A rose problem is almost always a reflection of the plant’s environment. A proper site location, correct watering habits, adequate soil, drainage, spacing and maintenance will help from the start. A strong healthy plant is the first line of defense against any rose problem. Grown in proper conditions, the rose will not be stressed. Follow label instructions on all pesticides or fungicides to avoid plant damage.
Masses of insects on the buds and leaves:
Aphids – green, red, black soft insects,1/8” or smaller, found clustered mostly on new growth or flower buds. Most organic and synthetic insecticidal sprays including insecticidal soap are effective. Or simply hose off the insects while watering
Blooms are shredded, discolored, or buds are distorted:
Thrips – light brown insects about 1/8” long. Squeeze an open bloom and watch the inside of the petals for movement. Apply insecticides – neem oil, pyrethrin’s, insecticidal soap, or systemic when you see the symptoms.
Leaves appear speckled on the surface, underside has small red specks with webbing:
Spider mites – microscopic in size, but visible to the naked eye. Hot weather is the prime season for spider mite activity. Apply insecticidal soap, neem oil or miticides.
Leaves eaten leaving a skeletal structure. Unopened flower buds chewed:
Beetles – most notorious is the Japanese beetle, metallic brown with green head. Sawfly looks like a caterpillar but wasp larva and eats leaves. Apply insecticide Eight or pyrethrin. Physically removing or shaking beetles off the plant into a soapy filled bucket is an alternative.
Tumor-like growths on canes, roots, or at bud union:
Gall – a bacterial problem. Prune away affected section. Sterilize pruning tools with bleach or alcohol to prevent bacteria from spreading.
Leaves are distorted, a white powdery fuzz appears on buds and leaf tops and bottom:
Powdery Mildew – a fungal disease fostered by cool nights, warm days, and high humidity. Apply fungicides such as copper fungicide, rose Rx, insecticidal soap. Make sure plants have good air circulation and ample sunlight. Mildew is more aesthetic than harmful.
Dark black round spots or blotching on the leaves, pinpoint to quarter size. Half of leaf yellows or leaf drops completely:
Black Spot and Anthracnose – both are favored by rainy weather or improper watering. Apply neem oil, copper fungicide, rose Rx on the underside of leaf and top. When watering, keep foliage dry. Neither disease will kill the plant but can weaken it.
American Rose Society www.rose.org can provide additional information.
