The ornamental crabapple or flowering crabapple tree is from the genus Malus hybrids. It is a deciduous tree that is U.S. Department of Agriculture hardy in zones 4 through 8. There are over 35 species and 700 cultivars used in home landscapes today. However, the flowering crabapple has a reputation for disease and pest problems. It is bothered particularly by the Japanese beetle.
The flowering crabapple is best known for its fragrant flowers that bloom for a short period of time in early spring. The crabapple prefers moist, well-drained soil in full sun. It can grow up to 15 to 25 feet. The flower types include single or five petals, semi-double (six to 10 petals), or double (more than 10 petals). They are typically white, pink or red. They form the fruit crabapple, which is different than an apple based on the size. Crabapples are 2 inches or less in diameter. Crabapple trees come in many shapes and sizes based on their unique growth habits.
The flowering crabapple is used in landscapes, parks, schools, and many other areas. They do well planted in fertile, moist soil that supplies a fair amount of organic matter. If not, they will need additional fertilizing, especially in the first year. Once a tree is established, watering is not needed unless drought conditions become a problem. Then crabapples should be watered with 2 to 6 inches of water at least every two to three weeks. Crabapples may be pruned for shaping, and this should be done before early June. After that, the buds for next year's flowers are beginning to form.
The Japanese beetle (popillia japonica) feeds on the leaves and flowers of many ornamentals, including the flowering crabapple. The beetle is a metallic green with copper brown wing covers. The adult has an oval shape and is just over ¼ inch long. They become active in June, with intense activity for a four- to six-week period. They feed in groups and are most active on sunny, warm days.
The adults feed on the upper part of the leaf, chewing out the tissue between the veins, shredding the leaf. The Japanese beetle moves fast and infestation can happen quickly. The beetle also leaves an odor on the damaged leaves that helps attract fellow beetles
Keep in mind that the both the adult and larvae stages can cause damage. The Japanese beetle adults fly from area to area, so controlling one stage may not help control the entire problem. The adult beetles can be removed by hand for small areas of infestation. Natural control includes insecticidal soaps, garlic, hot peppers, or orange peels. Insecticides also can be used including Tempo, and Bayer Advanced Lawn & Garden Multi-Insect Killer. If using insecticides, cover all the leaves and flowers. The application may need to be repeated to prevent re-infestation. Follow all directions when using insecticides.