Factors Affecting Cross-Protection in Control of Fusarium Wilt of Tomato. L. A. Wymore, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523. Ralph Baker, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523. Plant Dis. 66:908-910. Accepted for publication 1 February 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-908.

Cross-protection by the introduction of Fusarium oxysporum f. sp. dianthi into host tissue of tomatoes (Lycopersicon esculentum) susceptible to F. oxysporum f. sp. lycopersici was successful; however, the biocontrol agent was only effective when it was applied a few days before a challenge inoculation with the pathogen. Protection (manifested as a reduction in symptom expression) was apparent after 24 days when F. oxysporum f. sp. dianthi was used as the biocontrol agent but not 34 days after the challenge inoculation. The inoculum density of the cross-protection agent required for biocontrol was approximately equal to or higher than that used in the challenge inoculation with the pathogen. The results suggest that the use of cross-protection for biocontrol of Fusarium wilt of tomato is not effective under greenhouse conditions.

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