IInformationnformation forfor pestpest managementmanagement pprofessionalsrofessionals aandnd ppesticideesticide aapplicatorspplicators GGreenreen BBulletinulletin Vol. 1 ● No. 5 ● December 2010

Ground Squirrel Management Highlighting the Connection between Effective Control and Water Quality Issues

alifornia ground squirrels (Fig. 1) Care found throughout most of the state. Th ey are native and quite adaptable to most of California’s diverse environments. Th ey can live in close association with people and feed on crops and ornamental plants. A major problem associated with squirrels is their burrowing activity that can damage irrigation systems, landscapes, and other structures. When they cause these problems, L. L. Lima, UCCE control oft en is necessary. Figure 2. Burrow entrance. Ground squirrels prefer dry climates and do not like areas with high soil moisture. Most of our irrigation systems, especially drip and sprinkler, do not create the continuous soil moisture that would deter squirrels from the area. Squirrels also are good W. P. Gorenzel, UC at burrowing just outside the irrigated Figure 1. California ground squirrel. area or on slopes and other relatively dry places. Squirrels impact water use water. Contamination of subsurface mostly by chewing on plastic pipes water has not been identifi ed as a R. S. Krason, UCCE or burrowing in levees, berms, and problem with rodenticide use. Figure 3. Burrowing damage beneath a bridge. other water structures. Because of their close association with irrigated Dealing with ground squirrels takes vegetation, but in the summer and fall, areas, squirrel burrowing can lead to a good understanding of the animal they like seeds. Knowing these changes soil movement into water systems. and the control options available. will help in understanding their Improper use of rodenticides such Ground squirrels have a distinct seasonal activity and also in selecting as broadcasting into waterways also activity pattern throughout the year. the appropriate control strategy. can lead to contamination of surface Basically they hibernate in the winter, breed during the early spring, mature Ground squirrels live in underground during the summer, and collect seeds burrows (Figs. 2 and 3). Oft en during the fall. Some adult squirrels burrows interconnect and are home WHAT’S INSIDE ... go into a summer hibernation to avoid to several squirrels. Burrow systems Controlling Pocket Gophers | Page 4 the heat, but the young ones remain usually are clumped together to form active, even during hot summer days. a squirrel colony. Once established, Red Palm Weevil Alert | Page 5 Another important seasonal activity the squirrel colony can remain in is their feeding preferences. During that area for many years. Squirrels Ask the Expert! | Page 5 the spring, they prefer fresh green ... continued on the next page Page 2 | December 2010 fumigant or gascartridge isthe is quite eff is relatively burrow high, fumigation springDuring or soil moisture when Burrow Fumigation burrows for recent activity. burrowtheir systems. Check the controlled, the fi you squirrels decidethe needto be guide your control decisions. When most eff diff when and4–English Fig.5–Spanish) shows Th applied inor near active burrows. mostcontrolbecause eff It’s important to fi there usually isaburrow nearby. burrow,their you when them, so see usually remain within 150feet of ... continued from the previous page Figure 4.Control calendar wheel, English. econtrol calendar (Fig. (wheel) ective. Refer to it to help erent control are methods ective. Th rst step isto locate nd the burrow,nd the e simplest orts are requires one feeding eff to be phosphide bait isfast acting and usually are attracted to Zinc them. oats or squirrels grain-based pellets, commonly baits Since used. these are rodent bait is eff In late spring and early summer, Rodent Bait restrictions carefully. restrictions material. Follow label directions and Specials restrictions apply to this eff fumiganta restricted use that isvery treatment. Aluminum phosphide is active one to two days aft Re-treat burrows that remain or other fl don’tso around grass them use dry Th treated for eff carefully. Allburrows needto be smoke bomb. Follow instructions use ese cartridges produce cartridges ese fl ective incontrolling squirrels. ammable materials. ective control. Caution: ective and er initial ames, ective. It Figure 6.Ground squirrel bait station. treatment around active burrows phosphideZinc isapplied by hand it only should used once be ayear. eating zinc phosphide bait again, so itsublethal dose, willshy away from downside isthat squirrel ifthe gets a do not get accessto bait. the One is neededto ensure other animals is arestrictuedand pesticide, use care L. L. Lima, UCCE UCCE L. Lima, Page 3 | December 2010 ective ective —Terrell P. Salmon, P. —Terrell [email protected] UC Wildlife Specialist, Emeritus, Specialist, UC Wildlife ective placed directly in squirrel burrow burrow in squirrel directly placed areas other and parks In openings. some frequent, the public where traps destroy and disturb people a to their opposition because of program. management as Options Aren’t Other Eff no are there Unfortunately or plants, toxic repellents, eff are devices that frightening keep to or squirrels of area ridto an Even plants. on feeding them from and fumigants, trapping, using so, problems squirrel solve can baits in other and farms, homes, around a problem. they where are areas ective squirrel squirrel ective e California California e ort to control many many control to ort pets or other wildlife. To ensure bait bait ensure To wildlife. other pets or a second several days, for is available bait Follow will be necessary. baiting do Anticoagulants instructions. label poisoned in the tissues of accumulate be should so all carcasses rodents, buried. or removed Trapping eff be an can Trapping takes it method although control eff of a bit quite Game Fish and of Department squirrels ground releasing prohibits are unless you areas other into permit, something a written granted be can Traps is very unlikely. that Some are grains. or nuts with baited squirrels. While live traps are sold for sold for are traps live While squirrels. recommended not theysquirrels, are the disposalbecause of problem Th squirrels. live with squirrels if the ective ected. Anticoagulant baits baits Anticoagulant ected. nd them easily. Broadcasting Broadcasting nd them easily. require multiple feedings over several over feedings multiple require shyness is no bait there While days. be they can thesewith materials, ineff rendered or by broadcasting bait throughout throughout bait broadcasting by or An important colony. the squirrel zinc phosphide fact with positive in accumulate does not it is that tissues, so squirrel’s the poisoned likely not are scavengers or predators to be aff several over bait enough get don’t several over bait supply To days. used either are anticoagulants days, the (Fig. 6) where station in a bait bait eat to go and come squirrels baiting broadcast or hand by or Squirrels burrows. active around seeds and for foragers excellent are will fi it and very it sparsely, spreads bait to pose does not generally a hazard Figure 5. Control calendar wheel, Spanish. wheel, calendar 5. Control Figure Trapping to Manage Pocket Gophers

ocket gophers (Th omomys spp.) eff ective in a given setting, although P are one of the most damaging some have proven more eff ective vertebrate pests in California. than others. For example, a recent Gophers are short, stout burrowing University of California Cooperative J. K. Clark, UC rodents, usually 6 to 8 inches long Extension study found that the Figure 1. Pocket gopher (Th omomys spp.) (Fig. 1). Th ey spend most of their Gophinator trap outperformed the excavating its burrow system. time below ground where they use Macabee® trap due to its ability to their front legs and large incisors to capture larger gophers at a higher create extensive burrow systems. rate; both traps captured small gophers equally well and required Pocket gophers cause extensive and an equivalent amount of time to set. quite varied forms of damage that includes girdling of stems and vines A similar study conducted by below ground, consumption of tap the USDA National Wildlife roots and aboveground vegetation, Research Center compared three and mounding that poses a serious traps—Macabee®, Cinch, and hazard to landscapers, homeowners, Blackhole©, a style of box trap. and the general public. Th ey found the Cinch trap to be most eff ective, although it took longer to set and required more Trapping is one of excavation for placement. Selection R. A. Baldwin, UC the best methods of an appropriate trap will vary Figure 2. Types and brands of gopher traps “ depending on the user’s needs, include (clockwise from upper right) Victor® to use in urban/ but the Gophinator trap appears Black Box™, Macabee®, Go phinator, and Cinch. suburban settings. to provide an eff ective and quick option for gopher control. carrot oil, and a grapefruit-based attractant showed no diff erence A number of options are ” Other factors to consider in capture success. Th is does not available for controlling pocket Th ere also has been debate about preclude potential benefi ts from gophers such as fumigation, toxic the need to cover hole openings other attractants but certainly, at a baits, and trapping. All three aft er setting traps. Recent tests have minimum, indicates that attractants methods have their advantages and shown little infl uence of leaving are not needed to eff ectively capture could be included in an integrated holes uncovered vs. covering them pocket gophers. pest management program for up. If you are able to leave them controlling pocket gophers. Trapping provides a relatively uncovered, this will save time However, trapping is one of the best safe and effi cacious approach to in setting and checking traps. methods to use in urban/suburban pocket gopher control, although However, in many cases, trappers settings given its high effi cacy, it does take practice and patience will prefer to cover holes to limit minimal risk to children and pets, to become profi cient. If you are access to pets and children. Clearly, and lack of potential runoff from interested in further details on in these cases, covering trap-sets is gopher-related rodenticides. gopher trapping, check out the UC warranted. IPM Pest Note Pocket Gophers at Which trap to use? Th ere also appears to be little http://www.ipm.ucdavis.edu/PMG/ A number of pocket gopher benefi t to using many proposed PESTNOTES/pn7433.html. traps currently are available for attractants for gopher trapping, —Roger A. Baldwin, purchase including the Macabee®, as recent tests comparing trap- Wildlife Pest Management Advisor, Gophinator, Cinch, and a variety sets with no attractant to trap-sets UC Statewide IPM Program, of box traps (Fig. 2). All can be baited with peanut butter, anise oil, [email protected] Page 4 | December 2010 Page Thank you in advance for your help.

Ask the Expert! INVASIVE PEST ALERT! I’ve been fi nding large mounds of fresh soil (about 6 to 12 inches in diameter) Red Palm Weevil Q in my customer’s turf. How can I determine what is causing the problem? Red palm weevil (RPW), Rhynchoporus ferrugineus, A Mounds of fresh soil are typical indicators that there (Fig. 1) has been detected in might be a vertebrate pest present. If the mounds are California. Worldwide, the crescent or horseshoe shaped when viewed from above, RPW is considered the most the pest is most likely a pocket gopher. If the mounds destructive pest of palms. are more circular in shape when viewed from above and RPW is a native of Southeast have a volcano-shaped profi le, the pest is most likely a Asia, and its discovery in a mole. For more information about pocket gophers and residential planting in Laguna moles see articles on the UC IPM Web site, http://www. Beach is the fi rst time this ipm.ucdavis.edu/PMG/menu.vertebrate.html. weevil has been found in the USDA United States. Th e presence Figure 1. Adult Red Palm Weevil. Q My clients have reported damage on of the red palm weevil in their property that they suspect might California represents a serious be caused by ground squirrels. Where can I get information on how to manage threat to common types of California ground squirrels? landscape palms and to the date palm industry. UC has several resources devoted to California A ground squirrel management. Visit your local UC Female RPWs bore into the trunks of palm trees, forming Cooperative Extension offi ce, access the UC IPM Pest holes to lay their eggs. Each Note about California ground squirrels (http://www. female can produce an average ipm.ucdavis.edu/PMG/PESTNOTES/pn7438.html), or of 250 eggs, taking about three visit the California Ground Squirrel Best Management days to hatch. Larvae (Fig. 2) USDA Practices Web site at http://groups.ucanr.org/gsbmp. emerge and chew into the tree, Figure 2. Larvae and pupae. How can I develop an effective strategy making tunnels up to a yard Q for managing rats? long. Aft er about two months of feeding, larvae pupate A successful rat management program includes sanitation inside the tree for about three A measures, building construction and rodent proofi ng, and, weeks before the reddish- if necessary, population control including trapping and brown adults emerge; their baiting. For details about how to create a rat management color varies from black to dark program, view the UC IPM Pest Note Rats at http://www. orange. Adults live for two ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html. to three months, feeding on palms, mating multiple times, Have a question? E-mail it to [email protected]. and laying eggs. How YOU can help University of California Supported by the University of Statewide IPM Program California Statewide IPM Program One Shields Avenue and the California Department of During your normal day-to- Davis, CA 95616-8621 Pesticide Regulation through the Urban Pesticide Runoff Mitigation day duties, keep an eye out for Phone: (530) 752-8350 and Outreach Project. signs of this pest. Th e most ? The contents of this document visible signs are excessive E-mail: [email protected] do not necessarily refl ect the views and policies of UC IPM or CDPR dead and dying palm fronds Online: www.ipm.ucdavis.edu nor does mention of trade names (Fig. 3), a wilting palm crown, or commercial products constitute endorsement or recommendations chewed fi ber or sawdust for use. falling from the tree, oozing brown sap, and exit holes. In heavily infested trees, fallen The University of California prohibits discrimination against or pupal cases and dead adult USDA harassment of any person on the basis of race, color, national origin, weevils can be found around religion, sex, physical or mental disability, medical condition (cancer Figure 3. Red Palm Weevil has severely related or genetic characteristics), ancestry, marital status, age, sexual the base of the tree. damaged this palm. orientation, citizenship, or status as a covered veteran (special disabled veteran, Vietnam-era veteran, or any other veteran who served on active duty during a war or in a campaign or expedition for which a campaign If you see and/or suspect badge has been authorized). any signs of the RPW, please report these fi ndings to the California University policy is intended to be consistent with the provisions of Department of Food and Agriculture’s (CDFA’s) Pest Hotline at 1-800- applicable state and federal laws. Inquiries regarding the university’s nondiscrimination policies can 491-1899 or go to the CDFA’s Report A Pest Web site, http://www. be directed to the Affi rmative Action/Staff Personnel Services Director, cdfa.ca.gov/go/reportapest. You also can call your local Agricultural University of California, Agriculture and Natural Resources, 300 Lakeside Page 5 | December 2010 Page Drive, 6th Floor, Oakland CA 94612-3560, or call (510) 987-0096. Commissioner’s offi ce, http://www.cdpr.ca.gov/docs/county/comenu.htm.