Pinon "Pitch Mass" Borer Dioryctria ponderosae Dyar

Photos and Text By: Dr. Curtis Swift, Area Extension Agent (Horticulture)

Order: Lepidoptera
Family: Pyrallidae (Phycitidae) - Pyralid Moths
Subfamily: Phycitinae
Genus & species: Dioryctria ponderosae

The pitch mass borer is reported as a serious pest of pine in the Great plains from South Dakota to Kansas and Colorado (Harrell, 1993). In Western Colorado native populations of Ponderosa (Pinus ponderosae) and pinon pine (Pinus edulis) are attacked. Tunneling activity under the bark weakens the tree with heavily damaged branches and trunks more susceptible to breakage. Girdling of trunks causes deformation and death . Scots (Pinus sylvestris) (AKA Scotch Pine), Austrian (Pinus nigra), and jack pine (P. banksiana) are also reported to be damaged by this insect in the Great Plains.

Masses of a soft, light-pink gum are typical of the feeding activity of this insect.

Eggs are laid near wounds due to improper pruning cuts, mechanical damage or porcupine injury. In landscape plantings, over-irrigation increases pitch mass borer infestations possibly due to increased succulence of the trees.

A Nebraska study (Harrell 1933) indicated infestation and damage levels are higher in non-native stands. Harrell suggests the possibility that greater stress in non-native stands makes the trees more susceptible to borer infestation. Of the four species of pines examined in this study (ponderosa, Scotch, Austrian and jack) the first two had higher infestation levels. The reasons for this increased infestation is not clear, but Harrell mentions the following:

• these pine species may differ sufficiently in their chemical nature resulting in greater attraction of the borer
• these pines may differ sufficiently allowing greater survival of the insect
• the chemistry of these pines may have been altered in favor of the insect due to stress

The one-half to three-quarter inch adult moths are gray-brown with white zigzag markings. Their mouth parts are somewhat snout-like giving this group the common name of snout moths.

The larvae range from a dirty white to pink in color with a light brown head. This stage of the insect resides under the pitch masses and can be exceedingly difficult to locate.

The life histories of the various species of Dioryctria are poorly understood making control difficult (Harrell 1996). Information in Furniss and Carolin (1977) regarding the Pinon Pitch Mass Borer (D. ponderosae) is incorrect. The information provided relates to D. tumicolella not D. ponderosae. The following discussion relates to Dioryctria ponderosae, the Pinyon (Pinon) `Pitch Mass' borer and provides the most current information available.

In Nebraska this insect has a life cycle of 14 to 24 months depending on weather conditions (Harrell 1996). In Colorado, Cranshaw, et. al. indicate most require at least two years to complete the cycle from egg to adult. Egg laying occurs from late June through August. Eggs are laid singly on the underside of bark scales, on the trunk or on the branches.

Larva hatch in one to four weeks and immediately begin boring into the stem (Harrell 1996). Other species of Dioryctria are known to overwinter in a hibernacula ¹ and bore into the tree the following spring. Most tunneling occurs beneath a branch or near a wound or site of previous attack.

After undergoing what appears to be five larval stages, the larvae pupate in silk-lined chambers in their tunnels or in the pitch mass. Pupation takes place during May, June, and July. Adults emerge after pupation and egg laying begins shortly thereafter.

Pruning should be avoided during the active flight period of late June through August when egg laying occurs. When branches are removed, pruning should be done in such a way to enhance wound closure.

Stress should be avoided to reduce the attractiveness of the trees to the borer. Over-watering, root injury due to road cuts, trenching, compaction, and other factors resulting in stress should be avoided. During exceptionally dry years, watering may be needed to prevent root and needle dehydration. Care should be taken to avoid over-watering.

Preventative trunk sprays of Maverick have been found effective with Cranshaw (personal communique) indicating any of the pyrethroids (e.g. Astro, Talstar, Tempo or Scimitar) the treatment of choice. Sprays should be applied to the trunk and larger branches paying particular attention to wound areas and the underside of branches where the branch and trunk join. Sufficient spray should be applied to thoroughly wet the bark. Pitch Mass Borer infestations cannot be eliminated with sprays as the larvae are under the bark and protected by pitch.

Cranshaw, et. al. recommend two or more insecticide treatments each season over at least two years to reduce the infestation. Cranshaw (personal communique) recommends a treatment "when adult emergence/egg laying is suspected (should begin late June), with a second treatment in late summer due to the extended egg laying period."

Applications of EC (liquid) formulations should be avoided due to the possibility of needle injury. Wettable powder formulations are recommended. They are mixed with water and applied as a spray but lack the emulsifying agents responsible for stripping wax from needles resulting in needle burn.

The use of a flexible wire to search out tunnels and crush individual borers has been recommended as has the use of moth crystals pressed into borer pitch masses. The paradichlobenzene formulation of moth crystals should be used if the later technique is attempted. Soil injections of dimethoate has shown promise in ridding infested trees of the Pitch Mass Borer.

Other Western forest species of Dioryctria are reported to attack cones, shoots, foliage and trunks of various trees. According to Furniss and Carolin, Pine (Pinus), Douglas Fir (Pseudotsuga), Fir (Abies), Spruce (Picea) and Hemlock (Tsuga) are attacked by this insect.

The Colorado, the Zimmerman moth, (Dioryctria zimmermani) another pest of pine, especially Scots and Austrian, causes popcorn-like masses of sap on trunks and branches.

1. Hibernacula - a tiny cocoon spun by the caterpillar (first or second instar) as a shelter for the winter.

References Used:

Cranshaw, W. D. Leatherman, B. Kondratieff. Insects that feed on Colorado Trees and Shrubs. Bulletin 506A, Colorado State University Extension
Borror, D.J., C.A. Triplehorn & N.F. Johnson. 1989. An Introduction to the Study of Insects: Sixth Edition. Saunders College Publishing
Furniss, R.L. & V.M. Carolin. 1977. Western Forest Insects. Miscellaneous Publication No. 1339. USDA - Forest Service.
Harrell, M.L. 1993. Influence of pine host species on infestation and damage by Dioryctria borers (Lepidoptera: Pyralidae) in the Central Great Plains. Environmental Entomology 22(4): 781-783.
Harrell, M.L. 1996. Life Histories and Parasitoids of Dioryctria Borers (Lepidoptera: Pyralidae) of Pines in Nebraska. Journal of the Kansas Entomological Society. 69(4): 279-284.
Wawrzynski, R.P., A.D. Kahn, W.S. Cranshaw, & D.A. Leatherman. 1986. Insect Pests of Colorado Trees. Bulletin 506A. Colorado State University Extension.

Placed on the Internet August 25, 1997
Updated July 11, 2009