How to Manage Pests
UC Pest Management Guidelines
Cut Out (Blackeyes)
(Reviewed 8/07, updated 12/08)
In this Guideline:
Cut-out or more correctly 'early-cutout' is when a large percentage of the plants simply senesces and then dies after the first flush of pods, usually beginning about 80 days after planting. The most common aboveground symptoms are that of early leaf senescence and defoliation. No new leaves or blooms occur at the buds, which may turn brown and abort.
Cut out should be considered a complex of symptoms rather than a specific disease. It may be caused by pathogens, or it may be a physiological response. It eliminates the possibility of additional podding, thereby shortening the season and potentially reducing yields by about 15 or more cwt/ac. A combination of a strong first set, variety, unknown soil pathogens and environmental factors seem to trigger the expression of cut out.
The soil pathogens F. oxysporum f. sp .tracheiphilum (Fusarium wilt), F. solani (Fusarium root rot), or Thielaviopis basicola may cause premature senescence of blackeyes. Infections by these organisms can be differentiated by symptoms. Fusarium wilt causes discoloration in the vascular system that extends from the roots into the aboveground stems and petioles (see FUSARIUM WILT). Fusarium solani causes rust-colored lesions on roots. Thielaviopsis root lesions are dark brown-black in color. Other pathogens that occur less frequently on roots of plants exhibiting early cut out are Macrophomina phaseolina, Rhizoctonia solani, and Phytophthora drechsleri.
For physiological cut out avoid water stress to the plants after bloom. For Fusarium wilt, choose a resistant variety. For diseases caused by F. solani and Thielaviopsis, crop rotation will help p revent the build up of these pathogens in soil. Cut out appears to be more severe when plants are stressed by over or under irrigation or by soil compaction, so follow good water management practices, especially during reproductive growth, and avoid compacting the soil.
UC IPM Pest Management Guidelines:
R. M. Davis, Plant Pathology, UC Davis
Acknowledgment for contributions to Abiotic Disorders:A. E. Hall, Botany and Plant Sciences, UC Riverside
Acknowledgment for contributions to Diseases/Abiotic Disorders:S. R. Temple, Plant Sciences, UC Davis
Acknowledgment for contributions to Diseases (viruses):R. L. Gilbertson, Plant Pathology, UC Davis