Pine needle scale, Chionaspis pinifoliae, is a common insect pest of pines in Missouri. It is most frequently found on Mugo, Scotch (Scots), and Ponderosa pine but will also infest Austrian, red, or white pine and most spruces. Light infestations often go unnoticed and cause little damage. As the population increases, needles become covered with the white-scale insects, which suck juices from the needles. A heavy infestation can cause whole branches to die, or in severe cases, kill the plants.

Symptoms and Diagnosis

The scales are whitish and only 1/10 of an inch long with a yellow spot at one end. As numbers increase, the whole needle may be covered with scale. When pried off, the scales are hollow, and depending on the time of year, they may contain eggs or feeding insects.

Life Cycle

Reddish-colored eggs overwinter beneath the female scales. From May to June, young, called nymphs hatch, and they migrate to new locations by crawling or being blown by the wind. The nymphs settle, begin feeding, and produce a waxy, scale covering. During late July and early August, mating takes place, and eggs are laid under the scale for next year's generation. (In some locations, a second generation may occur in early fall.)

Integrated Pest Management Strategies

1. Prune and maintain vigor. Mild infestations caught early can be controlled by pruning out infested branches. Water and fertilize plants to maintain plant vigor. The use of chemical pesticides will adversely affect populations of beneficial insects that help to control the pest.

2. Properly timed dormant oil spray. A very effective control is to use a dormant oil spray in late March or early April, before new growth begins. The oil coats the scales, preventing oxygen intake so the insects suffocate. Dormant oil sprays are nontoxic to humans, birds, and pets, but must be applied at the right time to be effective and prevent damage to the plant.

3. Properly timed insecticidal sprays. Pine needle scales are very resistant to pesticides when they are protected by their scales. However, they are very vulnerable when they are in the crawler state. In St. Louis, this is around the beginning of May. Examine infested plants with a magnifying glass for the crawlers. In the presence of crawlers, spray with an insecticidal soap, a summer oil spray, acephate (Orthene), or Neem oil. A fall application may also be made around the middle of August if a fall brood of crawlers is evident.

Organic Strategies

Strategy 1 is a strictly organic approach. For an organic approach to Strategy 3, consult the Organic Materials Review Institute (OMRI™) for appropriate insecticidal soap and Neem products.