Kansas State University

–by Dr. Raymond Cloyd

The pine tortoise scale, Toumeyella parvicornis, is a major insect pest of pine trees grown as Christmas trees. Pine tortoise scale feeds on many different types of pines, including Scots, Austrian, and red. Females are 1/6 to 1/4 inches (4.2 to 6.3 mm) in diameter, hemispherical, and red to brown, with dark-brown to black markings (Figure 1).

Fig 1. Pine Tortoise Scale on branch of pine tree (Auth–Raymond Cloyd, KSU)

Pine tortoise scales overwinter as fertilized females on branches (Figure 2).

Fig 2. Pine tortoise scale females on the twig of a pine tree (Auth–Raymond Cloyd, KSU)

Eggs are laid underneath the body of adult females. Females can produce up to 500 eggs within a generation. Eggs hatch and red nymphs (crawlers) are active from late spring through mid-summer (Figure 3).

Fig 3. Pine tortoise scale crawlers emerging from eggs of females (Auth–Raymond Cloyd, KSU)

After finding suitable locations, nymphs will settle down and start feeding. Nymphs can spread to other pines via wind currents or by attaching to birds. Males, like most scale species, develop into winged individuals that fly and mate with females. Males do not feed and eventually die. There is typically one generation of pine tortoise scale per year in Kansas.

Pine tortoise scale feeding results in yellowing of needles, stunted needle growth, and even death of pines under extensive populations. In general, young pine trees are more susceptible to pine tortoise scale than older (mature) trees. In addition, foliage closer to the ground tends to support higher populations of pine tortoise scale than foliage higher in the tree canopy. Pine tortoise scale produces copious amounts of honeydew, a clear sticky liquid that serves as a growing medium for black sooty mold. Entire pine trees may appear blackened from black sooty mold as a consequence of heavy infestations of pine tortoise scale.

A forceful water spray applied twice per week will quickly dislodge/remove the nymphs and mature females from infested pine trees. Insecticides that can be used to suppress populations of pine tortoise scale nymphs include: acephate (Orthene), acetamiprid (TriStar), bifenthrin (Talstar), cyfluthrin (Tempo), dinotefuran (Safari), imidacloprid (Merit), insecticidal soap (potassium salts of fatty acids), and horticultural oils (petroleum, mineral or neem-based). These insecticides must be applied when nymphs are present to obtain maximum suppression of pine tortoise scale populations and subsequently alleviate future problems.

–by Dr. Raymond Cloyd

The Nantucket pine tip moth, Rhyacionia frustrana, is an insect pest of Austrian and Scots pines in Christmas tree plantations, hedgerows, and landscapes. Nantucket pine tip moth is native to the eastern and southern portions of the USA. Adult moths are 1/4 inches (6.3 mm) long with the head and body covered with gray scales. The forewings are covered with brick-red to copper-colored patches that are separated by irregular bands of gray and white scales (Figure 1).

Fig 1. Nantucket Pine Tip Moth Adult (Author–BugGuide.Net)

Adult moths are active from early evening until dusk and can be found in the canopy of pine trees during the day. Adult females lay white to opaque eggs on shoots, needles, or buds (terminal growth) in spring. Young larvae (caterpillars) that hatch from eggs are 1/16 inches (1.6 mm) long, and cream-colored with a black head. Older or mature larvae are yellow to orange, and 3/8 inches (9.5 mm) in length.

First instar larvae create mines in needles resulting in necrotic spotting. Later, the larvae exit the needles and then tunnel into and feed within the inner tissues of shoots, and buds (Figure 2)

Fig 2. Nantucket Pine Tip Moth Larva (Auth–Raymond Cloyd, KSU)

resulting in branches or shoots turning brown and dying (Figure 3).

Fig 3. Brown Branch Tips and Shoots on Pine Tree (Auth–Raymond Cloyd, KSU)

Damage associated with Nantucket pine tip moth larvae results in deformed growth (stem crooking) (Figure 4)

Fig 4. Deformed Growth or Stem Crooking On Pine Tree (Auth–Raymond Cloyd, KSU)

or a reduction in growth (bushy or stunted growth), which reduces the aesthetic quality and degrades the value of Christmas trees and pine trees in landscapes. Trees can be killed when exposed to repeated Nantucket pine tip moth larval infestations. An indication of a Nantucket pine tip moth infestation is the presence of silken tent-like webbing on shoot tips covered with masses of accumulated plant resin. In addition, fecal deposits may be present in the webbing on the outside of infested shoots. Larvae feed for up to four weeks before pupating. Nantucket pine tip moths overwinter as pupae that are dark-brown and 1/4 to 1/2 inches (6.3 to 12.7 mm) long. The pupae are located in cavities created by larvae within damaged shoots or terminals. Adults emerge (eclose) in about 10 days. There are three generations per year in Kansas.

Management of Nantucket pine tip moth involves implementing proper watering, fertilization, and mulching practices to keep pine trees healthy, which encourages the development of new growth. For minor infestations, you can hand prune infested shoots if branches are reachable. In addition, Christmas trees can be sheared to remove infested shoots.

It is important to monitor adult populations in April using pheromone traps containing a lure that attracts males. Pheromone traps should be placed among susceptible pine trees and inspected weekly. Seven to 10 days after males are captured in the pheromone traps (Figure 5),

Fig 5. Male Nantucket Pine Tip Moth in Pheromone Trap (Auth–Kevin Bauman)

insecticide applications should be initiated. The benefit of monitoring is that it helps time applications of insecticides. Applications of contact pyrethroid-based insecticides (e.g. permethrin or lambda-cyhalothrin) or spinosad must be made weekly for each generation until adult males are not captured in pheromone traps. Insecticide sprays should target young larvae that feed on the outside of shoots. This increases exposure to spray residues before the larvae enter shoots. Consequently, thorough coverage of all plant parts is important to ensure effectiveness of applications. Once larvae are located inside plant tissues, insecticide applications will not be effective because larvae will not be exposed to insecticide residues.