fall 11 / 24:3 - Grand Canyon River Guides

Tamarisk Leaf Beetle Update:Stepping Up Monitoring EffortsSatellites circling the earth have captured imagesof ribbons of green along the Colorado Rivercorridor in Grand Canyon, with over 900 acresof that green dominated by invasive, exotic tamarisktrees (Tamarix spp.). Most of you have seen thesetrees up close and know them intimately. In the pasttwo years, you may have noticed that they are losingtheir foliage earlier than usual. This is a direct resultTamarisk leaf beetle. Photo courtesy NPS.what we have done in the past and taking it to the nextlevel—that of the watershed!In an effort to get accurate information to thepublic and answer questions from the field in a timelyfashion, we will provide bi-annual updates on beetlemovement and response planning in the bqr. Look fora map of the beetle’s current distribution and a summaryof the 2011 movement in the next issue!For now, here is the quick update:• The first beetle larvae were detected in the park in2009, but their manner of arrival is uncertain.• In 2010, beetles were found at stock tanks nearTuweep, up major drainages (e.g. Stone and KanabCreeks), and non-continuously from Glen CanyonDam to Pearce Ferry. Tamarisk defoliation was visibleby late August.• In 2011, beetle sampling was implemented on everypossible science work trip; to date we have sampledbeetles on five river trips; seven trips total by thetime you read this article.• The gaps in distribution from the 2010 map arestarting to fill in this year, with beetles spreading toat least River Mile 208.of tamarisk leaf beetles’ arrival in the park. Whilepurposefully imported into the u.s. to manage tamarisk,National Park Service managers did not activelyrelease them in Grand Canyon. However, we now havethe opportunity to proactively, comprehensively, andthoughtfully prepare for the future.This watershed-scale change brings with it amazingopportunities for multiple stakeholders to be involvedin how we respond to this change, to have input intovarious management actions, and also for people fromvaried backgrounds to work in the field together. Asthis will definitely require a team effort, nps staff wantsto express our gratitude for the early offer of help andsupport that gcrg leaders have expressed. We have agreat relationship to build on. Many gcrg members,commercial companies, private boaters, affiliatedtribes, and individuals have worked alongside nps staffto restore native vegetation at campsites, excavatearcheological sites, remove invasive plants from thecorridor and side canyons, monitor wildlife, delineatetrails, and implement recovery actions for endangeredfish. This could indeed be one of our capstone, multistakeholder,large-scale efforts, truly expanding onTamarisk leaf beetle copulation. Photo courtesy NPS.• No adult beetles or larvae have been detectedbetween Diamond Creek and the park’s boundarywith Lake Mead, but they are very abundantupriver from Lees Ferry in Glen Canyon NationalRecreation Area.• In theory, it should take three to five years fortamarisk mortality, so expect to see defoliatedpage 10grand canyon river guides