First Report of Botryotinia Blight of Asiatic Hybrid Lily Caused by Botryotinia sphaerosperma in North America

In November 2002, a disease was observed on eight cultivars of Asiatic hybrid lilies (Lilium sp.) in two fields in Carpinteria, CA. The same disease was observed on greenhouse grown Asiatic hybrid lilies in Nipomo, CA in an adjacent county. ‘Monte Negro’ was the most severely affected. Symptoms consisted of necrotic leaf tips as well as 5- to 10-mm ellipsoidal necrotic spots on stems and the abaxial and adaxial leaf surfaces. Lesions were initially dark brown and water soaked, becoming lighter as they dried. Although leaf spot symptoms usually began at the leaf tip, eventually the entire leaf would become blighted. Disease symptoms were not observed on Oriental hybrid lilies in the same nurseries. A Botrytis sp. was consistently associated with the disease symptoms. In pure culture, the fungus matched the description of Botryotinia sphaerosperma (Gregory) Buchw. (anamorph Botrytis sphaerosperma (Gregory) Buchw.) (1). The fungus is distinguished by its large, spherical conidia that average 23 to 25 μm in diameter at maturity. The conidia are born in compact heads on unbranched conidiophores. Conidia and conidiophores are hyaline when young. At maturity, the conidia turn dark brown, whereas the conidiophores turn blackish brown. The fungus formed abundant sclerotia on potato dextrose agar when incubated at room temperature with 12 h per day of fluorescent lighting. The sclerotia were black, ovate to sphaeroidal, had a rough surface, and were 1.5 to 2.5 × 1 to 2.5 mm. Apothecia were not observed. Pathogenicity was tested on 12 Asiatic hybrid and 12 Oriental hybrid lilies. Inoculum consisting of mycelial fragments and conidia (1 × 105 conidia per ml) was produced on lily leaf agar (500 ml of H2O, 7.5 g of agar, and 25 g of healthy, macerated lily leaves). Plants were inoculated by rubbing leaves and stems with the spore and mycelial fragment suspension using cotton swabs. Plants were maintained in a greenhouse at 25°C. After 7 days, characteristic lesions were observed on the leaves and stems of Asiatic hybrid and Oriental hybrid lilies, from which the same Botrytis sp. was consistently isolated. Three control plants each of Asiatic hybrid and Oriental hybrid lilies treated with water as a check, remained symptomless. Although studies to determine potential fungicides for controlling this pathogen have not yet been undertaken, good sanitation, a lily-free period, and steam sterilization of beds should be considered in the management of this disease. In Europe, this fungus has been reported as a pathogen on Lilium regale (2). To our knowledge, this is the first report of this pathogen in North America. Herbarium specimens were submitted to the USDA APHIS mycology laboratory in Beltsville, MD (Accession No. BPI 842231). Cultures were also submitted to the American Type Culture Collection (MYA-2890). References: (1) P. H. Gregory. Trans. Br. Mycol. Soc. 25:26, 1941. (2) G. L. Hennebert. Friesia 9:52, 1969.

Influence of Frozen Storage Duration and Forcing Temperature on Flowering of Oriental Hybrid Lilies

The effect of long-term storage of lily bulbs at -2 °C (frozen storage) and of high forcing temperatures on plant height and floral abnormalities was investigated with Oriental hybrid lilies from 1998 to 2000. `Acapulco' and `Simplon' bulbs were stored frozen at -2 °C for various lengths of time and were forced in fan- and pad-cooled greenhouses with temperatures ranging from 11 to 31 °C, depending on the season. The same cultivars were also forced in greenhouses and maintained year-round under refrigerated air conditioning with day/night temperatures of 16/15.5 °C or 18.5/18 °C. Floral development immediately after storage and at different intervals thereafter was observed by scanning electron microscopy (SEM). The prolonged frozen storage reduced the number of flowers. High greenhouse forcing temperatures during summer significantly accelerated flowering, resulted in short plants, and increased the number of abnormal flowers. Forcing at a low temperature (15.5 °C) after planting the frozen stored bulbs resulted in longer cut stems than those forced at 25 °C for 30 days after potting. Bulbs can be stored up to 9 months and still produce high-quality Oriental hybrid lilies.

265 Influence of Frozen-in Storage Duration and Forcing Temperature on Flowering of Oriental Hybrid Lilies

The effect of long-term storage of lily bulbs at -2 °C and of high temperatures on plant height and floral abnormalities was investigated with Oriental hybrid lilies in 1997-2000. `Acapulco' and `Simplon' bulbs were stored frozen at -2 °C and forced in regular greenhouses with varying temperatures between 12 to 30 °C, depending on the season, and also air-conditioned greenhouses where temperatures were maintained year-round at 15.5 to 16 °C or 18 to 18.5 °C. Floral development was observed under a scanning electron microscope after -2 °C treatment. At flowering, stem length with dried and green leaves, number of leaves, and number of normal and abnormal flowers were counted. Although frozen-in storage duration affected plant height, flowering, and the number of abnormal flowers, high temperatures during summer significantly affected the speed of flowering, plant height, and the number of abnormal flowers. High temperature damage can be prevented by growing bulbs at low temperatures immediately after planting the frozen-in stored bulbs. Bulbs can be stored for 12 months to produce quality cut Oriental hybrid lily flowers.

Postproduction Evaluations of Potted Asiatic and Oriental Hybrid Lilies

Potted Lilium Asiatic hybrids `Aristocrat', `Horizon', and `Polka' were evaluated following 3, 6, or 9 days of transport at 2, 7, or 13C. `Aristocrat' and `Horizon' withstood transport with little or no effect on floral bud opening. `Polka' was the most sensitive cultivar to transport, where bud opening decreased 33% when transported at 13C for 9 days. Most floral buds opened on `Aristocrat' (90% to 98%), while fewer buds opened on `Horizon' (37% to 56%) and `Polka' (52% to 90%). Individual flower longevity and diameters were largely unaffected by transport. Plant longevity was reduced 4 to 7 days when transported for 9 days at ≥7C or for >3 days at 13C. Plant longevity averaged 16 days for `Aristocrat' and `Polka' and 12 days for `Horizon'. `Aristocrat' and the Oriental potted hybrid lily `Star Gazer' were maintained at postproduction conditions of 18, 21, or 24C at 7 or 14 μmol·m–2·s–1 after being commercially transported for 4 days at 5 ± 2C. Postproduction conditions had no effect on floral bud opening of `Aristocrat' (98% to 99%), while bud opening of `Star Gazer' was reduced 17% at 24C compared to 18C. Plants lasted 4 and 9 days longer at 18C than at 21 or 24C, respectively. Foliar discoloration was greatest at 24C. Irradiance level had no effect on the variables evaluated.