Q: I just spotted aphids on my roses. Are my plants goners? What should I do?

A: The major rose pests in Colorado are aphids, spider mites, thrips and powdery mildew. To control aphids, begin with the least intrusive and easiest to apply remedy, and then move up the “Big Bad Ladder of Destruction”. Get the garden hose and apply a strong jet of water to the infected areas. Aphids are soft bodied insects; the jet of water removes them from the plant. Reapply as needed.

If they continue to be a problem, consider biological controls like the dreaded lady beetle. Lady beetles love to munch all those tasty aphids. Lady beetles can be found at local garden centers. Apply to the rose, ring the dinner bell and let the lady beetles work. Keep in mind these are live insects, and after application, may decide to see what’s for dinner in your neighbor’s yard.

If you decide to use an insecticide, understand it may not only kill aphids but also beneficial insects in the sprayed area. Read and follow all directions before use. Neem oil is an organic insecticide and might be a good place to begin. The active ingredient in Neem is azadirachtin, which acts as a growth regulator that interrupts the insect growth cycle causing larval and pupal death. It provides effective control for whiteflies, mealybugs, thrips, aphids, leaf miners and others. It can be toxic to bees if applied while bees are active. See CSU Extension Fact sheet #5.511, “Aphids on Shade Trees and Ornamentals” for more information.

Q: All my trees are set up on a drip irrigation system. As my trees mature what changes should I make?

A: A drip irrigation system is a great solution—not only is it more efficient than other systems, in regards to water loss due to runoff, wind and evaporation, but it can be operated during windy periods. As your trees mature you will have to increase the amount of water applied to each tree. This means either extending the watering times, adding more emitters or changing emitters to units with higher flow rates. A combination of all three should cover your tree’s needs.

Keep in mind as the tree grows the root system is expanding. Because of this, you will need to move the emitters further away from the root ball. If your tree gets taller than 25 feet at maturity its root system may outgrow the drip system. Consider converting to soaker hose irrigation. To extend the efficiency of any irrigation system, think about mulching the area around your trees. For more information see Fact sheet #4.702, “Drip Irrigation for Home Gardens”.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  August 5, 2008