Weeping Higan cherry trees (Prunus subhirtella "Pendula") make handsome additions to home landscapes with their delicate, pinkish-white spring blossoms and long, graceful branches that sweep toward the ground and sway in the breeze. Growing in U.S. Department of Agriculture plant hardiness zones 4 through 8, the weeping cherry is less vulnerable to plant diseases than its relatives. It is still susceptible to various boring insects, however, particularly peachtree borers and American plum borers. Treating your tree with insecticide and following a regular watering routine helps kill off any existing borers while preventing new pest problems.
Inspect your weeping Higan cherry tree for borers every spring or early summer. Borer larvae tunnel into the tree, leaving small holes, wet spots, bleeding sap and a red-orange, sawdust-like substance called frass behind.
Spray your tree with a carbaryl-based insecticide once you confirm borer populations. For optimal pest control, the Colorado State University Extension recommends applying the pesticide before the eggs hatch, which typically occurs from mid-July through mid-August.
Mix about 1 1/2 fluid ounces of carbaryl-based pesticide and 1 gallon of water into a handheld garden sprayer. Following the application instructions and safety precautions on the product's label, thoroughly spray all of the branches and trunks with the solution until the surfaces glisten with moisture. Repeat applications every six weeks until you achieve control.
Help your weeping cherry fend off borer infestations by giving it the proper care. Borers especially enjoy attacking drought-stressed trees growing in dry soils, so water your tree deeply once a week during extended periods of hot, dry weather. Use a soaker hose and allow the water to run until it moistens the top 6 to 12 inches of soil.
Apply a 2- to 4-inch layer of organic mulch around the tree. Mulch helps keep the soil moist while preventing bark injury, which can open your cherry tree up to borers.