Abstract
Under field, greenhouse and laboratory conditions, the study evaluated the mite-fungus-yellowing association in the Welsh onion Allium fistulosum, in recently established and mature crops, in the localities of San Francisco and Alianza (Pasto, Colombia), located at 2650 m elevation, with a temperature of 12°C and an average annual rainfall of 1100 mm annual. In recently established crops, the incidence of yellowing was 11.0% and 14.2%, respectively, with no difference between localities. Similarly, there were no significant difference between localities for the mature crop, with an incidence of 38.4% and 43.40%, respectively. In the sampling at each locality two kinds of mites were found which are responsible for the yellowing of onion, Rhizoglyphus echinophus and Rhizoglyphus vincatus (Acari: Acaridae), being R. echinopus with the greatest percentage of affected plants (56.7%). The fungi responsible for the damage to the onion crops were: Phoma sp., Botrytis sp., Gliocladium and Fusarium oxysporum. In the greenhouse the greatest percentage of affected plants had F. oxysporum (43.3%) and the complex F. oxysporum and Phoma sp. (40.0%). The association of the mite R. echinopus and the fungus F. oxysporum, produced the greatest percentage of affected plants (80.0%). Moreover, R. echinopus was found to present the most descendents when in the presence of F. oxysporum (78 individuals in 72 hours).
Get full access to this article
View all access options for this article.