73 . INSECTS OF LODGEPOLE PINE: IMPACTS AND CONTROL Gene D. Amman and • Les Safranylk >Lodgepole Pine jhe species and its management SYMPOSIUM PROCEEDINGS LODGEPOLE PINE THE SPECIES AND ITS MANAGEMENT • SYMPOSIUM PROCEEDINGS May 8-10, 1984 Spokane, Washington, USA and repeated May 14-16, 1984 Vancouver, British Columbia, Canada Compiled and Edited By: DAVID M. BAUMGARTNER, Washington State University, Pullman, Washington, USA RICHARD G. KREBILL, Intermountain Forest and Range Experiment Station, Missoula, Montana, USA JAMES T. ARNOTT, Pacific Forest Research Centre, Victoria, British Columbia, Canada GORDON F. WEETMAN, University of British Columbia, Vancouver, British Columbia, Canada • Symposium Sponsors: Alberta Forest Service British Columbia Forest Service Canadian Forest Service Forest Research Council of British Columbia Intermountain Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture University of British Columbia Washington State University PUBLISHED 1985 .. Additional copies may be purchased from: Office of Conferences and Institutes Cooperative Extension 202 Van Doren Hall Washington State University Pullman, WA 99164-5220 • INSECTS OF LODGEPOLE PINE: IMPACTS AND CONTROL • Gene D. Amman and Les Safranyik harvest, meFchantability can be funher reduced by insects ABSTRACT that bore holes into the wood unless logs are processed promptly (fig. lB). Of approximately 240 species of insects that feed on lodgepole pine, 35 are considered pests or potential pests. 3. GrO'Wth reduction. -Insects that remove large amounts of Nine insect species cause serious damage in periodic, local foliage or those that partially girdle trees reduce growth and infestations and one species, the mountain pine beetle, causes productivity because a longer time is required for a tree to catastrophic losses in repeated outbreaks over most of its reach merchantable size (fig. lC). distributional range. Stand management offers the best 4. Direct killing. -Bark beetles cause large losses in productivity possibility for reducing losses. Seed and cone insects do not by killing merchantable trees and by reducing numbers of extensively affect seed production; nursery stock can be pro­ merchantable trees to the point that harvest of residual trees tected through cultural practices and pesticide treatments. cannot be accomplished profitably (fig. ID). Several insects affecting young stands cause reduced height growth and permanent crooks in stems. Defoliating insects, As the intensity of forest management changes, insect prob· such as the lodgepole needle miner and pine sawflies, usually lems will change also. This fact is already apparent; several in· infest trees of all ages and cause growth loss and some mor· sect species previously considered to be innocuous under natural tality during severe outbreaks. Bark beetles, especially the stand conditions have caused extensive damage when planting mountain pine beetle, pose the most serious threat to and thinning were attempted . lodgepole pine management. Insect species have been divided into groups that affect the different stages in the life of lodgepole pine trees. Only some • of the more imponant species have been included. Nursery pests INTRODUCTION are not treated. These usually are general feeders and are covered in publications such as Sutherland and Van Erden Lodgepole pine, Pinus contorta Douglas, like most trees, pro­ ( 1980). The greatest effort has been placed on the mountain vides habitat for a variety of insect species throughout its pine beetle because of interest generated by severe, almost con· development. These range from moth larvae that feed on seed tinuous losses of lodgepole pine during the past 25 years. For and cones to bark beetles that cause widespread mortality of more detailed descriptions and life histories and for broader mature trees. coverage of insect species affecting lodgepole pine, you are re· Although we know which insect species most commonly af· ferred to Furniss and Carolin (1977) and Evans (1982). Recom· fect different stages of stand development, we lack fundamen· mendations for control of insects by chemical insecticides are tal knowledge of the significance most insect damage will have avoided purposely. Recommendations for use of pesticides on final harvest. The life table approach for forest stands change; some are no longer in effect, whereas improved (Waters, 1969) could be used for an integrated analysis of forest materials and methods are being developed. I stand productivity and an assessment of important agents af. fecting productivity, including insects . INSECTS OF REPRODUCTIVE STRUCTURES • Although animal and weather factors may destroy a large pro· Generally, insects affect productivity in four ways, as il· ponion oflodgepole pine reproductive structures some years, lustrated by the following examples: these losses have a negligible silvicultural effect (Tackle, 1961 ). •• I. Understacking.- Even though large amounts of seed are pro­ Studies of red pine cones suggest destruction of developing duced and large numbers of seedlings emerge, insects that cones by insects may actually enhance flower primordia pro­ destroy seed and seedlings can reduce productivity; losses duction and, consequently, the abundance of future feeding and during early stages of stand development can result in an breeding sites for cone insects (Mattson, 1978). understocked stand at the time of tree harvest. (fig. lA). 1Insecticides used for direct control or preventive sprays are reviewed con· 2. Reduction in merchantability. -Insects that kill terminal tinually by the Environmental Protection Agency. Therefore, persons con· • leaders can cause deformed or multistemmed trees that yield templating use_ of insecticides should ensure that the materials are currently less merchantable wood at time of tree harvest. Following registered for use. - 108 Gene D. Amman and Les Safranyik UNDERSTOCKING MERCHANTABILITY REDUCTION • HARVEST HARVEST / / / / / / / / / / > MORTALITY / / I !:: > ~ 8 I // a: ... / / v TIME A TIME B GROWTH REDUCnON DIRECT KILLING HARVEST HARVEST • / / >..... >..... I/ > > / ~ Q~ Q 8a: a: ... 0.. TIME-------- c TIME D Figure I.-A. Effect of stand understacking on productivity. B. Effect of reduction in tree merchantability on productivity. C. Effect of tree growth reduction on productivity. D. Effect of merchantable tree mortality on productivity. The closed-cone habit of lodgepole pine is at least partially and perhaps the reason damage has been considered low (Keen, responsible for the negligible effect of losses. In stands of 1958) is that few studies of only short duration have been con­ lodgepole pine where the dosed-cone habit prevails, millions ducted. A study of lodgepole pine cones in 1971 found only of viable seed may be stored per hectare for many years (Lotan 2 percent infested by insects (Parker, 1972). Larvae of the moths and Jensen, 1970). Following fire or cuning, this seed then is (Lepidoptera) are the most common insects infesting lodgepole available for seeding the area. In stands where the closed-cone pine reproductive structures. habit is limited, however, seed losses to insects could have a Lodgepole pine cone borer, Eucosma rescissoriana Heinrich • significant effect on attempts to generate some stands. In addi· (Lepidoptera: Olethreutida'!), larvae tunnel in second-year cones tion, some of these insects could become major factors when and feed on the scales and seeds, consuming the softer parts superior tree and seed selection programs for lodgepole pine of cones, leaving the woody veins and paper-thin layers at the are initiated. surface of the cone scales. Larval mines are packed with fme­ Since the Lodgepole Pine Symposium in 1973, a number of grained dark brown frass pellets. Damaged scales may fail to additional species have been reported feeding on the repro­ open at cone maturity, trapping sound seed within the cones ductive structure of lodgepole pine (Furniss and Carotin, 1977), (Hedlin 1981 ). The proportion of damaged cones is • et al., Gene D. Amman and Les Safranyik 109 • usually low, but is found to increase with spacing in western budworms (Stark and Borden, 1965). Cones are often com­ white pine plantations in Idaho. (Ollieu and Schenk, 1966 ). pletely excavated. The adults, which have tan forewings with rust-red mark· When the budworm larvae hatch in late summer, they may ings, emerge and lay eggs on cone scales. Larvae hatch from feed on the needles, and defoliation is the most conspicuous the eggs in about a wee~ and tunnel between cone scales into indicator of the insects' presence. But, if male and female flowers the seed, where they feed on seeds and scale tissue. The dirty and cones are present, those may be preferred feeding sites. Ex­ white larvae may damage more than one cone in completing ternal frass and webbing are signs of infestation. Flowers may development (Hedlin eta/., 1981). They drop to the forest floor be completely consumed and holes bored into the developing to spin cocoons and pupate in September and October. There cones (Hedlin eta!., 1981). the pupae overwinter and development is completed in the spring. Adults emerge in mid-to-late summer and lay eggs that are flattened and overlapping in long masses on the needles. When Laspeyresia toreuta (Grote), one of the seedworms the larvae hatch in late summer, they molt once, without (Lepidoptera: Tortricidae), is associated with seed, upon which feeding, and overwinter in small webbed tents called hiber­ the larvae