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First Report of Ovulariopsis on Lupinus havardii

In 1998 and 1999 a severe powdery mildew was observed in Las Cruces, NM, on Big Bend Bluebonnets (Lupinus havardii) grown in the greenhouse for cut flowers and vase life studies. An undescribed powdery mildew has been reported on L. havardii (2), but it has been observed only occasionally on leaves and has not cause a severe problem. The powdery mildew observed in Las Cruces began in March and caused severe infection from May through July. The disease spread rapidly due to movement of the pathogen during pruning operations and the close proximity of plants. Plants were heavily infected when no fungicide was applied. Plants were sprayed with the fungicide azoxystrobin, with best control obtained at 687 mg/liter of water. When an infected plant was used as a source of inoculum, disease spread rapidly to healthy plants placed around the infected plant. Infected leaves had chlorotic lesions that later became necrotic. Mycelia, conidiophores, and conidia of the pathogen were observed on leaves and occasionally on petioles and stems. Ellipsoid cylindrical-to-clavate conidia were hyaline, one-celled, and measured 49 to 68.1 μm × 12.2 to 14.7 μm. Conidia were produced on upright, simple conidiophores measuring 171 to 245 μm × 4.9 to 7.3 μm. Fibrosin bodies and cleistothecia were not found. The fungus was identified as an Ovulariopsis sp. (1). This is the first documented report of an Ovulariopsis sp. on L. havardii.

References: (1) U. Braun. Beih. Nova Hedwigia 89:1, 1987. (2) W. A. Mackay and T. D. Davis. HortScience 33:348, 1998.