Issue: June 22, 1996

Puckered areas on roses

Question: The leaves on my roses are developing puckered areas. I have noticed that these areas tend to be off-color, not like the rest of the leaf. Do they have a disease?

Answer: You may be seeing the early stages of powdery mildew infection. By the time you read this, it will probably have progressed to the stage where the white, powdery spores are apparent. Powdery mildew can cause leaf deformation, leaf drop, and flower deformation. It is a common disease favored by high humidity and temperatures in the sixties at night. We have now entered the season with the proper night temperatures, but many people wonder how we have enough humidity in a drought year. It doesn't take extremely high humidity. Evening or night watering of flower beds and lawns is enough to provide the necessary humidity. The plants themselves create localized high humidity as they transpire water from the leaves and trap that moisture among the leaves.

Pruning to open the plant and allow better air movement through the plant canopy will help reduce the powdery mildew problem but will probably not eliminate it. Reduced frequency of irrigation and irrigating only in early morning will also help. There are some fungicides intended for management of powdery mildew on roses and other plants. These chemicals will not cure powdery mildew but can arrest its spread through the parts of the plant which are not already infected. If you choose to use one of these, be sure to follow the directions carefully.

According to Dr. Natalie Goldberg, NMSU Extension Plant Pathologist, there are several Fungicides available to control powdery mildew on roses. For those who want to use organic materials, sulfur and bordeaux mixture will help to reduce disease but not cure it. Daconil and Triforine are the most readily available of the synthetic fungicides. She emphasizes that even the strongest of fungicides can't eliminate the disease once it starts. The fungicides are useful to stop the spread of the fungus but cannot cure what has already attacked the plant.

Fending off bees and ants from hummingbird feeders

Question: Ants and bees are chasing the hummingbirds from my hummingbird feeder. What can I do to get rid of these pests?

Answer: Ants can be defeated with a little work. Coat the wire or string by which the feeder hangs with Tree Tanglefoot (TM) or another sticky substance. The ants will be unable to reach the hummingbird feeder until dust or enough dead ant bodies provide a bridge across the sticky substance. If you periodically wipe the dead ants and dust off and reapply the sticky material, you can discourage the ants. They will usually give up after a while and go look for an easier source of food. Be careful not to apply the sticky material where it can get on the feathers or feet of the hummingbirds. Just apply it where it will discourage the ants.

Bees may be managed in a couple of ways. Let the hummingbird feeder go dry for a week or so and the bees will leave it. Another trick is to move the hummingbird feeder periodically. Bees do an interesting dance in the hive to tell other bees the direction and distance to a source of nectar. If you move the hummingbird feeder, the information in the dance will be inaccurate until another bee finds it and tells the hive. Then just move it again. The hummingbirds find the nectar by sight; they are attracted to the red color of the feeder.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!