Integrated Pest Management for Home Gardeners and Landscape Professionals

The elm , beetle has at least one generation a (=) luteola, is a leaf-chewing year in northern California and two pest of elm , especially European to three generations in central and elm . American and most Asian southern California. elm species are less severely fed upon. Most Chinese elm , , DAMAGE and many newer elm cultivars are Adults chew entirely through the leaf, infrequently fed upon. often in a shothole pattern. Larvae skeletonize the leaf surface, causing IDENTIFICATION damaged foliage to turn brown to Adults are 1/4 inch long, olive-green whitish (Figure 4). Elm leaf , Figure 1. Adult, eggs, and first-instar beetles with black, longitudinal stripes when abundant, can entirely defoli- of . along the margin and center of the back ate large elm trees, which eliminates (Figure 1). Females lay yellowish eggs summer shade and reduces the aes- in double rows of about 5 to 25 on the thetic value of trees. Repeated, exten- underside of . Eggs become gray- sive defoliation weakens , caus- ish before hatching. Larvae resemble ing trees to decline. However, the elm caterpillars and are black when newly leaf beetle has not been a significant, hatched and shortly after molting widespread problem in California (shedding the old skin). After feeding, since the 1990s. larvae become yellowish to green with rows of tiny dark tubercles (projec- MANAGEMENT tions). Third-instar larvae grow up to It is essential to correctly identify the Figure 2. Third-instar elm leaf beetle 1/3 inch long and have dense rows of cause of damaged elm leaves before larvae. dark tubercles down their sides that taking management action. European resemble two black stripes (Figure 2). flea , alni, also chews Pupae are orange to bright yellow. holes in elm leaves and causes elms to defoliate. This introduced beetle LIFE CYCLE has become a serious elm pest in the The elm leaf beetle develops through eastern United States, but currently four life stages: egg, larva, , and does not occur in California. Also adult (Figure 3). Adults commonly from a distance, foliage severely overwinter in bark crevices and wood- chewed by beetles resembles the piles or in buildings. In spring they fly browning and dieback caused by to elm foliage and chew leaves, and fungi, Ophiostoma females lay eggs. Eggs hatch into lar- (=Ceratocystis) ulmi and O. novo-ulmi. vae that develop through three instars Report any suspected Dutch elm dis- (growth stages) over a period of several ease, European flea weevil, or other Figure 3. Elm leaf beetle stages and life weeks while chewing on foliage and new pests to the local county agricul- cycle. then crawl down the trunk. Ma- tural commissioner. cides, bark banding, or systemic insec- ture larvae become curled and inactive (a stage referred to as prepupae), then Where the elm leaf beetle is a prob- ticide. Recognize that elm leaf beetle pupate, sometimes in large numbers, lem, manage it with an integrated populations historically have fluctu- around the tree base. After about 10 program that incorporates good ated dramatically from year to year and days as pupae, adults emerge and fly to cultural practices, conservation of trees do not warrant treatment most the canopy to feed and, during spring natural enemies, regular monitoring, years. When management is warranted, and summer, lay eggs. The elm leaf and the use of less-persistent insecti- use a combination of methods; because

PEST NOTES Publication 7403

Statewide Integrated Pest Management Program June 2014 June 2014 Elm Leaf Beetle no single action improves the health of Monitoring elm trees or kills 100% of the pests. Determine the need and effective timing for any pesticide application Cultural Control by visually inspecting leaves at about Good cultural care of trees is an essen- weekly intervals beginning in spring tial component of integrated pest man- when the first generation of eggs and agement. American and European elm larvae are expected. Watch for the species are adapted to summer rainfall. appearance of clusters of yellowish to Maintain tree vigor, and protect trunks gray eggs and caterpillar-like larvae. and roots from injury, by providing The calendar date of peak abundance appropriate irrigation in areas with and damage varies greatly from year summer drought. Check for dead or to year depending on spring tempera- dying branches and promptly remove tures. If beetles are too abundant, use Figure 4. Damage due to elm leaf beetle them. Dying branches pose a limb drop the heat accumulation method dis- feeding. (failure) hazard and provide habitat for cussed in Degree-Day Monitoring to bark beetles, multistriatus and determine the optimal time to inspect S. schevyrewi foliage and to accurately time insecti- , which vector the Dutch beetles are too abundant) apply insecti- elm disease fungi. Avoid unnecessary cide application. cide. Generally the higher the tempera- pruning; and when pruning make cuts ture, the sooner beetles and damage properly, preferably during late fall and If you plan to spray foliage or apply appear in the spring. When spring tem- winter and when trees are young. systemic insecticide to trunks, make the application when first- and second- peratures are cooler, elm leaf beetles appear later because they do not feed, Choose species or cultivars that resist instar (small) larvae are abundant. grow, or reproduce below a “threshold both Dutch elm disease and elm leaf With bark banding discussed below, temperature” of about 52°F. beetle when planting (Table 1). Pest- band as soon as third-instar (larger) resistant elms include Accolade, Emer- larvae are observed on leaves. To predict the peak abundance of each ald Sunshine, Frontier, Prospector, and elm leaf beetle life stage, temperatures most Chinese elms, except Dynasty. If you drench or inject soil with a root-absorbed, systemic insecticide, are monitored in units called degree- the most effective application time is days. One degree-day is 1 degree above Control Action Guidelines. Healthy spring when elm trees flush new leaves elm trees can tolerate substantial dam- the ’s lower threshold tempera- or shortly after leaf flush. The time for age to leaves; total defoliation may have ture maintained for a full day. For the action is before you know definitely little long-term effect on healthy elms, elm leaf beetle, degree-days above 52°F whether beetles will become abundant especially if leaf damage occurs late in are accumulated for each season begin- enough to warrant this preventive ap- the season. Suggested guidelines are ning March 1. The first- and second- plication. to take action when needed to prevent instar larvae of first-generation elm leaf greater than 40% defoliation (portion beetles are most abundant at about 700 Generally, insecticide application is degree-days above 52°F accumulated of leaf area chewed or leaves dropped unlikely to be warranted if: prematurely); or if damage is less toler- from March 1. If populations are high • beetles and damage were low during and damage is anticipated, foliar in- able or occurring earlier in the growing late summer the previous year; secticide spray or trunk spray or injec- season, a treatment threshold of 20% • systemic insecticide was properly tion of systemic insecticide at about defoliation may be used. For additional applied the previous growing 700 degree-days will catch susceptible information on how to predict the season; or larvae at their greatest abundance. amount of defoliation from each beetle • the winter was relatively warm or generation refer to the 1998 publication wet or both, because this weather by Dahlsten and others listed in Refer- apparently causes more “hibernat- Elm leaf beetle development can eas- ences. ing” beetles to die before elm leaves ily be predicted using the point-and- appear in spring. click, degree-day calculator online at Timing of action varies according to the If any of the above circumstances are http://www.ipm.ucanr.edu/calludt. control methods and situation. To avoid true, avoid insecticide application un- cgi/DDMODEL?MODEL=ELB&CROP unacceptable defoliation, when using less monitoring of reveals that =landscape. If you manage large num- methods that kill a smaller proportion elm leaf beetles are present and exces- bers of elms, you can further improve of the pests or take longer to provide sively abundant. your treatment by using degree-days control allowing beetles to continue to in combination with egg presence- feed and damage leaves, take action Degree-Day Monitoring. Monitor absence sampling, as explained in the sooner than you would when using temperatures to determine the opti- 1993 publication by Dahlsten and oth- faster-acting methods. mal time to inspect elm leaves and (if ers listed in References.

◆ 2 of 5 ◆ June 2014 Elm Leaf Beetle

Biological Control Monitor beetle abundance and dam- age, as discussed above, to determine Elm leaf beetle populations are usu- ally low at least partly because of treatment need, choice of method, and biological control by native predators timing. Apply insecticide only when and introduced parasites. Predators beetles are present or expected to be- of the elm leaf beetle include certain come too abundant. Insecticides can bugs, earwigs, lacewing larvae, and have unintended effects, such as con- predaceous ground beetles. The easiest taminating water, poisoning natural to recognize parasite is a small black enemies and pollinators, and causing tachinid fly, Erynniopsis antennata. After secondary pest outbreaks. Completely Erynniopsis larvae feed inside and read and follow the product label in- Figure 5. Elm leaf beetle prepupae kill beetle larvae, the parasite’s 1/5 structions for the safe and effective use (left) pupae, and pupae of the Erynniop- inch long, black to reddish pupae can of the insecticide. sis antennata parasite. be seen at the tree base among the yellowish, unparasitized beetle pupae Nonresidual, Contact Insecticides. (Figure 5). For more photographs of this Where elm foliage can be thoroughly beneficial fly, see the Natural Enemies sprayed, nonresidual, contact insecti- Gallery at www.ipm.ucanr.edu/PMG/ cides can provide control. These can be NE/elm_leaf_beetle_parasite.html. useful on small trees, to supplement bark banding (discussed below), during Adults of a tiny wasp, Oomyzus the first year of treatment and when gallerucae (Eulophidae), feed on elm leaf early-season beetle populations are beetle eggs; and the parasite’s larvae high. Products include azadirachtin feed inside eggs. The Oomyzus adult (AzaMax, Safer Brand BioNeem), neem Figure 6. Eggs from which elm leaf leaves a round hole when it emerges oil (Green Light Neem, Schultz Garden from beetle eggs, which remain golden. beetle larvae emerged are whitish. Eggs Safe Brand Neem), narrow-range oil from which Oomyzus gallerucae para- When unparasitized and a beetle larva (Bonide Horticultural Oil, Monterey has emerged, the egg shell is whitish sites emerged (center) are golden. Horticultural Oil), and pyrethrins, with a ragged hole (Figure 6). Another which many products combine with Bark Banding. Spraying a small area tiny eulophid wasp that kills beetle pu- piperonyl butoxide (Ace Flower & Veg- around the tree trunk with a residual, pae, Baryscapus brevistigma, leaves one etable Insect Spray, Garden Tech Worry contact insecticide kills larvae when or more small round holes in the pupae Free Brand Concentrate). they cross the treated bark and migrate and emerges from around the tree base. down after feeding in the canopy. Bark banding reduces damage by later beetle Conserve these parasites and preda- These insecticides have low toxicity to people and pets and relatively little generations by reducing the number of tors by avoiding foliar applications of elm leaf beetles that pupate and emerge residual (long-lasting), broad-spectrum adverse impact on pollinators and natural enemies. To obtain adequate as adults, especially when done to all insecticides. To obtain maximum ben- nearby elms. efits from biological control, minimize control, spray must thoroughly cover the underside of infested leaves; and pesticide application, use less-persis- Bark banding alone will not provide typically, foliage must be sprayed more tent products, or apply insecticide as a satisfactory control in many situations, than once per season. bark band in an integrated program. especially if only one or a few trees are treated. Expect good control dur- Short-Residual Insecticides. Spinosad Chemical Control ing the first season of bark banding on is foliar sprayed, absorbed short dis- Where elm leaf beetle damage is antici- Siberian elms (). When pated to be intolerable, chemical con- tances into tissue (it has trans- banding more susceptible species such trols include: laminar activity), and persists about 1 as English and Scotch elms, expect little • foliar spraying a nonresidual (non- week. It can be easier to obtain control or no control the first year if beetles are persistent) contact insecticide or a using spinosad in comparison with abundant during the first generation; short-residual, translaminar the products above. Spinosad (Captain banding all nearby elms for several insecticide Jack’s Deadbug Brew, Conserve, Mon- consecutive years can provide control • bark banding, spraying bark with a terey Garden Insect Spray) can be toxic after the first year of treatment. residual, contact insecticide to certain natural enemies (e.g., preda- • systemic insecticide, which can be tory mites, syrphid fly larvae) and To bark band spray a several feet wide applied various ways bees when sprayed and for about 1 day area encircling the trunk around A professional applicator must be hired afterward. Do not apply spinosad to the first main branch crotch. Carba- to use certain methods. plants that are flowering. ryl (Sevin) can be applied at the rate

◆ 3 of 5 ◆ June 2014 Elm Leaf Beetle

labeled for bark beetles (about 2% active Table 1. Elm (Ulmus) Tree Susceptibility to Dutch Elm Disease (DED) and Elm Leaf ingredient). Pyrethroids (e.g., fluvalin- Beetle (ELB). ate) labeled for application to bark also Tree Susceptibility provide control. Bark banding may Elm Common Name Scientific Name ELB DED need to be done by a licensed pesticide Emerald Sunshine Ulmus propinqua3 R R applicator, because effective products generally are not available for home Patriot (U. glabra X U. carpinifolia X R R users. Do not use products labeled only U. pumila) X U. wilsoniana for foliar application. The product will Prospector U. wilsoniana selection R R not be effective for trunk banding un- Frontier U. carpinifolia X U. parvifolia R MR less the label includes directions for 3 application to bark. Morton Accolade U. japonica X U. wilsoniana R MR American New U. americana selection R S Inspect foliage regularly and spray bark Horizon when mature larvae are first observed Homestead U. glabra X U. carpinifolia X U. pumila R S on leaves. For more accurate timing, Morton Glossy U. pumila X U. japonica X U.?3 R S accumulate degree-days and spray the Triumph trunk when about 700 degree-days New Horizon U. pumila X U. japonica3 R S (above 52°F) have accumulated from Morton Plainsman U. pumila X U. japonica3 R HS March 1. A single application of carba- Vanguard1 ryl to the bark each spring can kill most Morton Red Tip U. japonica X U. wilsoniana3 R HS larvae that crawl over it all season long. Danada Charm To determine if the bark band is still Morton Stalwart U. carpinifolia X U. pumila X U.?3 R HS effective, regularly inspect around the Commendation base of trees throughout the season. If Pioneer1 U. glabra X U. carpinifolia R HS many beetles have changed from green- American Valley U. americana selection MR R 1 ish prepupae (the stage killed by band- Forge ing) to yellowish pupae (unaffected Chinese2 U. parvifolia MR R beetles), a second application may be zelkova MR R warranted. Siberian U. pumila MR S Dynasty Chinese2 U. parvifolia selection MR HS Systemic Insecticides. Systemic in- secticides are absorbed by one plant American U. americana HS S part (e.g., trunks or roots) and moved English U. procera HS HS (translocated) to leaves or other plant Scotch U. glabra HS HS parts. In comparison with systemics KEY that are sprayed onto foliage, products HS = Highly susceptible labeled for soil drench or injection or for MR = Moderately resistant trunk injection or spraying minimize R = Resistant environmental contamination and may S = Susceptible ? = hybrid includes some uncertain or unknown elm parentage be more effective. Trunk application of systemic insecticide can provide rela- 1. Have exhibited poor growth structure and high pruning requirement when young and grown in tively rapid control. There is a longer California. 2. Dynasty is highly susceptible to ELB, most Chinese elms (e.g., Allee, Athena, Drake, Evergreen, time delay between soil application and and True Green) are resistant to elm leaf beetle. However, in coastal areas where elm anthracnose insecticide action. Most uses require is a serious problem, Brea and Drake cultivars can be good choices because they are resistant to elm anthracnose. hiring a professional pesticide applica- 3. Budded onto U. pumila rootstock, Scientific Name is for the scion (upper trunk and canopy). tor. Some home-use products can easily Source: McPherson et al. 2009. be drenched into soil around the tree trunk using the mix-and-pour method. acephate (Lilly Miller Ready-to-Use Systemics can translocate into flowers Systemic neonicotinoids include dinote- Systemic, Orthene) are other available and have adverse effects on natural furan (Safari) and imidacloprid (Bayer systemic insecticides. enemies and pollinators that feed on Advanced Tree & Shrub Insect Control, nectar and pollen. However, elms are Merit). Properly applied, one applica- Some systemic insecticides can cause wind pollinated and most elm species tion can provide season-long control. spider mite outbreaks. Foliar sprays of flower before leaves flush and before the The insect growth regulator abamectin them can be toxic to beneficial recommended times of insecticide ap- (Agri-Mek) and the organophosphate that contact spray or treated leaves. plication.

◆ 4 of 5 ◆ June 2014 Elm Leaf Beetle

Unless the product label directs other- Calif. Agric. Nat. Res. Also available Dreistadt, S. H., D. L. Dahlsten, D. L. wise, do not apply systemic insecticides online at http://californiaagriculture. Rowney, S. M. Tait, G. Y. Yokota, and to plants during flowering or shortly ucanr.edu. W. A. Copper. 1991. Treatment of de- before flowering, wait until after plants structive elm leaf beetle should be have completed their seasonal flower- Dahlsten, D. L., S. M. Tait, D. L. Rowney, timed by temperature monitoring. ing. With soil application, when pos- and B. J. Gingg. 1993. A monitoring sys- Calif. Agric. 45(2):23–25. Univ. Calif. sible, wait until nearby plants also have tem and developing ecologically sound A g r i c . N a t . R e s . A l s o a v a i l a b l e o n l i n e a t completed flowering as their roots may treatments for elm leaf beetle. J. Arbo- http://californiaagriculture.ucanr.edu. take up some of the soil-applied insec- riculture 19(4):181–186. Also available ticide. McPherson, G., L. Costello, J. Harding, online at http://joa.isa-arbor.com. S. Dreistadt, M. L. Flint, and S. Mezger. If applying systemic insecticide, use 2009. National elm trial: Initial report Dreistadt, S. H., J. K. Clark, and M. L. soil application or a trunk spray when- from Northern California. Western ever possible. It is difficult to repeatedly Flint. 2004. Pests of Landscape Trees and Arborist. Fall 2009:32–36. Also avail- place insecticide at the proper depth Shrubs: An Integrated Pest Management able online at http://www.fs.fed.us/ with systemic injection and implants, Guide. 2nd ed. Oakland: Univ. Calif. psw/programs/uesd/uep/products/ and these methods injure trees and can Agric. Nat. Res. Publ. 3359. CUFR_780_Elm_trials_2009.pdf. spread plant pathogens on contami- nated tools. When injecting or implant- AUTHORS: S. H. Dreistadt, UC IPM Program, University of California scientists and other ing multiple trees, before moving to UC Davis; and A. B. Lawson, Entomology, qualified professionals have anonymously peer California State University, Fresno. reviewed this publication for technical accuracy. work on each new tree, scrub any plant The ANR Associate Editor for Pest Management sap from tools or equipment that pen- managed this process. TECHNICAL EDITOR: M. L. Flint etrate trees and disinfect tools with a To simplify information, trade names of products EDITOR: K. Beverlin have been used. No endorsement of named products registered disinfectant (e.g., bleach). At is intended, nor is criticism implied of similar products least 1 to 2 minutes of disinfectant con- ILLUSTRATIONS: Figs. 1–2 and 4–6, J. that are not mentioned. This material is partially based upon work tact time between contaminated uses is K. Clark; Fig. 3, adult, first instar, second supported by the Extension Service, U.S. Department generally required. Consider rotating instar: L. O. Howard. 1895. The Shade- of Agriculture, under special project Section 3(d), work among several tools and use a tree Insect Problem in the Eastern United Integrated Pest Management. freshly disinfected tool while the most States. Yearbook of the USDA. Washington, D.C.; egg cluster, prepupa: F. Silvestri. recently used tools are being soaked in 1910. Bollettino del Laboratario di Zoologia Produced by UC Statewide disinfectant. Avoid methods that cause Generale e Agraria. Portici 4:246-289; Third Integrated Pest Management Program University of California, Davis, CA 95618-7774 large wounds, such as implants placed instar: John Muir Institute. 1979. The Elm Leaf in holes drilled in trunks. Do not im- Beetle. Berkeley, CA; Pupa: G. W. Herrick. plant or inject roots or trunks more 1913. Cornell Univ. Agric. Exp. Sta. Bull. 333. than once a year. This and other Pest Notes are available at www.ipm.ucanr.edu. Residual, Foliar Sprays. Foliar sprays of broad-spectrum insecticides with For more information, contact the University of residues that can persist for weeks are California Cooperative Extension office in your not recommended for elm leaf beetle county. See your telephone directory for addresses and phone numbers, or visit http://ucanr.org/ce.cfm. control. Products to avoid include carbamates (carbaryl or Sevin), nonsys- WARNING ON THE USE OF CHEMICALS Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations temic organophosphates (malathion), given on the container label. Store all chemicals in the original, labeled containers in a locked cabinet or shed, and pyrethroids (fluvalinate, perme- away from food or feeds, and out of the reach of children, unauthorized persons, pets, and livestock. thrin). These are highly toxic to natural Pesticides applied in your home and landscape can move and contaminate creeks, rivers, and oceans. Confine chemicals to the property being treated. Avoid drift onto neighboring properties, especially gardens enemies and pollinators and can cause containing fruits or vegetables ready to be picked. spider mite outbreaks. Because their Do not place containers containing pesticide in the trash or pour pesticides down the sink or toilet. Either use the pesticide according to the label, or take unwanted pesticides to a Household Hazardous Waste Collection use in landscapes and gardens can run site. Contact your county agricultural commissioner for additional information on safe container disposal and or wash off into storm drains and con- for the location of the Household Hazardous Waste Collection site nearest you. Dispose of empty containers taminate municipal wastewater, these by following label directions. Never reuse or burn the containers or dispose of them in such a manner that insecticides are being found in surface they may contaminate water supplies or natural waterways. water and are adversely affecting non- ANR NONDISCRIMINATION AND AFFIRMATIVE ACTION POLICY STATEMENT target, aquatic organisms. It is the policy of the University of California (UC) and the UC Division of Agriculture & Natural Resources not to engage in discrimination against or harassment of any person in any of its programs or activities (Complete nondiscrimination policy statement can be found at http://ucanr.edu/ REFERENCES sites/anrstaff/files/183099.pdf). Dahlsten, D. L., D. L. Rowney, and A. Inquiries regarding ANR’s nondiscrimination policies may be directed to Linda Marie Manton, B. Lawson. 1998. IPM helps control elm Affirmative Action Contact, University of California, Agriculture and Natural Resources, leaf beetle. Calif. Agric. 52(2):18–24. Univ. 2801 Second Street, Davis, CA 95618, (530) 750-1318.

◆ 5 of 5 ◆