the accumulated precipitation and moisture of soils, reducing beneficial and increasing pathogenic microbe populations. Under ENSO phenomena microbial populations in plots cultivated with avocado cv. Hass greatly varied together with incidence, severity and mortality of plants caused by AWC.