The white mold you see forming on your apple tree's trunk is actually a colony of woolly apple aphid insects. Damask holds a Master of Arts in English and creative writing from the University of North Texas. Unlike other species of aphids, the woolly apple aphid infests branches, shots, roots and other woody plant parts. Cut it deep enough so that you remove the fungus inside. The most common disease affecting apple trees is some form of Canker or other. A It’s a very common fungal disease which turns the young shoots of apple trees white. Horticultural oil applied as a dormant spray will control overwinter scales hiding on the apple tree, while vedalia beetles -- which prey on scales -- will naturally reduce their numbers without the use of chemicals. Powdery mildew is rarely a serious disease, and vigorous established apple trees handle an infection without long-term damage. Aphelinus mali -- a predator parasite that preys on the woolly apple aphid -- will control these pests without the use of chemicals. Significance: Death of tree and brittle fracture at base. Q What is apple powdery mildew?. Those that live above ground surround themselves in white waxy filaments that take on a fuzz-covered appearance. University of California The California Backyard Orchard: Apple (Malus Domestica), Missouri Botanical Garden: Powdery Mildew - Outdoors, University of California Integrated Pest Management Program: Woolly Apple Aphid — Eriosoma Lanigerum, Ohio State University Extension: Apple Powdery Mildew, University of California Integrated Pest Management Program: Cottony Cushion Scale, University of California Integrated Pest Management Program: Whiteflies, University of Florida Institute of Food and Agricultural Sciences: Ash Whitefly. Parasitic wasps are natural predators that kill aphid eggs without harming your plants. We bought two-year-old trees, so I am … These aphids cause galls to form at the infestation site, cankers or burs to develop on the branches and stunted growth. My apple trees are now in their 5th year at our house. Carefully cut off the limbs of your tree that are affected with fungi and place them into a disposable bin or container. Small infestations located on the branches can be controlled with horticultural oil or insecticidal soap. Season: Summer to early winter. When planning your home landscape, avoid planting other highly susceptible trees to prevent the reoccurrence and spread of aphids. Infected tree leaves are soon entirely covered with white, fluffy fungus. As they consume the tree’s phloem sap, they secrete honeydew, which leads to sooty mold growth. A It’s a very common fungal disease which turns the young shoots of apple trees white. Apple trees with powdery mildew are usually infected by spores that have blown in and overwintered in the tree. An occasional issue, these aphids target apple trees but do not present a continual severe threat. Powdery mildew is unlike other fungal diseases since it doesn’t require water or moisture for its spores to germinate. This fungus resembles talcum powder, which is where the disease got its name. Vigorous apple trees have a greater potential for fighting off and recovering from woolly apple aphid infestations than poorly cared for or weakened trees. Yellow spotted leaves result from the discoloration and the presence of sooty mold. For severe infestations of aphids that look like white mold on your apple trees, prevent the yellow spotting of leaves and decline of your tree with the application of a chemical control. Amanda Flanigan began writing professionally in 2007. Whiteflies are normally not a problem on certain fruit trees such as apples. However, before treatment can begin, you must identify the exact cause of the growth. Copyright Leaf Group Ltd. // Leaf Group Lifestyle. Grow your apple tree in locations that offer full sun for best growth and fruit production.