Periconia Blight of Hevea

Abstract

In December, 1943, an unknown disease characterized by a severe leaf spotting was found in a nursery of Hevea Spruceana at Turrialba, Costa Rica. Six weeks later, following a prolonged rainy period, this disease had reached epiphytotic proportions in the spruceana nursery where it was causing leaf, petiole, and twig blight, and also was producing minor damage in a nearby nursery of Hevea brasiliensis seedlings. In addition to Turrialba (elevation 2000 ft.) the disease was noted near Gualipes, Costa Rica (elevation 600 ft.). An earlier observation of the same disease was made by W. J. Martin on H. brasiliensis at El Palmar, Tezonapa, Mexico, but no collections were made. The leaf spots are circular to oval, at times somewhat irregular or elongated along the veins, but not vein limited, appearing much the same on both surfaces. Primary lesions vary in diameter from two to ten millimeters, but frequently coalesce, particularly on younger leaves, to involve an entire leaf and may bring about premature abscission. The spots are brown at first, becoming ashen at the center with a brown border, and on mature leaves (FIG. 1) they are often ringed by a chlorotic halo. Necrotic areas split irregularly and may even fall away in part. Petiole lesions are common and, when severe, cause leaf abrasions or petiole breakage. Petiole lesions or leaf spots sometimes spread down to the leaf axils and cause sunken twig cankers or die-back of young soft twigs (FIG. 2). This disease has been found on Hevea brasiliensis, H. Spruceana, H. guianensis, H. Benthamiana, and on hybrids of H. brasiliensis x Spruceana. H. Spruceana clones selected for resistance to South American leaf blight (Dothidella Ulei P. Henn.) are readily attacked. H. brasiliensis clones, highly resistant to D. Ulei, have been heavily infected when growing under a thin overstory of