Cheyenne Canyon Tussock Moth Control Project Analysis for Pollinators and Other Non-Target Species Pike National Forest, Pikes Peak Ranger District El Paso County, CO Prepared by: Steven Olson, PSICC Forest Botanist 10 May 2016; Update 05/16/16 Purpose and Need: The purpose of this project is to minimize the spread and intensity of the Douglas-fir Tussock Moth outbreak in the Colorado Springs area. The project is needed to complement state and local agency and landowner efforts to control the moth. The greater Colorado Springs area is mosaic of private, city, state, and federal lands. The juxtaposition of different landownership, as well as divergent management objectives among local, state, and federal agencies, requires a high level of collaboration and communication to control the current outbreak. The Tussock Moth causes defoliation and kills Douglas- fir and other coniferous trees. These trees are a valued component of the scenic backdrop for the communities, enhance recreation values, and provide watershed protection and wildlife habitat. On National Forest lands, the Tussock Moth outbreak is immediately adjacent to private, municipal, and state lands; lies within the Wildland Urban Interface; and is occurring within a heavily-used recreation area. There are concerns that the outbreak may continue to spread on National Forest lands and onto adjacent private, city, and state lands. The project is intended to minimize additional Douglas-fir mortality on the Pike National Forest adjacent to current infestations. The Tussock Moth is a native defoliator with well documented outbreaks occurring in Colorado since at least the 1930’s. These outbreaks typically last for two to four years. On the Pike National Forest, the 1993 to 1996 outbreak resulted in 30 to 40 percent Douglas-fir mortality, affecting 18,000 acres. Other outbreaks have been smaller and more isolated. The current outbreak was first noticed in 2014 on Cheyenne Mountain State Park and Cheyenne Mountain Air Force Station land. The current Cheyenne Canyon Tussock Moth infestation covers approximately 1,000 acres across private, city, state, and federal land ownership. In the Cheyenne Canyon area, there are approximately 50 acres of infestation on National Forest lands. There are mixed stands of ponderosa pine, Douglas-fir, and white fir adjacent to existing infestations that could potentially be affected by spread of the Tussock Moth. Within the project area there are old growth Douglas-fir and Douglas-fir plantations that are now 80 to 110 years old. Treatments within the project area would maintain desired forest structure by protecting high-value trees, including old growth and large diameter Douglas-fir adjacent to current infestations, and complement moth control actions on nearby lands under state, local and private ownership. Proposed Action: The Pike & San Isabel National Forests and Cimarron & Comanche National Grasslands propose to implement control measures to minimize the spread and intensity of the Douglas- fir Tussock Moth outbreak on National Forest System Lands within the Wildland Urban Interface near Colorado Springs. The Project Area encompasses 408 acres near Cheyenne Canyon in El Paso County, Colorado. The affected areas are in portions of T14S, R67W, Sections 28, 29, 32, and 33; and T15S, R67W, Sections 4, 5, 9, and 10. The attached map (Figure 1) shows the current outbreak and the areas on National Forest System Land that are proposed for treatment. 1 In separate actions, treatments are scheduled to occur on private, city, and state lands adjacent to the National Forest. Those treatments are separate from this proposal and are not part of the Forest Service proposed action. Control of the moth would be accomplished using Foray 48B Biological Insecticide. The insecticide would be applied from the air by helicopter. A single treatment would occur during the period when treatment would be most effective, which is most likely to happen during the month of June 2016. No application would occur in areas where surface water is present, including ponds, lakes, and wetlands and perennial, intermittent, and ephemeral streams. A 100 foot no spray buffer on either side of all perennial and ephemeral streams will be applied. Best management practices and all EPA label directions will be strictly followed. The treatment area would be closed to the public during the period of aerial application. Figure 1. Project area map for the Cheyenne Canyon Tussock Moth Control Project. 2 EXTRAORDINARY CIRCUMSTANCES DISCUSSION There are no established research natural areas in the area and there are no plants listed under ESA in the area. PROJECT AREA DESCRIPTION The proposed project area is within the ecotone of the Pikes Peak-Rampart Range and the Northern Arkansas Granitics ecological subsections as defined by McNab, et al. (2007). The area lies within the Cheyenne Creek sixth level watershed. The project area is in a montane climate zone at elevation between 7,000 and 8,500 feet. All aspects are present in the vicinity, and slopes may be over 60 percent. This area is underlain by rocks of the Pikes Peak batholith (Tweto 1979). Soils in the vicinity are mapped as being in the Herbman, Legault, Rock outcrop, and Sphinx series. These soils are derived from weathered Pikes Peak granite (Moore 1992). Vegetation is described as mixed conifer, Ponderosa Pine-Douglas-fir, Ponderosa Pine/Gambel Oak, and Ponderosa Pine/grass dominated. There are plantations of 80 to 110 year-old Douglas-fir and large diameter Douglas-fir intermixed with Ponderosa Pine and White Fir. EFFECTS ANALYSIS Douglas-fir Tussock Moth Caterpillars of Douglas-fir Tussock Moth (Orgyia pseudotsugata) feed primarily on Douglas-fir, true firs (here, White Fir), and spruce. When these have been largely defoliated, caterpillars will choose other conifers. Eggs overwinter in a mass, and hatch about the time of leaf expansion. Caterpillars feed on newly emerging leaves, but will also consume older leaves. They pupate in summer, and moths emerge in late summer. Males fly mostly in the afternoon. Female moths are flightless. There is only one generation per year. Because of these factors, the rate of spread of infestations is usually slow. Populations of tussock moth are usually held at low levels by natural means, but outbreaks occur at irregular intervals of 15 to 20 years. The outbreaks develop rapidly, and generally last two to four years before a native virus causes the infestation to crash. Outbreaks have remained active for up to seven years in rare cases. They may kill up to about 40 percent of the host trees in affected stands. Reduction in growth rate of trees within infested areas has been observed, but the normal growth rate can return within five years (Cook 2003). Defoliated trees may be more susceptible to bark beetle attack. Bacillus thuringiensis var. kurstaki There are several strains of Bacillus thuringiensis (Bt). The potency of different varieties of Bt varies with the insects. The crystalline (Cry) proteins in Bt crops target Lepidoptera and Coleoptera. Bacillus thuringiensis subsp. kurstaki, also known as Btk, is a native species that affects only Lepidoptera. “Btk vegetative cells produce spores and crystals. After the insect consumes the crystals, toxins are formed that attach to the mid-gut of the insect and rupture cell walls. The Btk spores germinate in the intestinal tract and enter the body cavity through the perforations made by the crystal toxins. The bacteria replicate in the body cavity, causing septicemia and eventual death” (Durkin 2004). Btk treatment Durkin (2004) provides a comprehensive summary of literature discussing the effects of Btk treatments, and is the source for much of the following discussion. It is worth noting that laboratory exposures are 3 typically many times higher than would be seen in field use of Btk (Duan, et al., 2008). Most field studies have looked at diversity at a given site, not in the context of a larger landscape (Manderino, et al., 2014). Uniform coverage by aerial treatment with Btk is probably infrequently achieved. Highest residue of treatments is in short grasses, which may lead to longer periods of exposure. There are cases where Btk treatments have not been effective (Valaitis and Podgwaite 2011). The bacteria may persist in the soils for over a year following application (Addison and Holmes 1996). Btk’s short period of activity depending on sun exposure and rain should help minimize impacts to non-target Lepidoptera. Mortality rates of caterpillars in shaded situations are greater than in brightly lit areas due to the breakdown of Btk under sunlight (Durkin 2004). Studies have shown residual effect of Btk last 2 to 10 days, but has been reported for up to 30 days. There are fewer non-target species effects from aqueous formulations of Btk. Direct Effects of Btk treatment Plants There is no information on direct negative effects on terrestrial plants. No impacts to plants have been observed, so there has been little incentive for study on the effects of Btk to plants. Invertebrates Effects of Btk on insects other than Lepidoptera are generally minor (Durkin 2004). Earthworms were not affected during a 10 week long study with 1,000 times the expected environmental concentration of Bt using a water-based formulation (Addison and Holmes 1996). By extension, similar population reductions could possibly occur with other soil invertebrates (Durkin 2004). There is no information on negative effects on soil microorganisms. No Cry proteins in Lepidoptera or Coleoptera targeted Btk formulations have been shown to have any effects on honeybees (Duan, et al. 2008). This holds true for both adult and larval honeybees. Except for the possible effect of an ant-targeted Cry toxin, none have been observed impacting any Hymenoptera. In a study of ants, there was no effect on abundance, composition, diversity, or species richness over a three year period (Durkin 2004).