Disease Note

Rot of Oleander Cuttings Caused by Calonectria crotalariae. L. Pierce, Department of Plant Pathology, University of California, Berkeley 94720. A. H. McCain, Department of Plant Pathology, University of California, Berkeley 94720. Plant Dis. 70:352. Accepted for publication 9 December 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-352c.

Calonectria crotalariae (Loos) Bell & Sober caused basal stem rot of oleander (Nerium oleander L.) rooted cuttings. Wilting, the first symptom, was followed by brown rot that progressed upward from the cut end of the stem. Dark and light brown zonations were visible on the stem. Eventually, orange perithecia formed. The disease was reproduced in the greenhouse by dipping oleander cuttings in C. crotalariae spore suspensions of 10³–10³ conidia and ascospores per milliliter and rooting the cuttings in vermiculite under intermittent mist. The cuttings became diseased, and C. crotalariae was reisolated from necrotic tissue. Fungicidal control was tested by immediately dipping inoculated cuttings in several fungicides at a concentration of 1,000 μg/ml a.i. Plant survival was measured by the mean number of days each cutting survived; the trial was terminated after 64 days. Benomyl controlled the disease, with a mean survival time per plant of 61 days. Mancozeb, vinclozolin, and captan reduced disease, with mean survival times of 43–48 days. Etaconazole was ineffective, with a mean survival time not significantly different (P = 0.05) from that of untreated inoculated controls (30 days).