Aphids on spruce
Large numbers of aphids are being found on the new growth of spruce. Predators such as ladybeetles often are helpful in keeping aphid numbers in low.
Aphids feed on conifers by sucking juices from branches, shoots and needles. Feeding from aphids can cause the foliage to become curled; distorted or affected trees may lose their needles.
Some of the common conifer-feeding aphids produce lots of honeydew, which leads to black sooty mold. On the other hand, there are many insect predators who relish aphids. Often aphid problems take care of themselves – predators such as ladybeetles often knock the population way down fairly rapidly low and aphids will usually disappear after several weeks. The exception is when ants are present – they will protect the aphids from the predators.
Cinara is a group of several species of large brown or black aphids that feed on many conifers. In most cases, when we find these in a Christmas tree field, there are only a few trees with aphids while the rest remain aphid-free. Usually, they are not a problem and disappear after several weeks. A concern with Cinara aphids is that if they are found on the trees in the fall they can remain on harvested trees and may be e a nuisance to consumers once the Christmas tree is set up in the home. Michigan State University Extension recommends scouting your fields and if you find large numbers of aphids, keep monitoring the trees weekly. If you have high populations and the trees will be harvested this year, you may want to apply an insecticide.