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Perhaps the most common insects in our gardens are aphids. I have a large Norway maple in my front yard that is infested every year. I have also seen aphids on my columbines, lupines, spireas and chrysanthemums. Aphids are one of the most serious pests of roses. Last summer, aphids were especially common in Larimer County. This year, some people have already reported seeing aphids on their roses during midwinter. If this is any indication, 2000 could be another banner year for these pesky insects.
Aphids are soft bodied insects that feed on plant juices. Many species occur in colonies of 10 - 80 individuals on tender shoots, leaves and stems. They have mouthparts made up of specialized tubes that resemble a drinking straw, which they insert into plant tissue. Some aphids have wings and can fly short distances. Others lack wings and depend on air currents or ants to move them to new locations.
Aphids feeding on shoots and foliage can kill new growth. Other aphids inject salivary fluids into plants to partially digest the juices before taking them into their bodies. Sometimes these fluids are toxic and can kill all or part of the plant. Still, other aphids produce galls. The females inject a growth altering substance into the plant tissue as they lay eggs and an unattractive growth, called a gall, forms in which young insects develop. One of the most common galls in our area is the cone shaped gall caused by Cooley spruce gall aphid on spruce.
Aphids also produce a sticky material called honeydew. Park your car underneath an aphid-infested tree and it will be covered with tiny droplets of honeydew. This is how I know my Norway maple has aphids. Every spring, just as the leaves develop, droplets of honeydew appear on the windshield and body of my truck. Honeydew is a perfect medium for sooty molds. These dark colored fungi grow on tree bark, foliage, even your car if you don't wash off the honeydew. Some ants eat honeydew and have developed a beneficial relationship with aphids. The aphids provide ants with food while the ants protect the aphids from predators and move them around on their host plants.
Infestations can be recognized by drying of young shoots and leaves or leaf curling. Many, but not all galls, are caused by aphids. The aphids themselves are tiny, usually green or brown in color with soft bodies. Sometimes the presence of ants on your plants may be a hint that aphids are present. The colorful orange and black spotted ladybird beetles, so common in gardens, feed on aphids. If you see two or three ladybird beetles or larvae, which resemble tiny crabs in your garden, they are working to keep the aphid population in check.
Another easy and safe way to control aphids is with a stream of water from your garden hose. This dislodges the insects and washes them away but must be repeated several times. Detergents, or insecticidal soaps diluted to a 1 or 2 % concentration, will also control aphids and an early spring application of a dormant oil will effectively treat aphids originating from eggs that have passed the winter. Effective contact insecticides for most aphids include malathion, diazinon and Dursban. Sevin or carbaryl is effective against woolly aphids found on evergreens and Orthene or acephate, an insecticide with systemic properties, is also effective against many aphids. When using insecticides always read and follow the directions on the label.
For more information on aphids and their control, see Fact
Sheet #5.511 - Aphids on shade trees and ornamentals. You may
also call PlantTalk Colorado at 1-888-666-3063 and request message #1402
on aphids or view
the message text here.
Q: What varieties of tomatoes should I plant in my home garden?
A: Many varieties of tomatoes are available that are well suited to the northern Colorado Front Range. Early Girl is a popular variety because it can produce ripe fruits in early July. This is a fairly small tomato but has a good flavor. Roma is a pear-shaped tomato, produces large numbers of fruits and is an excellent choice for home canning. Big Beef is a large, juicy and good tasting tomato that requires a longer period to mature. Other good choices include Big Boy, Fantastic and Celebrity.
Q. There is what seems to be a “walking” reddish brown dust around the windows on the south side of my house. When mashed it leaves a rusty stain on things. Is there anything I can do to prevent this?
A: These are clover mites which move out of the house in the spring and back in the fall. They are harmless in the home but a nuisance. A foliage-free area between the grass and the foundation of your house will help prevent them from entering. Outside they feed on grass and plants in sunny locations. Many pesticides can be used to create a barrier against them around the south and west sides of your home. Infested areas of the lawn can also be spot treated with these insecticides. Read and follow direction on the insecticide label.
Q: I am considering purchasing zoysia grass for my lawn in Fort Collins. Is this a good choice?
A: Zoysia grass is not recommended for home lawns in this area. It is subject to winter kill, is slow to establish (2 - 3 years), and stays brown 2 to 3 months longer than blue grass. It is subject to rust and fairy ring disease and does not grow well in shady areas.
Q: I just pruned my ash tree. Should I apply a wound dressing?
A: Wound dressings are no longer recommended. Covering the pruning wound interferes with the tree’s ability to form callus tissue. It is better to make a clean cut just outside the branch “collar” (the natural swelling at the branch base) and allow the wound to dry.
Q: I planted vegetable seeds inside to transplant in my garden later. They came up but fell over and died before they got very big. What happened?
A: What you describe sounds like “damping-off,” a disease caused by fungi living in the soil. Make sure the containers you plant in are cleaned with a dilute bleach solution before using. Fill the containers with a sterile, well drained potting medium instead of outside garden soil. A good mix to try is one-third peat, perlite, and sterile potting soil. After planting your seeds, keep the medium moist without saturating it.
Arbor Day is April 21st. Plant a tree! Early spring is an excellent time to plant or transplant trees and shrubs. The Larimer County Office of the Colorado State University Cooperative Extension has fact sheets on selection and planting of trees and shrubs for this area. Information is also available on trees and shrubs that will grow successfully in mountain communities.
Plant beets, carrots, lettuce, onion sets, parsnips, peas, early potatoes, radishes, spinach and turnips in the garden. Harden off seedlings of cabbage, broccoli and cauliflower before planting in the garden. Put the plants outside in a shady, wind protected area for an increased amount of time each day for about seven to 10 days. This will acclimate your plants to our intense sun and cool nights.
Divide mid-to late-summer and fall flowering perennials such as chrysanthemums and asters in early spring before growth begins. Using a spade or shovel, dig up the entire plant. Remove soil from the roots and cut apart the healthiest portions of the root system using a sharp knife. Throw away the diseased and dead portions of the plant and replant the divided perennials as soon as possible. Give away extra the plants to your friends.
Dormant oil spray applied in early spring before plants leaf out can be an important tool to manage insects and mites on fruit trees and other woody plants. Spray oils are exceptionally safe to humans and animals. Do not apply dormant oils when the air temperature is below freezing or if plant tissues are wet or rain is likely.
The author has received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.
Fact Sheets are available at the Larimer County Extension Office, 1525 Blue Spruce Drive, Fort Collins, Colorado, telephone (970) 498-6000, or contact us by e-mail at larimer@coop.ext.colostate.edu
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