Abstract

The species of Omphalia which constitute the subject of this paper are now considered (2) to be the cause of decline disease in the date palm, Phoenix dactylifera L. This malady was first detected in 1921 near Indio, California. Since that time the disease has become well distributed (4) throughout the date-growing region of the Indio district, but it is unknown beyond the boundaries of Riverside County. All underground parts of the palm (3) may be attacked by these fungi, but the principal injury results from the destruction of roots. Secondary symptoms (1) appear subsequently and include the premature death of leaves, retardation in the rate of terminal growth, and reduction in the size of leaves and fruitstalks. The fruit from severely affected palms is nearly worthless. Among the micro6rganisms associated with diseased palms were certain white, sterile fungi with clamp connections at the septa. The first of these cultures was isolated in 1931 by L. J. Klotz, who obtained slight evidences of infection from the inoculation of seedling date palms. Little significance was placed on these results at that time. Later work by the author (2) revealed the pathogenic nature of Klotz's culture, together with that of numerous isolates of similar character from other diseased palms. Since no fruiting bodies of these basidiomycetous fungi were found about date palms affected with decline disease, effort was directed toward inducing sporulation artificially. A group of imperfect toadstools developed in the greenhouse on a wooden pot label (FIG. 3, C). A moldy leaf base from a diseased palm had been buried in soil near the base of this marker. Mycelium which

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