FFoorreesstt HHeeaalltthh PPrrootteeccttiioonn Report 01-6 May 2001 CONE AND SEED INSECTS AND THEIR IMPACT ON WHITEBARK PINE Sandra Kegley, Nancy Sturdevant, Jack Stein, Beth Willhite, Paul Flanagan, Julie Weatherby, and Michael Marsden ABSTRACT INTRODUCTION Whitebark pine, Pinus albicaulis Engelm. is an Whitebark pine, Pinus albicaulis Engelm., plays important but declining high-elevation tree a key role in the survival and distribution of species in western forests. Regeneration of this wildlife species such as the grizzly bear (Ursus species has been difficult and the impact of cone arctos horribilis Ord), Clark's nutcracker and seed insects unknown. Seven sites (Nucifraga columbiana Wilson) and the red selected from the geographical range of squirrel (Tamiasciurus hudsonicus) by providing whitebark pine in Idaho, Montana, Washington, a high protein food source with its seeds and Oregon, and California were examined for cone cones (Tomback 1978, Kendall 1983). Kendall and seed insects and their impact. Ten different and Arno (1990) indicate that long-term declines insect species were found affecting various in cone production may affect wildlife community reproductive structures of whitebark pine. dynamics and emphasize the importance of Insects having the greatest impact across most adequate and consistent cone crops. As one of sites were fir coneworm (Dioryctria abietivorella few tree species that grow in the subalpine (Grote)) and western conifer seed bug community, whitebark pine plays an important (Leptoglossus occidentalis Heidemann). role in watershed stabilization (Mumma 1990) Coneworms infested up to 68% of cones and recreation and esthetic values (Cole 1990). collected, destroying up to 13% of the seed Research has recently documented the rapid extracted. Seed bugs damaged up to 27% of decline of this important species throughout the seeds. Pheromone traps for the ponderosa much of the West. The decline is due primarily pine cone beetle (Conophthorus ponderosae to the introduced white pine blister rust fungus Hopkins) and coneworms were tested. (Cronartium ribicola Fisch.), periodic outbreaks Ponderosa pine cone beetles were trapped at of mountain pine beetle (Dendroctonus three of seven sites. Coneworms were trapped ponderosae Hopkins), fire suppression, and at two sites where pheromone traps were forest successional processes (Keane and Arno deployed. Further studies incorporating different 1993). cone crop levels of whitebark pine and other associated tree species are needed to fully Regeneration of this species can be difficult determine the effect of cone and seed insects on because of many competing biological and whitebark pine seed and reproduction. cultural factors such as poor germination rates, United States Forest Northern 200 East Broadway Department of Service Region P.O. Box 7669 Agriculture Missoula, MT 59807 slow growth, sporadic cone crops, and the beetles destroyed 50-80% of limber pine (Pinus widespread decline mentioned above. Cone flexilis James) cones in some years (Keen production in whitebark pine is characterized by 1958), and coneworms infested up to 40% of the frequent years of small cone crops and less cones (Nebeker 1970). Cone beetles can frequent years of moderate to heavy crops. destroy 90% or more of the western white pine Clark's nutcracker plays an essential role in the (Pinus monticola Dougl.) cone crop (Shea et al. dispersal of whitebark pine seeds. Whitebark 1983, Williamson et al. 1966). Seed bugs and pine seeds sustain these birds during much of coneworms impacted between 50-80% of cones the year, but a large portion of the seeds that in western white pine seed orchards (Connelly have been cached germinate and become future and Schowalter 1991, Haverty et al 1986). whitebark pine regeneration (Arno and Hoff 1989 ). Hutchins (1990) found that Clark's The objectives of this study were to identify nutcracker harvested 36% of seeds in forested insects affecting reproductive structures, to tracts and up to 99% of seeds from open grown quantify the impact of insects, to note the stage trees. Cone and seed insects may threaten of cone development and seasons in which successful regeneration of whitebark pine by infestations occur, and to evaluate the efficacy reducing seed production during some years. of pheromone traps for monitoring cone beetles Likewise, bears, nutcrackers, and other wildlife and coneworms in whitebark pine habitats. species which use whitebark pine seed as an METHODS important food resource may also be negatively affected by the activity of cone and seed insects. Seven sites were selected from the geographical range of whitebark pine in Idaho, Montana, Whitham and Mopper (1985) found that the Washington, Oregon, and California. We coneworm, Dioryctria albovittella (Hulst), selected sites based on accessibility and significantly reduced cone production in pinyon number of whitebark pine trees of cone-bearing pine (Pinus edulis Engelm.). In addition to direct age. Sites varied in elevation, aspect, slope impacts of cone and seed insects, there is position, and latitude (Table 1). Fifteen trees potential of indirect effects such as birds were randomly chosen at each site. There were avoiding foraging on insect infested cones 14 treatments on each tree, with each tree thereby affecting seed dispersal. Christensen serving as a treatment replicate. Treatments and Whitham (1991) found that birds avoided consisted of exposing cones to insects for pinyon pine trees with insect-infested cones and various time periods during the 2-year cone sometimes avoided entire infested stands. development period. Most treatments consisted Prior to this study, information on the incidence of exposure periods of approximately 1 month and impact of insects on first- and second-year occurring at different months throughout the 2­ whitebark pine cones was largely unknown. year growing season. Some treatments However, several insects were thought to be exposed cones during an entire year of the 2­ probable associates. The western conifer seed year growing period (exposed first or second bug, Leptoglossus occidentalis Heidemann, and year) or exposed cones during both years. coneworms, Dioryctria spp., are likely pests of Some cones were protected during both years. first year conelets. Second year cones might be During the second year of cone development, infested by the ponderosae pine cone beetle, cones in all but two treatments were caged to Conophthorus ponderosae Hopkins; cone prevent foraging by Clark's Nutcracker. In order moths, Eucosma spp.; seed worms, Cydia to apply treatments to cones that were mainly (=Laspeyresia) spp.; coneworms, Dioryctria located in the upper crown on trees at all sites spp.; western conifer seed bug, Leptoglossus except Ball Mtn., it was necessary to climb the occidentalis; and seed chalcids, Megastigmus trees. spp. (McCaughey and Schmidt 1990). Cone 2 During 1995, when cone buds became treatment were tallied and monitored for losses prominent or flowers appeared in June and July during the first year. Flower and conelet losses 1995, individual branch tips were flagged to at other sites were not quantified. Branches with designate 14 flower clusters (treatments) on cone clusters were wrapped with cotton bands each of the 15 trees. Ripe pollen catkins were below the cone clusters. Fine mesh cloth bags collected in June, then dried, and pollen was were slipped over the branch tips and secured extracted. Flowers in each cluster were with plastic bar-locks over the cotton bands, artificially pollinated to ensure cone production. enclosing the cones (Figure 1). All cones were At Ball Mtn., the number of flowers selected for harvested in September 1996. Table 1. Whitebark pine site characteristics. Elevation Latitude Site State (feet) (degrees) Aspect Slope Position Gisborne Mtn. ID 5,430 48 SE-SW Upper Seven Devils ID 8,000 45 W-NW Upper Snowbank Mtn. ID 7,525 44 E-SE Ridge Top Daisy Pass MT 9,500 45 S-SW Bench Stormy Mtn. WA 6,100 47 S-SW Ridge Top Mt. Hood OR 5,430 45 S-SE Bench Ball Mtn. CA 7,682 41 W-NW Upper Figure 1. Mesh cloth bags covering cone clusters to prevent insect attack. Harvested cones were placed in individual sacks dissected and seeds extracted and counted. along with the designated tree, treatment Seeds were categorized as normal, number, and study site. Cones from each undeveloped, aborted, damaged by seedworms, treatment cluster were examined to determine or damaged by coneworms. Seeds from each the number of live cones, number of cones with cone were saved, pooled by treatment on each external evidence of insect damage, and tree within a site, and placed in an envelope. A number of cones damaged by birds. Cones random sample, up to 100 seeds from each were measured and cone scales were counted treatment per tree, were radiographed. The x- to determine potential seeds. Cones were then rays of each treatment/tree combination were 3 sent to the Institute of Forest Genetics, of insect and bird damage. Percent infestation Placerville, California for interpretation. X-rayed was determined for all cones sampled. seeds were classified as filled (normal), physiologically abnormal, damaged by seed The impact of insects and other agents on bug, seed chalcid, seedworms or coneworms, whitebark pine was reported as the percent of damaged by birds, or mechanically damaged. cones or seeds damaged by each agent. In Identification of seed bug damage by x-rays can such data (a variable that estimates a be difficult and sometimes confused with other percentage or proportion) the variance is a types of physiological abnormalities. The x-ray function of the mean. To eliminate this interpreters were conservative in their definition dependence, the data was transformed using of seed bug damage and made a second the arcsine of the square root of the proportion. category referred to as "potential seed bug Adjustments for small samples were also made damage." This described damaged seeds with as recommended in Snedecor and Cochran symptoms similar to seed bug feeding. Seed (1971). Due to technical difficulties in pollination bug and potential seed bug damage are (timing, adverse weather), abortion of flowers or reported and analyzed separately.