How to distinguish the harmful symptoms of downy mildew and gray mold of roses?

Downy mildew mainly harms leaves, shoots, shoots and flower organs, especially young leaves. At the early stage of the disease, the diseased leaves showed irregular light green stripes, yellow-brown and deep purple after expansion, and finally grayish brown with dark edge color, which gradually expanded and spread to healthy tissues. In wet weather, a sparse gray-white downy mildew layer can be seen on the back of the diseased leaves. When the new shoots and flower organs are infected, the lesions are similar to those on the diseased leaves, but the lesions on the new shoots are slightly depressed. In severe cases, leaves atrophy and fall off, and new shoots rot and die.

Gray mold of rose also mainly harms the flowers, leaves and tender stems of rose. When the bud comes on, it leans to one side, and the lesion is gray-black and can spread to the whole bud. Finally, the diseased buds cannot open, turn brown and die. When the petals are infected, small waterlogging spots appear in the early stage, and the color of the spots varies with varieties. White varieties form reddish-brown spots, and pink and red varieties form light gray spots. When it occurs at the edge and tip of leaves, it is a flooded light brown spot at first, which sinks slightly, then turns brown and shrinks, and the tender diseased leaves droop. Later, the lesion gradually expanded, and a number of lesions were connected to form irregular serious spots, and the color gradually turned brown, rotted, wilted and withered. When the tender branches are infected, dark brown concave spots are formed in the middle of the stem nodes, and in severe cases, the upper branches wither and die. In warm and humid environment, the surface of diseased tissues is densely covered with botrytis cinerea, which is the conidiophore and conidia of pathogenic bacteria.