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Giant Conifer Aphids and Denver Trees


Brown, pear-shaped, and 2 to 5mm long, Giant conifer aphids or Cinara form colonies on stems and branches of conifers. Often found in large groups, they feed on the sap in needles, branches, trunks and roots. Their life cycle includes several generations per year. Their eggs hatch in the spring and molt through several stages, becoming larger each time. Females give birth to live young with and exception with the last summer generation when overwintering eggs are laid on needles or bark.  

Giant conifer aphids can cause damage with heavy infestations on Denver conifer trees which can cause yellowing of the foliage and even reduce tree growth. The best evidence of an aphid population is the presence of honeydew. You can also tell from the damage on the trees – yellow patches on the needles are the first sign of an aphid feeding.
Natural enemies are ladybeetles, lacewings, syrphid flies, or parasitic wasps and can usually bring an aphid population under control. However, direct control may become a necessity and the population may need to be controlled with insecticides. With the giant conifer aphid populations building up by early spring, application timing is critical. When aphids are sighted there are several options for controlling them:
  • High-pressure water spray to dislodge them. May need to be repeated throughout the season
  • A spray of 2 percent solution of mild dishwashing soap in water is helpful for low populations of aphids
  • When your tree is 25 feet tall or more, some chemical options are available. Systematic insecticides are best and should be considered if the tree is being significantly attacked.
There are many different types of giant conifer aphids and can attack certain conifer trees in the pine and cypress families such as Ponderosa, Juniper, or Austrian Pine. Now that cooler seasons are upon us, it’s important to make sure the problem is taken care of before the overwintering of their eggs. Contact American Arbor Care, your Denver tree care specialists today to find out how we can help with your giant conifer aphid problem. 
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