The pine needle scale has another common name: "the white malady". This is due to the fact that it was historically a considerable native pest of pine and spruce species and is a serious pest of ornamental pines in the United States. Reddish colored eggs overwinter underneath the armored scale cover (test) of the female insect. Each female pine needle scale may be capable of laying up to 100 eggs. Adult females are wingless, but adult male pine needle scales are tiny, winged insects capable of flying short distances. Adult female scale covers are mostly white with some yellow, oyster-shell shaped, and elongated. The body of the female (beneath the test) is yellow; red or purple when she is gravid (with eggs). Male covers are similar but with 3 longitudinal ridges. Egg hatch occurs approximately in May and June and red-colored nymphs (immatures; crawlers) emerge from the scale coverings of the females and find a new location on the host plant needles to settle and begin feeding. The crawler stage may also be blown to new host plants on the wind. Depending upon geographic location, one or two generations of pine needle scales occur per year. If a second generation is present, second generation crawlers are present by late July through September. (Two generations per year occur in Massachusetts. More northerly locations may have a single generation per year.) In some populations of this insect on certain hosts in certain areas, parthenogenesis (asexual reproduction) has been observed. The pine needle scale is also very similar to the "pine scale" or Chionaspis heterophyllae, which is so similar it cannot be separated using field identification characteristics, and was once thought to be the same species. It is also possible that this is a species complex of two "sibling species" (Johnson and Lyon, 1991; Miller and Davidson, 2005). The pine needle scale is an example of a species that it native to the United States that has become invasive elsewhere (ex. England and Germany; Miller and Davidson, 2005).
A very serious pest of the needles of ornamental pines. Trees growing in ornamental nurseries, Christmas tree plantations, ornamental plantings, and dusty areas may be more likely to be attacked by this insect than those growing in natural forest stands. Heavy damage can lead to needle drop giving the plant a spindly appearance. Light infestations may go unnoticed and typically do not cause considerable damage. As a population increases, this scale insect feeds with piercing-sucking mouthparts to remove host plant fluids from the needles, causing them to eventually turn yellowish in color and possibly brown. Twigs and entire branches may eventually be killed. Sparse, off-color foliage or entire tree mortality can result. Lower branches typically die first.
Visually inspect ornamental pines at least twice a season for this insect. Elongated, oystershell shaped, adult scales may appear white and coating host plant needles. Monitor lower branches of host plants first, particularly those growing in ornamental settings, nursery production, or near dusty roads or similar locations. Look for branches showing signs of needle yellowing or browning and inspect the needles.
Some studies have shown a variation in survival rates and pine needle scale fecundity across four varieties of Scotch pine, suggesting the possibility of host plant resistance (Miller and Davidson, 2005). Eliason and McCulloch (1997) found that the abundance and fecundity on different varieties of Pinus sylvestris was higher on 'Riga' and 'Pike Lake Improved' compared to the relatively lower 'Belgium' or 'Land O'Pine'. Prune out and destroy heavily infested branches when possible. Maintaining host plant health with help increase the chances of survival and success, and a species and structurally diverse planting may also help attract the important natural enemies of this insect.
A multitude of natural enemies of the pine needle scale are known. These include but are not limited to those in the genera: Ablerus, Aphytis, Coccobius, Coccophagus, and Encarsia (parasitic wasps), Leucopis (predatory flies), and Chilocorus, Harmonia, and Scymnus (predatory lady beetles). Additional natural enemies are also reported (ScaleNet; CABI Compendium). The natural enemies at work in pine needle scale populations are extremely important in lowering pest populations of this insect. If choosing chemical management options, choose those that are reduced risk and have the lowest potential of unintended impacts on natural enemies.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (NL)
Bifenthrin (NL)
Buprofezin (NL)
Carbaryl (L)
Chlorpyrifos (N)
Clothianidin (NL)
Cyantraniliprole (NL)
Cyfluthrin (NL)
Dinotefuran (NL)
Emamectin benzoate (L)
Gamma-cyhalothrin (L)
Horticultural oil (L)
Imidacloprid (L)
Insecticidal soap (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Neem oil (NL)
Pyrethrin + sulfur (NL)
Pyriproxyfen (L)
Spinetoram + sulfoxaflor (N)
When used in a nursery setting, chlorpyrifos is for quarantine use only.
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (soil drench).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
