In the summer of 1944 a disease of apricots in Utah County, Utah, was brought to the attention of the staff of the Utah Agricultural Experiment Station. This disease was characterized by a scorched appearance of the edges of the leaves and therefore was called apricot scorch. They typical symptoms of apricot scorch are a scorching and curling of the margins of the leaves. The scorched area usually turns a characteristic reddish-brown color, but sometimes is quite light brown or gray. The injury starts at the margins of the leaves and works inward in waves first scorching the marginal portion of the leaves, then, after a period during which no injury takes place, scorching the out edges of the formerly uninjured part of the leaves. At the edge of each wave of injury a darker brown line is usually left in the scorched portion of the leaf. Apparently health leaves from an apricot tree which shows some scorching will often develop a marginal necrosis if they are picked and are stored for 48 hours in a closed Mason jar. Apricot leaves form orchards in areas where scorch is not common do not exhibit this marginal necrosis when they are given the same treatment. A tree which has been slightly scorched may later appear to a casual inspection to have never been scorched. This is because the dead areas at the margins of leaves may eventually drop off, leaving the tree with a completely green appearance but with the leaf margins gone. The Chinses type of apricot is apparently more susceptible to apricot scorch than is the Moorpark type. In the work reported in this paper, however, no attempt was made to classify samples or results on a varietal basis
