Double Knockout Rose Problems

Characteristics

• The Double Knockout rose grows on a compact bush averaging 3 to 4 feet tall and wide. The bright-pink or crimson flowers measure about 3 to 3-½ inches across and grow in 1- to 5-flower clusters with up to 25 double-petaled blooms per flowering branch. The deep, mossy-green foliage has blue and maroon highlights and a maroon underside. These low-maintenance roses are drought tolerant and hardy from U.S. Department of Agriculture plant hardiness zones 4 through 10.

Aphids

• Tiny pear-shaped aphids suck large quantities of sap from the plants they infest, stunting and distorting growth. These slow-moving insects come in a variety of colors including green, black, brown, red or pink. Aphids excrete honeydew which is a sticky substance that attracts a sooty mold that grows on plant surfaces and block photosynthesis. Non-chemical controls of aphids on double knockout roses includes removing the aphids with a steady stream of water or introducing natural predators like lady beetles and aphis lions to feed on the aphids.

Thrips

• Thrips are small, cigar-shaped insects with pale-yellow bodies and fringed wings. Although thrips are attracted to plants by the pollen, they feed mainly on plant tissue, extracting plant fluids with rasping/sucking mouthparts. Thrips also feed on flowers, turning the petals brown. More important than the damage thrips do through feeding is their potential to transmit disease. Predatory mites, pirate bugs and lacewings feed on thrips, providing nonchemical control.

Japanese Beetles

• The adult Japanese beetle measure about 1/3 to ½ inch long and with shiny, metallic-green or copper wing covers. They feed by chewing on the Double Knockout rose's leaves and flowers. Manually removing Japanese beetles from your roses effectively reduces the population without resorting to chemical insecticides.

Rose Rosette Virus

• Double Knockout roses posses high resistance to many diseases plaguing most rose varieties. However, rose rosette virus is a growing concern for Double Knockout rose owners because the plant is not resistant, and the disease is fatal. New shoots rapidly elongate creating a witches' broom clustering of small branches with small, distorted red leaves. Flowers are distorted and abnormally colored with fewer petals than normal. Stems may also develop and excessive amount of red or green thorns. At this time, nothing is available to effectively control rose rosette virus.