Prune, Plum, and Nectarine as Hosts of Trichothecium roseum in California Orchards

Trichothecium roseum (Pers.:Fr.) Link was frequently observed (up to 21%) on mummified peach (Prunus persica (L.) Batsch), nectarine (P. persica (L.) Batsch var. nectarina (Aiton) Maxim.), plum (P. salicina Lindl.), and prune (P. domestica L.) fruits in orchards during a 1995 to 1996 survey. Pink mold rot caused by T. roseum was also frequently observed (at about the 1 to 2% level) on a number of samples of prune fruit collected from commercial orchards in Glenn, Butte, Madera, Fresno, and Tulare counties in 1996, after storage at 4°C for 7 days and then 20°C for 4 days. Wounded and nonwounded prune (cv. French), plum (cv. Casselman), peach (cv. Fairtime), and nectarine (cv. Spring Bright) fruits were infected after inoculation with a drop (20 μl) of T. roseum suspension (5 × 10⁵ conidia/ml). Characteristic pink sporulation covered the surface of most fruit 7 days after inoculation. Conidia of T. roseum completely covered all wounded and nonwounded prune fruit, sparsely on the wounded plum fruit, and densely on both wounded and nonwounded peach and nectarine fruits (lesion diameter = 1 to 7 cm) 2 weeks after inoculation. T. roseum sporulated more rapidly and better on the fruits that were contaminated with either Monilinia fructicola (G. Wint.) Honey, or a Cladosporium sp. Peach has been listed as a host of T. roseum (California Plant Disease Host Index, Part 1: Fruits and Nuts, A M. French, ed., 1987), but this is the first report on the pathogenicity of this fungus on prune, plum, and nectarine from California.