Damage

• The spruce aphid feeds on the black spruce and other spruce tree varieties. It attaches its piercing mouth to the surface of needles and sucks the nutrient-rich sap. The insect's feeding causes the premature loss of older tree needles. Continuous, uncontrolled infestations of the pests can weaken the tree, cause branch death or eventually kill the tree. Ongoing aphid infestations cause a rapid decline in the overall appearance of the black spruce.
  
  

Life Cycle

• From late winter to early spring the aphids appear as tiny green insects congregated on the underside of spruce needles. By late spring, the tree's needles begin to turn yellow from the pests' relentless feeding. A tree often suffers extensive needle loss right before its buds open. The tree's newly growing buds rarely suffer damage from the insects. Aphid eggs appear on the tree's foliage as tiny black, brown or reddish dots. The aphids produce several generations per year and can remain on the tree continuously. The greenish adults appear winged or wingless. Weather temperatures that dip below 15 degrees Fahrenheit will kill the insects.
  
  

Control

• Aphid populations tend to reproduce in greater numbers on nitrogen-fertilized trees, so avoid fertilizing your black spruce to help keep the aphid population in check. Cold weather is your ally in controlling spruce aphids. Fewer of the pests survive following long periods of cool weather or after an early frost. Spray ornamental black spruces in late March or early April using an insecticidal spray that contains bifenthrin, imidacloprid or acephate. Insecticidal soaps can also help gain control of the insects. Injecting imidacloprid into the trunk of a large tree will control the aphids. Pesticide regulations vary by state, so check with your local government for any restrictions on spraying. Always carefully follow pesticide application instructions.
  
  

Black Spruce Requirements

• Maintaining the black spruce's health can help prevent extensive damage from aphids. Plant the black spruce in a site with full sunlight. It grows best in acidic, moist soil and can tolerate nutrient-poor soils. Within its native habitat the black spruce thrives in peat bogs. The tree does not grow well in the southern areas of the United States as its origins are in cold, northern climates. The ornamental cultivar, however, grows well in plant hardiness zones 3 through 7.