Adult Zimmerman pine moths are gray with reddish forewings marked with zig-zag patterned lighter and darker lines. Hindwings are pale yellow-white that is brighter near the edges. Moth wingspans are 1 to 1.5 inches. Larvae of the Zimmerman pine moth are variable in color, ranging from whitish to reddish yellow to green with chestnut brown heads. Larvae also have a series of black dots, at the base of a single bristle or hair. At maturity, larvae are up to 0.6 inches long. Descriptions of the moth's life cycle from Idaho indicate that they emerge from early May through September. Maximum adult moth flight may occur in July. In Connecticut, adult moth flight may be more accurately timed from June to early August. Female moths lay their eggs on the host plant bark, often near wounds in the tree. Newly hatched larvae bore into the terminals or branches and favor those that have already been fed upon by other insects, including white pine weevil. As the larvae grow and mature, they may move several feet through the tree from the original point of entry. Overwintering life stages include larvae of any instar, or eggs if they were laid by females late in the growing season. Those eggs hatch in the spring. Fully mature larvae pupate in their tunnels, close to the surface. The full life cycle takes approximately 1 year from when the eggs were laid (Craighead, 1950).
Host plants of all sizes can be fed upon by the Zimmerman pine moth. Larvae bore into the terminal shoots of their host plants. Injured twigs will leak pitch that is mixed with sawdust like frass from the entrance hole. Shoots that are impacted will eventually turn brown and die. These shoots often break off of the trees. The larvae may also bore into the cambium of the trunk (in addition to branches and twigs) and cause significant damage to the new growth of older trees and may kill younger trees (8 inches or less in diameter). This happens when the bole of the tree is girdled. Areas of attack leak pitch filled with frass and cast (shed) skins of larvae. Pitch pine growing in open areas may be more susceptible to attack than those in dense stands (Craighead, 1950). A single tree may have up to 27 larvae tunneling, and trunks may be honeycombed with these tunnels. In plantations, trees up to 15-20 years of age may be severely attacked.
Sticky traps baited with (Z)-154e161decen31 acetate (Z9–14:Ac) and (Z)-9-tetradecen-1-ol (Z9–14: OH) have been useful at monitoring males of other species in the same genus Dioryctria. Those components were identified as sex pheromones of Dioryctria resinosella (the red pine shoot moth) (Grant et al., 1993). It is possible that a similar pheromone and trapping system could be useful for the Zimmerman pine moth. From June through early August, visually monitor for injured twigs leaking pitch that is mixed with sawdust-like frass from entrance holes created by this insect.
Scotch pine has a lot of genetic variety in the species depending upon geographic origin. Wright et al. (1975) found that fast growing scotch pine from England and central Europe are attacked the most heavily by the Zimmerman pine moth (polonica, hercynica, carpatica, haguenensis, pannonica, and 'E. Anglia'). Of those, more than 60% of the trees were infested and over 50% of them died or became severely misshapen. The next most heavily infested were the slower growing trees from Scotland or northern Eurasia (lapponica, septentrionalis, rigensis, mongolica, uralensis, and scotica). The least damaged varieties in that 1975 study were from southern Europe and Asia Minor (iberica, aquitana, subillyrica, illyrica, rhodopaea, and armena). These varieties have moderate growth rate and green foliage in the winter and summer. Of those, only 3-9% mortality occurred and only 23% were severely misshapen or died as a whole.
Where practical, pruning out and destroying infested tips (to remove larvae) may help reduce the population in a single tree or planting. Reducing additional stressors of susceptible hosts is also important. Proper planting, site selection, maintenance, and watering during drought all help improve tree health and their ability to withstand insect feeding.
Parasitoids of the Zimmerman pine moth have been reported by Schaffner (1959). These include the hymenoptera: Euderus cushmani, Hyssopus thymus, and Scambus hispae. In Indiana, Calliephialtes comstockii, an ichneumonid wasp parasitoid, has been reported attacking Zimmerman pine moth.
Abamectin (NL)
Acephate (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Diflubenzuron (N)
Emamectin benzoate (L)
Lambda-cyhalothrin (L)
Methoxyfenozide (NL)
Permethrin (L)
Tebufenozide (NL)
Active ingredients that may be applied systemically include: Abamectin (injection), acephate (injection), and emamectin benzoate (injection).
When used in nursery settings, chlorpyrifos is for quarantine use only.
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.
