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Wednesday, May 27, 2015

Black aphids on Chitalpa

Aphids on red Yucca flowers before they Bloom in February
Q. I live 40 miles east of Kingman, AZ and I'm having a bug problem this spring on our chitalpa and ocotillo. There are tiny black insects on every bloom and bud. I've started noticing them on the red-tipped yucca blooms as well. We've had all of these plants for years and they are well established. We would hate to loose them. Should we be concerned about these bugs? 

A. These are black aphids which are common on Chitalpa, its leaves and flowers as well as other plants. They suck plant juice out of the soft tissue of leaves and flower buds and petals, concentrate the sugars taken from the plant and drop it out of their rear as a high sugar, shiny and sticky concentrate.

Aphids and ants working together
 This sugary concentrate attracts ants and can foster the growth of sooty mold. Sooty mold is not sooty canker, a very bad disease of landscape trees. Sooty mold does not infect the plant but just grows along the surface of leaves and stems and is easy to remove.

 Ants herd and protect these aphids from other insects as well as move them around. Controlling the ants helps to control aphids and sooty mold. These insects will not kill the plants but they will affect your plants floral display. Spray these aphids off of your plants with a strong stream of water and control the ants.

Aphids and ants working together on red Yucca after they flowered
Alternatively, spray the flowers and leaves with insecticidal soap, neem oil, canola oil or horticultural oil. If you are still not satisfied with the results, then you can be more aggressive with a conventional insecticide with aphids and ornamental plants listed on the label.

Remember, conventional insecticides can be much more damaging to beneficial insects and honey bees.

Spray in the very early morning hours or at dusk when honeybees are no longer present. If you look at one of your pictures of the flower buds you will see a ladybird beetle immature (larva) feeding on them. It is grey compared to the black aphids.

They are voracious feeders of aphids but there are just too many for this solo beetle larva to handle. Spray them off with a strong stream of water or use insecticidal soap or horticultural oil to kill them.

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