EASTERN SPRUCE GALL APHID
(Chermes abietis). Very common in home
plantings of Norway spruce, also on white, black, and Engelmann's
spruce. Greenish aphids winter around the bud scales and lay eggs on
twigs in spring. The nymphs feed on new growth causing leaf bases to
enlarge into bulb-like hollows, up to 50 of these cells being joined together
to form a pineapple-shaped gall at the base of a twig and usually 2 or 3
galls together on a branch. New galls, up to an inch long, are green with
the closed mouth of each cell marked with a red or purple line and each
containing a dozen or so aphids. The cells open in midsummer (early
August in New Jersey), releasing the aphids to lay eggs on the needles.
These hatch in a few days into the overwintering nymphs. The galls
turn brown after opening, and branches frequently die back.
Control. On small trees cut out the galls before they open if it is possible to do this without too much disfigurement. Spray in spring just
before new growth starts with a miscible oil, 1 to 30 dilution, making sure
the temperature will stay above 45 °F. until the spray has dried, or with
nicotine sulfate and soap, or with lindane.
COOLEY SPRUCE GALL APHID
{Chermes cooleyi). This species causes large
terminal galls, 1 to 2 inches long, on Colorado blue spruce and also
on Sitka and Engelmann's spruce. Aphids winter near terminal buds and
lay eggs in spring, the nymphs producing the gall which is an enlargement of the stem together with thickening of the needles. The green
changes to straw color after the cells open in July. The aphids released
then acquire wings and migrate to Douglas-fir, laying eggs in nests of
white wax, the nymphs remaining on fir needles until spring, when
eggs are laid there. From that generation winged individuals migrate
back to spruce, the complete life cycle taking 2 years.
Control. Unless trees are too large it is easy to cut off terminal galls
before they open. Oil spraying should be done with caution, for it takes
bloom off the needles. Spraying with lindane or nicotine is preferable.
ELM COCKSCOMB GALL APHID
(Colopha ulmicola). Green elevations with
red tips, looking like cocks' combs, are filled with green or brown
aphids which drip honeydew from the leaves onto walks and parked
automobiles. There is no practical control.
GOLDENGLOW APHID
(Macrosiphum rudbeckiae). Bright red lice with long
legs stand out from goldenglow stems, crowd between larkspur
buds, and cause delphinium leaves to cup downward.
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Types of Garden Enemies
