Forests

Seedlings sometimes fail to sprout or die soon after. Seeds may rot before germinating, shoots may decay before they emerge, or stems of seedlings may be attacked near the soil line, causing young plants to collapse. These diseases are collectively called “damping off,” likely caused by a number of soil…

Downy mildews, including Peronospora and Plasmopara spp., are pathogenic water molds (oomycetes) that primarily damage foliage. Hosts include cane berries, roses, various herbaceous ornamentals, and many fruit, grain, and vegetable crops. CategoryFungiSigns/SymptomsDowny mildew causes pale green to…

 Fire blight is a common and frequently destructive disease of pome fruit trees and related plants.  The disease can destroy limbs and even entire shrubs or trees. Caused by the bacterium Erwinia amylovora. Pear (Pyrus species) and quince (Cydonia) are extremely susceptible.  Apple, crabapple …

Fungus.  Various host-specific forms of Fusarium oxysporum can kill infected plants. Hosts include asparagus, bean, cabbage, cantaloupe, pea, tomato, and watermelon. There are many varieties of host plants with resistance to Fusarium wilt.Like verticillium, causes leaf…

Late blight of potato was responsible for the Irish potato famine of the late 1840s. Late blight is caused by the oomycete Phytophthora infestans. Oomycetes are fungus-like organisms also called water molds, but they are not true fungi. CategoryFungiSigns/SymptomsLesions appear as small dark green water…

 Fungal disease that affects the blossoms, fruit, leaves, and shoots of peaches, ornamental flowering peaches, and nectarines. One of the most common disease problems for backyard gardeners growing these trees. When severe, the disease can reduce fruit production substantially. The loss of leaves and…

 Powdery mildew is a common disease on many types of plants and is prevalent in many areas of California. Infection occurs when fungus contacts a suitable host and environmental conditions are favorable. Infections spread as spores produced in these white patches move by wind and splashing rain to other…

Grows on plants and other surfaces covered with honeydew, a sticky substance created by some certain insects. Doesn’t infect plants, but the mold can indirectly do damage by coating leaves to the point that sunlight can’t reach the leaf surface. Without adequate sunlight, the plant cannot effectively…

Verticillium Wilt, one of the most widespread and destructive soil-borne diseases of plants, attacks many woody and herbaceous species throughout the world. The causal fungus, verticillium dahliae, infects susceptible plants through the roots and invades and plugs the water conducting tissues. Verticlllium…

Virus transmitted by aphids. After feeding on an infected plant, aphids are only able to transmit this virus for very short periods of time (minutes to a few hours). In general, spread of potyviruses in the field occurs when aphid activity is high and is often very rapid and localized. …