Adult pine bark adelgids are typically dark purple or yellow and range from 1-2mm long. One of the most noticeable characteristics of the pine bark adelgid is the white, woolly, or “cottony” material the pest secretes for protection. This cottony mass covers their bodies, giving them a unique appearance.
Nymphs resemble but are smaller than adults. At first the nymphs are naked and yellow, but the newly hatched nymphs soon darken and begin to secrete white, fluffy threads.
When infesting their host trees, pine bark adelgids tend to settle on the undersides of branches, particularly near the bases of needles. As populations of adelgids increase, the woolly masses can coalesce and cover large areas of the host tree. In severe infestations, these masses can merge, giving the appearance of a whitewashed coating on the trunk and branches.
Life Cycle
The life cycle of the pine bark adelgid begins with adult females laying eggs (up to approximately 24) in late spring or early summer. These eggs hatch into nymphs. The nymphs crawl to the base of needles on pine trees, establishing themselves and feeding on the plant. As the nymphs feed and grow, the pests molt several times, shedding their exoskeletons and developing into wingless and winged adults.
Wingless adults remain on the same tree and reproduce, while winged adults disperse and find new host trees to infest. As the adults age, the pests lay their eggs on the bark of pines or alternate hosts, such as blue spruce. The eggs then hatch into nymphs, repeating the life cycle
Damage & Symptoms
Severe infestations of pine bark adelgid on white pine trees can cause significant damage and symptoms. These tiny insect pests feed on the plant’s sap, which can weaken and eventually kill the tree if left untreated.
One of the most noticeable symptoms of a pine bark adelgid infestation is the drooping, yellowing, and dying of shoot tips. This occurs because the adelgids suck the nutrients from the tree’s needles, depriving them of the necessary resources to produce healthy new growth. As a result, the affected shoots become weak and eventually die off.
Another telltale sign of an infestation is the presence of migratory females on the needles. These migrant females are tiny, whitish or light gray insects that can be observed on the undersides of the needles. These insects often leave behind waxy strands or woolly material.
If left untreated, severe outbreaks of pine bark adelgid can lead to the mortality of affected trees. The incessant feeding by these insects weakens the tree’s overall health, making the tree more susceptible to other pests and diseases. Ultimately, the combination of damage caused by the adelgids and the tree’s compromised condition can result in the death of new shoots and even the entire tree.
Host Plants
The pine bark adelgid is primarily found on white pine trees (Pinus strobus). However, the insect can also infest other pine species, such as the following:
- Scots pine (Pinus sylvestris)
- Austrian pine (Pinus nigra)
- Red spruce (Picea rubens)
- Black spruce (Picea mariana)