Sap-Sucking Insects, Gall Formers and Mites

Hosts: Hardwoods and conifers, particularly ponderosa pine and spruce.

Figure 57. Figure 57. Cinara aphids on pine host.

Symptoms/Signs:  The best evidence of infestation is the insects themselves or shiny leaves from the honeydew. Honeydew is a clear, sugary, sticky liquid that aphids excrete as they feed. It accumulates on the foliage, twigs, trunk and ground. Honeydew attracts ants, and often the presence of ants on a tree may indicate that aphids are there. It is also a good growth medium for sooty mold, which grow on affected portions of the tree. Aphids are small soft-bodied gregarious insects. Adults may be winged or wingless. Nymphs are wingless. They vary in color by species, but may be nearly colorless to green to black.

Figure 58. Figure 58. Eggs of aphids on pine needle.

Biology:  Typically aphids produce several generations per year, most are parthenogenetic. The last generation is usually sexual, and then winter is spent in the egg stage. Different aphids feed on different parts of their hosts, including the foliage, twigs, trunk, and roots. All aphids have piercing mouthparts that they use to feed on sap from their host plants.

Figure 59. Figure 59. Aphid damage to conifer host.

Effects:  Feeding can result in formation of small necrotic spots. Heavy feeding by some species can cause early leaf drop, yellowing of foliage, and reduced growth. In general, these insects are not considered economically important in forest situations. In urban areas, the honeydew can accumulate on walkways and vehicles and attract the attention of the public.

Similar Insects and Diseases:  Damage caused by aphids may resemble that caused by needle midges, other sucking insects, or needle diseases.

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