REVIEW

pest-resistant plants in landscapes are simple and, in many cases, readily available approaches to reducing the dependence on chemical use. Research on effective, low-cost IPM methods is essential if chemical use in landscape management is to decrease. Current impediments to reducing the pollu- tion potential of chemicals used in the landscape include the limited number of easily implemented, reliable, and Review cost-effective alternative pest control methods; underfunding of research on development of alternative pest control measures; limited knowledge of commercial operators, chemical and nursery sales representatives, land- scape architects, and the general public concerning available alterna- Reducing the Pollution Potential of tives; reluctance of the nursery industry to produce, and of the Pesticides and Fertilizers in the landscape architects to specify the use of, pest-resistant plant materials; lack Environmental Horticulture of economic or regulatory incentive for professionals to implement Industry: II. Lawn Care and alternatives; inadequate funding for education on the benefits of decreased Landscape Management chemical use; and the necessity of changing consumer definition of 1 2 1 unacceptable plant damage. We need Joyce G. Latimer , S. Kristine Braman , Reuben B. Beverly , to teach homeowners and profession- Paul A. Thomas3, Jerry T. Walker4, Beverly Sparks5, als how to manage irrigation to optimize plant growth; use sound Ronald D. Oetting2, John M. Ruter6, Wojciech Florkowski7, IPM practices for reducing disease, weed, and problems; and Denise L. Olson2, Carol D. Robacker1, Melvin P. Garber8, minimize pollution hazards from fertilizers and pesticides. Orville M. Lindstrom1, and William G. Hudson9

Summary. Optimizing growing Additional index words. runoff, conditions and, thereby, plant growth he environmental horticul- surface water contamination, best reduces the susceptibility of plants to ture industry comprises management practices many disease and insect pest prob- T related commodities including lems. Educating lawn or landscape greenhouse, nursery, and turfgrass management professionals and crops, as well as the services associated The Ornamentals Working Group, Georgia Experiment homeowners about plant health with their use. According to estimates Station, The University of Georgia, Griffin, GA 30223. management reduces the need for from the USEPA, pesticide users in the This project received partial funding from the Pollution chemical intervention. Pesticides United States account for one-fourth Prevention Assistance Division of the Georgia Depart- combined with N and P fertilizers of the total active ingredients (a.i.) of ment of Natural Resources. contribute to water pollution prob- conventional pesticides used in the 1 lems in urban areas; thus, it is Horticulture. world—about 1.1 billion pounds a.i. 2 important to manage the amount, Entomology. (499 million kg) (Aspelin, 1994). 3 timing, and placement of chemicals Department of Horticulture, The University of Geor- and fertilizers. To educate consumers Herbicides are used in the greatest gia, Athens, GA 30602. amounts in the United States—620 4 applying pesticides and fertilizers in Plant pathology. residential gardens, we must educate million pounds a.i. (281 million kg)— 5Department of Entomology, The University of Georgia, the sales representatives and others followed by insecticides at 247 million Athens, GA 30602. who interact most closely with pounds a.i. (112 million kg), and fun- 6Department of Horticulture, Coastal Plain Experi- consumers. Evidence suggests that ment Station, The University of Georgia, Tifton, GA gicides at 131 million pounds a.i. (59.4 31793. knowledge about the effects of million kg) (Fig. 1a). Seventy-five per- chemicals is limited and that warning 7Agricultural and applied economics. cent of the total amount of pesticides labels are not read or are ignored. 8Department of Horticulture, Rural Development Cen- Integrated pest management (IPM) used in the United States is used in ter, The University of Georgia, Tifton, GA 31793. offers alternatives to conventional traditional agriculture (Fig. 1b). Eigh- 9Department of Entomology, Rural Development Cen- chemical treatments, but such teen percent of the pesticides in the ter, The University of Georgia, Tifton, GA 31793. methods are not used commonly United States is sold to industrial, com- The cost of publishing this paper was defrayed in part by because of their relatively high cost mercial, and government entities (in- the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertise- and their uncertain impact on pests. cluding commercial ornamental crop ment solely to indicate this fact. Pest detection methods and using producers and professional pest con-

222 HortTechnology ● July/Sept. 1996 6(3) trol operators), and 7% is sold to home garden activity with the highest level (Ward et al., 1993). and garden consumers. Only about of United States household participa- In addition to pest control by 25% of the total amount of pesticides tion and total spending, with an esti- homeowners, a large management in- sold in the United States is used for mated 52 million households spend- dustry maintains plants in the land- nonagricultural purposes. However, ing a total of $6.4 billion for lawn- scape. In 1993, lawn care and land- most nonagricultural applications are care-related products and equipment scape services were purchased by 11.1 in urban areas, thus increasing their (National Gardening Association, million United States households perceived impact. The agriculturally 1994). (16%) (National Gardening Associa- accepted concept of a risk to benefit The public’s increased horticul- tion, 1994), resulting in about $12.5 ratio is considered by many to be un- tural activity has resulted in more pes- billion spent on these services (Seed acceptable for pesticide use in urban ticide use. Nationwide, 27 million World, 1993). The number of areas. Since the benefits of high-qual- households reported using pesticides homeowners using professional land- ity ornamental plantings are difficult at least once during 1989 to control scape services increased 29% between to quantify, any risks associated with pests of their lawns, trees, and gardens 1992 and 1993 and was expected to pesticides in landscapes or lawns increase another 6% in 1994 may be deemed unacceptable (Seed World, 1993). Jobs and (Adamczyk, 1993). income generated by the land- This paper emphasizes scape management and lawn- methods to reduce potential pol- care industry represent a grow- lution from pesticides and fertil- ing contribution to local econo- izers applied during lawn care mies. According to Hubbard et and landscape management. The al. (1989, 1990), the number of first part summarizes the scope full- and part-time employees in and economic impact of this seg- landscape firms operating in the ment of the environmental hor- metro-Atlanta area in 1987 ex- ticulture industry. The next part ceeded 5300, with an annual describes the status of pesticide payroll of almost $42 million; and fertilizer use by consumers, metro-Atlanta lawn-care firms the potential for pollution from employed more than 5600 em- fertilizers, and the historical use ployees with an annual payroll of chemical pesticides in the man- of over $53 million. agement of lawns and landscapes. Status of pesticide and Current status of alternative pest control measures and the im- fertilizer use in urban pediments to reducing pesticide landscapes use in landscapes are detailed. Managed landscapes are We conclude with a summary of characterized by tremendous di- the impediments to reducing versity of plant material and as- potential pollution from pesti- sociated potential pests com- cides and fertilizers in urban land- pared to traditional agricultural scapes and a summary of man- monoculture situations. This agement and educational strate- degree of complexity confounds gies for reducing pollution in attempts to develop and imple- Fig. 1. (A) Distribution of types of pesticides environmental horticulture. used in the United States. (B) Distribution of ment integrated pest management major pesticide users in the United States; (IPM) strategies. Scope and economic impact commercial includes industrial and Many , weeds, and diseases of the lawn care and government entities, environmental commonly occur in lawns and orna- horticulture operations, and professional pest landscape management control operators (based on data of Aspelin, mental landscapes. Details of the biol- 1994). ogy, occurrence, and management of industry the most injurious turfgrass insects are Ornamental horticulture interacts reviewed by Tashiro (1987). Johnston with almost every homeowner and (Raupp et al., 1992). From 1989 to and Lyon (1988) provide a detailed consumer in the United States. More 1993, the total number of households review of the insect pests found on than 80% of the 93.3 million house- practicing insect control ranged from a landscape ornamentals. holds in the United States participates low of 23 million households in 1993 Pesticide and fertilizer use by in gardening activities (Behe and to a high of 37 million in 1990 (Na- consumers. Sixty-nine million of the Beckett, 1993). Consumer interest in tional Gardening Association, 1994). 94 million households use at least one gardening, landscaping, and hobby- A recent survey of Albuquerque, N.M., pesticide per year (Aspelin, 1994). In- greenhouse activities is increasing. In residents revealed that 90% of resi- secticides, primarily for structural and 1993, per capita spending by consum- dents had someone in the home who nuisance pests, account for the most ers on plant materials averaged $150 applied insecticides in their own land- active ingredient used in the home and (Johnson, 1993). Also, in 1993, lawn scapes, spending an average of $36.10 garden market, followed by herbicides, care continued to rank as the lawn and per year per household on pesticides fungicides (not including disinfec-

HortTechnology ● July/Sept. 1996 6(3) 223 REVIEW

tants), and others (rodenticides, fumi- Diego County, Calif., found that 10% least amount of experience in appro- gants, and molluscicides). of households had someone outside priate horticultural practices and safe Using results from the 1990 Na- the home applying their pesticides use of pesticides. Relatively few are in tional Home and Garden Pesticide (Pittenger and Lazaneo, 1989). Pre- a position to educate fellow gardeners. Use Survey (NHGPUS), Whitmore et liminary survey results of Albuquerque Less than 50% of the homeowners al. (1993) estimated that 90% of single- residents indicated that 8% of the resi- reads the pesticide label, and many family residences had at least one pes- dents have professional applicators ignore common safety procedures, par- ticide in storage in 1990 and 22% had apply pesticides to control landscape ticularly with regard to pesticide stor- more than five products in storage. pests (Ward et al., 1993). age (McEwen and Madder, 1986; Households treat for microorganisms Sixteen of the states surveyed in Whitmore et al., 1993). Six percent of (mildew, mold, bacteria, and virus, the 1990 NHGPUS require direct all households in the NHGPUS had 47%), ants (36%), mosquitoes (28%), notification or posting of pesticides pesticides in storage because they did cockroaches (24%), and fleas (24%). used by commercial lawn care and not know how to dispose of them Only 14% of households treat for in- landscape management companies properly (Whitmore et al., 1993). sect pests in lawns, ornamentals, or (Whitmore et al., 1992). Fifty-seven A 1981 survey of Virginia garden. Weeds also were treated by percent of households using the ser- homeowners’ preferences in lawn care about 14% of households. vices of lawn care companies in these revealed that 63% rated their lawns as The 1993–94 National Garden- states reported that they were informed average, but 70% was not satisfied with ing Survey (NGS) reported that 54% of the chemicals used and advised of the current condition of the lawn (Rob- of all United States households, or 52 safety precautions. However, only 35% inson, 1985). Most (95%) of the million households, participated in do- of those using landscape service com- homeowners thought that well-kept it-yourself lawn care in 1993, spend- panies were informed of the chemicals lawn and shrubs increased the dollar ing an average of $130 per household used. In states where notification is value of their homes, and 75% of the (National Gardening Association, not required by law, only 38% of house- homeowners was willing to pay up to 1994). Twenty-four percent of house- holds using lawn care services were $100 per year for lawn care. The sur- holds landscaped in 1993, spending an informed of the chemicals used. EPA vey further revealed that most average of $250 per household. In currently is circulating draft guidelines homeowners did not know what pri- addition, 28% and 21% of households for national posting requirements for mary pests were present in their lawns participated in shrub and tree care, commercial pesticide applicators, or what control methods were recom- respectively. Fifty-six percent of United which also may include a call for volun- mended for pests. Eighty-five percent States households purchased outdoor tary posting by homeowners applying said that insect pests were not causing fertilizers, insect controls, or chemi- pesticides to their own landscapes damage to their lawns, and a similar cals. The most common do-it-yourself (Nursery Manager, 1994). Connecti- percentage did not apply insecticides products purchased for lawn and gar- cut already requires homeowners and to their lawns yearly. Asked to identify den activities included weed and feed professional applicators to post chemi- their lawn problems, 43% cited poor fertilizer (28% of households), ready- cals used, but enforcement is limited soil conditions (fertility, pH), 30% cited to-use insect control spray (22%), dry by resources (Adamczyk, 1993). water availability, and 3% cited insect or granular chemical fertilizer (17%), Consumer education regarding and disease pests. The survey author liquid or water-soluble fertilizer (15%), the safe and proper use of pesticides suggested that Virginia residents may and ready-to-use or concentrated her- and fertilizers is necessary to reduce be amenable to implementing an IPM bicide (13%). Natural or less-toxic in- the potential for pollution. A recent program because they are not predis- sect control products were purchased analysis of American gardeners by level posed to depend on pesticides for in- by only 6% of the households. Natural of activity, participation, and sophisti- sect control, and cultural and fertilizers also were purchased by some cation revealed that 61% could be con- nonchemical remedies are more ap- households; blended all-natural or or- sidered dabblers—those who are be- propriate for the problems they identi- ganic fertilizers were purchased by 8%; ginners, have minimal training or ex- fied. blood meal, bone meal, and rock pow- perience, and spend 2 h per week or Results of a homeowner survey in ders by 6%; and manure by 11% of less at gardening (B. Behe, personal Albuquerque indicated that 17% of households. communication, 1993). Nineteen per- the homeowners received their pest Almost 15% of households with a cent are decorators—those who own control information from nursery sales private lawn in the 1990 NHGPUS their own home, spend 5 h per week in people, 14% from friends and relatives, had pesticides applied by someone gardening activities, and are functional 13% from university, extension, or other than a member of the house- gardeners. Eighteen percent of the Master Gardener sources, 13% from hold, generally by a commercial lawn gardeners are cultivators—those with the pesticide labels, 12% from books, care company (Whitmore et al., 1993). 17+ years experience and spend 10 h 10% from newspapers and magazines, The 1993–94 NGS reported that 16% per week in gardening activities. Fi- 8% from pest control or landscape of households purchased the services nally, only 3% are masters—those with professionals, 6% from television or of lawn care or landscaping profession- 20+ years experience, who spend an radio, and 5% from garden clubs (Ward als, 12% of the households purchased average of 26 h per week gardening, et al., 1993). However, the home- lawn care service, and 6% purchased and have an average of seven people owners were not confident in the in- landscape management services (Na- soliciting their advice on gardening. formation they received from sales rep- tional Gardening Association, 1994). These survey results indicate that most resentatives. Highest confidence rat- Surveys of specific areas, such as San garden-product consumers have the ings were given for information from

224 HortTechnology ● July/Sept. 1996 6(3) university or Master Gardener sources become available for plant use , this izer limits the likelihood of leaching, if or the pesticide labels. organic N must be mineralized to in- the amount of ammonia volatilization A Univ. of California (UC) study organic forms. Urea is rapidly hydro- is excessive, urea application would found that 22% of the people surveyed lyzed to the ammoniacal form after not be appropriate in terms of eco- received their pest control informa- application. Ammoniacal N, either nomics or resource management. tion from nurseries, because they were applied directly or formed from urea, Rather, the key will be to enhance convenient and easy to use, whereas is subject to volatilization loss as gas- efficient plant use of appropriate forms only 2% received information from eous ammonia. Alternatively, ammo- of N fertilizer. UC Extension Service (Pittenger and niacal N, which is relatively soluble, Landscapes are typically peren- Lazaneo, 1989). The UC and New can move through the soil profile in nial and densely populated with vari- Mexico sources indicated that educa- solution or be assimilated by plant ous plant species that tend to reduce tional activities should be focused on roots or microbes. Being positively pollution potential. Grasses, as well as professionals in sales, so they may ex- charged, ammoniacal N also is ad- herbaceous and woody perennials, tend that information to the general sorbed by soil particles by cation ex- develop extensive root systems over public. change. time, thus ensuring rapid recovery and Potential for pollution from In well-aerated soil under favor- assimilation of available N. Further- fertilizers in urban landscapes. able temperatures, ammoniacal N is more, the plant litter that accumulates Several authors have discussed research converted rapidly by soil bacteria to in perennial landscapes (leaf litter and on the potential for nonpoint source the nitrate form by nitrification. Ni- thatch) provides a relatively stable pollution by nutrients applied to land- trate thus formed, or applied directly source of N, which can be recycled scapes, particularly turf areas (Gold et as fertilizer, is negatively charged and slowly through the system. Likewise, al., 1990; Gold and Groffman, 1993; not retained by cation exchange. Ni- the stable soil–plant systems allow de- Gross et al., 1990; Harrison, 1992; trate is also quite soluble and moves velopment of large microbial popula- Morton et al., 1988; Petrovic, 1990). readily in the soil solution. When ex- tions, further ensuring efficient scav- A nutrient applied to a landscape cess water moves through the soil pro- enging of N not quickly taken up by becomes a pollutant when it moves file, nitrate can be leached readily from higher plants. As long as the soil is well from the root zone, generally, the top the root zone, thus becoming a poten- aerated and the landscape species are 20 cm (8 inches) of soil, into a water tial pollutant. Alternatively, in warm, healthy and appropriately irrigated and body. Nutrients reach surface waters poorly aerated soil, which occurs after fertilized, N leaching should be mini- either in solution or in suspension heavy irrigation or rainfall, soil bacte- mized. attached to soil particles in runoff wa- ria can use nitrate in the place of oxy- A notable exception to this opti- ter. To reach groundwater, nutrients gen in their respiration processes, re- mistic view is soil of perennial systems, must leach in percolating water drain- sulting in volatile losses of nitrous ox- in which stable large pores, as from ing below the root zone. Soil P is ides due to denitrification. Finally, free root channels and worm or insect tun- relatively insoluble, so its potential for nitrate, as with ammonium, can be nels, can develop. These biopores pro- nonpoint source pollution generally taken up by plant roots or be assimi- vide channels for rapid movement of depends on physical movement to sur- lated by soil microbes and thus immo- excess water through the soil profile face waters in association with eroded bilized or rendered unavailable for plant and out of the root zone, possibly soil particles; such erosion usually is use until the death and decomposition resulting in some localized loss of N limited from well-maintained land- of the microbial biomass. from the soil–plant system. This effect scapes (Gross et al., 1990; Harrison, Relatively little N leaches from has been noted in agricultural systems 1992; Harrison et al., 1993). Although well-managed turf areas, and nitrate- under conditions of reduced tillage P runoff amounts from turf areas may N concentrations reported in leachates (McCracken et al., 1995), although be higher than amounts reported in are well below the 10 mg·liter–1 stan- reduced tillage did not increase nitrate the literature due to excessive soil com- dard for drinking water established by leaching consistently. paction in high-traffic areas, which re- EPA (Gold et al., 1990; Gold and In summary, the overall nature of duces water infiltration (Harrison et Groffman, 1993; Gross et al., 1990; the landscape system should mitigate al., 1993), the probability that P ap- Morton et al., 1988). However, these against nonpoint source pollution by plied to landscapes will pollute surface studies must be examined critically: applied N and other fertilizers. Keep- waters seems small for most situations. the authors applied N as urea to estab- ing available N in the root zone re- In contrast to P, the solubility, lished turf but did not determine losses quires proper management of fertil- mobility, and potential loss of N from due to ammonia volatilization. The izer form, amount, timing, and place- the landscape depends on many com- low amounts of N leached in these ment, as well as good irrigation man- plex transformations (Petrovic, 1990). studies may have been due to N vola- agement. The potential nonpoint Nitrogen can be applied to the land- tilization losses. In other studies re- source pollution from landscape fer- scape in various chemical forms such as viewed by Petrovic (1990), more N tilization depends on the movement urea, ammoniacal, and nitrate forms; leached below the root zone when turf of water through the soil profile at in organic forms such as peat, lawn was fertilized with the nitrate form times when the soil solution contains waste, and sludge; or as combinations than when urea was applied. Thus, the soluble N. Thus, soil water relations of these forms. In addition, most of potential for N to leach from land- may have as much to do with potential the N resident in the soil profile is in scapes is greater than might be inferred fertilizer pollution as nutrient man- organic form in living or dead plant, from some studies, if soluble N forms agement itself. Indeed, Morton et al. , and microbial biomass. To are applied. Although using urea fertil- (1988) showed that overwatering fer-

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tilized lawns increased N loss, but well- advantage of long residual effective- Recent surveys have determined managed irrigation, even with high N ness of these chemicals was outweighed amounts of pesticide used in produc- application, did not result in higher N by increased insect resistance (Reinert, tion of sod, greenhouse, and nursery loss than from nonfertilized controls. 1982; Tashiro, 1982) and environ- plants (Oetting and Allison, 1994). Appropriate irrigation management in mental concerns, which resulted in However, few studies have examined landscapes is important for providing cancellation of cyclodiene registrations. pesticide use patterns in the landscape. proper nutrients for vigorous plant Organophosphates (e.g., chlorpyrifos, Neely et al. (1984) provided question- growth and in preventing nonpoint diazinon, trichlorfon, isazophos, and naires on fungicide and insecticide us- source pollution. Improving irrigation ethoprop) and carbamates (bendiocarb age to 529 commercial and 40 munici- efficiency requires knowledge of the and carbaryl) gained more widespread pal arborists in Illinois during 1982; moisture retention of the root me- use during the 1970s and 1980s. Syn- 156 arborists responded. The respon- dium to apply water to maintain, but thetic pyrethroids such as fluvalinate dents purchased a combined volume not exceed, that retention capacity. and cyfluthrin have been labelled more of 41,768 kg (9200 pounds) of fungi- Since relatively few residential land- recently for use in the landscape. cide and 1,021,500 kg (225,000 scapes are provided with in- pounds) of insecticide in 1982. stalled irrigation, education on Benomyl, maneb, and zineb water application methods and were the most frequently used soil water management is a criti- fungicides, whereas carbaryl, cal need. Water management as dimethoate, malathion, and a pollution prevention strategy dormant oil were the most fre- would require substantial edu- quently used insecticides. Scab cation of landscape managers and rust were the primary dis- and homeowners, but would eases. Scales, aphids, and bag- serve the dual purpose of con- worms were the most prevalent serving water by preventing its insect pests. Most of the tree wasteful application and pro- species common in residential tecting water quality by reduc- areas were sprayed for one or ing runoff and leaching of plant more pest problems. nutrients. Several studies document Historical aspects of a reduction in pesticide use fol- landscape pest management. lowing implementation of IPM Insect pests have been man- in landscapes. Holmes and aged primarily by conventional Davidson (1984) reported a chemical insecticides. Use of a 94% reduction in volume of pesticide is often the only prac- pesticide used when 11,000 tical means of preventing unac- plants on 26 client properties in ceptable damage to turf or ame- Maryland were transferred from nity plants from heavy or unex- the previous three cover sprays pected pest infestations. Effi- per year to a system of biweekly cacy of commercially available plant monitoring with spot- and experimental compounds spraying as necessary. Results is being evaluated constantly of other studies found a reduc- (e.g., Mizell and Schiffauer, tion in pesticide use often ex- 1987; Niemczyk, 1987). ceeding 70% of pre-IPM levels Historically, the gypsy (Coffelt and Schultz, 1990; eradication campaign in Funk, 1988; Sherald and Massachusetts between 1891 DiSalvo, 1987; Smith and and 1900 is reported as the first major Fig. 2. A Lindgren funnel—a pheromone Raupp, 1986). attempt to manage a landscape pest trap used to monitor or collect bark beetles— Status of alternatives to (Raupp et al., 1992). This campaign aids in determining when, or if, chemical led to the development of lead arsen- intervention is necessary. (Photo courtesy of conventional pesticides in ate as an insecticide, the use of which Whitney Cranshaw and Tom Eckburg.) urban landscapes continued for another 50 years. Spray- The development of IPM for the ing with other inorganic and botanical Heavy reliance on insecticides in landscape for the most part has paral- insecticides was common until the agricultural systems has resulted in sev- leled that for agriculture, but it is char- development of synthetic organic in- eral pests’ developing resistance to these acterized by some noteworthy special secticides after World War II. The chemicals. Although the magnitude of challenges. As outlined by Potter highly effective cyclodiene insecticides resistance problems in the landscape is (1993) for turfgrass IPM, the accep- (chlordane, dieldrin, aldrin, and hep- not known, a recent review suggests tance and implementation of IPM for tachlor) were used very effectively to that at least 36 insect and mite pests of the landscape is more difficult than for control insect pests in the landscape landscape plants are resistant to at least agricultural crops because of the 1) during the 1950s and 1960s (Potter one kind of insecticide (Raupp et al., perennial nature of the system, 2) and Braman, 1991). However, the 1992). greater heterogeneity of plants and

226 HortTechnology ● July/Sept. 1996 6(3) uses and the diversity of clientele, 3) Nielsen, 1984), flatheaded appletree able, damage or defoliation that ex- high aesthetic standards, 4) lack of borer (Potter et al., 1988), bagworm ceeds 10% (Raupp et al., 1989a). sampling methodology and decision- (Neal et al., 1987), obscure scale (Pot- Coffelt and Schultz (1990) determined making guidelines, and 5) lack of reli- ter et al., 1989), and others. Unfortu- that defoliation by orangestriped oak able, cost-effective alternatives to pes- nately, the value of these sampling worms that exceeded 10% was not ticides. Despite these limitations to tactics is limited, because few popula- acceptable to most homeowners. Vigor adoption of IPM strategies, consider- tion thresholds are defined for the of the trees as measured by starch able progress has reserves was not af- been made in de- fected, however, veloping alterna- until defoliation tive strategies to levels approached traditional chemi- 25%. By delaying cal control efforts. intervention until Pest detec- an aesthetic thresh- tion. In existing old of 25% was landscape IPM reached, significant programs, moni- reductions in pesti- toring provides cide use and real information on cost savings were the temporal and achieved. spatial abundance Cultural of pests and natu- tactics. Cultural ral enemies to in- practices, such as dicate the most fertilization, irriga- effective timing tion, mowing, and and placement of topdressing, may control tactics. affect pest abun- Monitoring tech- dance or the expres- niques used in sion of injury or dis- IPM programs in- ease. Little research clude visual in- has addressed the spection of plant material. Indicators Fig. 3. Chilocorus kuwanae, (a) adult and response of insect pests to the many (b) larva, is a predator that effectively of insect abundance such as frass also reduces populations of the euonymous scale. cultural factors that could be modified have been used to monitor for insects. (Photo courtesy of USDA.) to reduce infestation. To reduce herbi- Pheromones have cide use for weed been identified control in turf- and used for traps grasses, research in to detect and sur- cultural methods vey gypsy that decrease weed (Reardon et al., populations will be 1987), clearwing increasingly impor- borers (Neal and tant. Eichlen, 1983), Improper tip moths placement of orna- (Gargiullo et al., mental plants in 1983), Japanese landscapes can pro- beetles foundly affect their (Tumlinson et al., susceptibility to 1977), and cer- pests and plant es- tain lawn moths tablishment suc- (Clark and cess. Understory Haynes, 1990) species such as dog- (Fig. 2). Forecast- woods and azaleas, ing models based for example, are on heat-unit ac- vastly more prone cumulations have to infestation and been developed damage by dog- for a number of wood borer and turf and ornamental pests including vulnerable or damage-inducing stages azalea lace bug, respectively, when masked chafers (Potter, 1981), azalea of important pests. grown in full sun than shade (Potter lace bug (Braman et al., 1992), elm Studies of ornamental plants have and Timmons, 1983a; Raupp, 1984; leaf beetle (Driestadt and Dahlsten, revealed a general pattern that the Trumbule and Denno, 1995). Drought 1990), bronze birch borer (Akers and public perceives, and finds unaccept- renders many plants susceptible to at-

HortTechnology ● July/Sept. 1996 6(3) 227 REVIEW

tack by mites and borers, to certain introduced for classical biological con- directed. Miller (1989) reviewed the disease-causing fungi, and to white trol in California. Raupp et al. (1992) use of insecticidal soaps and oils on grubs in turf (Mattson and Haack, discuss control successes for insect pests amenity plants. These materials are 1987; Potter and Gordon, 1984). that attack landscape plants in various particularly effective against soft-bod- Mechanical methods are useful in locations around the world. They re- ied, sucking pests including aphids, managing several landscape pests. port that, in many cases, beneficial adelgids, and scale crawlers. Improved Sticky traps, banding, and pruning can insects were imported to control pests formulations of azadirachtin with very remove pests from trees or shrubs. in agricultural settings and subse- low mammalian toxicity have received Care to prevent wounding landscape quently made the transition to con- expanded registrations and are now trees substantially reduces problems trolling pests in urban environments. available for use on turf and ornamen- with borers and plant pathogens (Pot- Most of the successes involved hy- tals. Synthetic insect growth regula- ter and Timmons, 1983b). menopteran parasitoids controlling tors with novel chemistry are currently Host-plant resistance. An in- scale insect pests. However, predatory in development. They show excellent creased number of turfgrass cultivars insects also have been effective. For activity against soil-dwelling and fo- and ornamental plants with improved example, the imported coccinellid liar-feeding pests in turfgrass. disease resistance are currently avail- Chilocorus kuwanae has become es- Two strains of the Bt pathogen able. Endophyte-enhanced cool-sea- tablished (Fig. 3) and has reduced have registration for use against more son turfgrass cultivars offer some pro- populations of the scale Unaspis than 20 species of defoliating caterpil- tection from insect pests as well (e.g., euonymi effectively (Drea and Carlson, lars that may affect ornamentals (Raupp Siegel et al., 1989). A large range in 1987). et al., 1992). Conventional Bt formu- susceptibility among plant species and Managed landscapes contain a rich lations also are labelled for turf cater- cultivars to insects and disease-causing diversity of beneficial , as pillars, but they are not used widely in pests has been documented for euony- evidenced by the fauna reported in the industry because their performance mus to euonymus scale, crape myrtle maintained turfgrasses (Cockfield and is often erratic (Potter, 1993). New to crape myrtle aphid and powdery Potter, 1984; Braman and Pendley, strains of Bt have been discovered that mildew, azaleas to azalea lace bug, 1993a, 1993b). A 3-year study in have activity against mites, flies, and junipers to bagworm, ornamental trees Maryland revealed the presence of 28 beetles, offering great potential for use to Japanese beetle, cotoneaster and species of predaceous coccinellid in landscape pest management. pyracantha to hawthorn lace bug and beetles in nurseries (Staines et al., Nematodes (round worms) offer fireblight, and many other ornamental 1990). The need for conservation of advantages in pest control that include plant–pest combinations (Raupp et al., existing natural enemies has been dem- their lack of mammalian toxicity, com- 1992; Smith-Fiola, 1995). Greater col- onstrated by outbreaks of nontarget patibility with conventional spray laboration among plant pathologists, pests after applying pesticides. Scale equipment, effectiveness on a broad entomologists, and plant breeders of- insects, one of the most problematic array of pests, relatively quick kill, and fers the potential for landscape pest woody plant pests, often have large potential for commercial production management based on plant resistance parasitoid complexes. The influence of (Potter, 1993). Nematodes have been and reduced pesticide use, without these natural enemies may not be real- used successfully to control clearwing sacrificing plant quality. Reluctance of ized fully, however, because their ac- moth larvae in several tree species (Pot- the nursery industry to increase pro- tivity tends to peak during the period ter and Timmons, 1983a, 1983b), duction of pest-resistant plant materi- of greatest scale crawler activity. This black vine weevil larvae in potted nurs- als and the failure of landscape archi- developmental period is the time most ery stock (Stimmann et al., 1985), and tects to recommend their use are cited often recommended for insecticide the turfgrass pests white grubs, cut- as primary obstacles to more wide- control to target the crawlers, because worms, sod webworms, billbugs, and spread adoption of resistant plants for this stage is the most vulnerable devel- mole crickets (Potter and Braman, the landscape (Raupp et al., 1992). opmental stage of scale insect pests. 1991). Steinernema carpocapsae, the Landscape architects influence the Research aimed at determining com- component of most currently mar- choice of landscape materials (Garber, patibility of various management strat- keted nematode formulations, has low 1993) and are an appropriate target egies is needed. mobility and poor host-finding capa- audience for educational efforts con- Insecticides. Microbial, botani- bility in soil. Other nematode species cerning the use of pest-resistant plants. cally derived, and other products re- currently are being researched, and Biological control. Biological ported to be environmentally benign improvements in cultural and storage control of urban pest problems has a that have been successfully used in techniques will lead to enhanced effec- broad appeal to management profes- landscape pest management include tiveness and greater use in future IPM sionals and their clients because of the dormant and summer oils, azadirachtin programs. apparent ecological and environmen- (neem oil), insecticidal soaps, Bacillus Relatively few insecticides and tal safeness of such an approach. Clas- thuringiensis (Bt), and entomogenous acaricides are registered for use on sical biological control, conservation nematodes. Neely and Smith (1991) ornamentals (Mizell et al., 1991) and efforts, and augmentation have been reported that almost 50% of arborists turf. Those that are still available should attempted in landscape settings with surveyed used summer oil sprays, soaps, be managed carefully to maintain their varying degrees of success. Dreistadt and Bt. Highly refined summer oils effectiveness and to protect workers et al. (1994) list 19 woody landscape that are now available are very effective and the environment. The current pests that are reported to be substan- for many ornamental plant pests and trend in application of chemical pesti- tially controlled by natural enemies are safe for plants when applied as cides in landscape management is to-

228 HortTechnology ● July/Sept. 1996 6(3) ward those materials that have very change the public’s tolerance of control can be replaced with more low use rates and low mammalian tox- nondamaging levels of pests and will- environmentally friendly alternatives. icity compared to traditional products. ingness to pay for alternative methods The limited experience of Advances in application technology, of pest control are needed. Generally, homeowners in pesticide use provides such as subsurface application of insec- landscape management and lawn care a great opportunity to educate these ticides for turf, allow for placement of firms, competing among themselves people on alternative insect and dis- insecticides in the root zone where and pressured by customer demands, ease control measures. Educating pro- insects are feeding, reduce surface ex- apply pesticides following a prescribed fessional lawn or landscape manage- posure, and in some cases allow lower regimen, only occasionally using meth- ment operators and homeowners on use rates. ods that minimize the use of chemi- the concept of plant health manage- In summary, significant progress cals. Customers purchasing manage- ment would reduce the need for chemi- has been made in developing compo- ment services have limited understand- cal intervention. nents of and, to a lesser extent, in ing of scouting-based diagnosis and its Developing regional manuals for implementing IPM for turfgrass and relationship to the judicious use of plant health management and holding landscape plants. The advances in re- pesticides. Combined educational ef- workshops in nurseries, greenhouses, search on nematodes, environmentally forts by industry and university profes- and other large sales outlets for plant benign insecticides, microbial insecti- sionals will be required to modify pub- and pesticide products, such as Home cides, systemic fungicides, and host- lic expectation about what constitutes Depot or Wal-Mart, would target the plant resistance provide an encourag- responsible service as well as quality consumers needing the information. ing framework for developing sound landscapes. A large percentage of the lawn and management strategies. Somewhat less Additional constraints include the landscape management operators in progress has been made in using preda- lack of knowledge concerning the bi- the Atlanta survey and homeowners in tors and parasitoids as control tactics; ology and ecology of many prominent the New Mexico and California sur- developing simple, cost-effective and pest species and their associated veys indicated that they obtained their noninvasive sampling tactics; and in- beneficials as well as the impact of pest control information from sales dustry education. However, Raupp et weather on specific diseases of orna- representatives. Sales representatives al. (1992) emphasize that, during the mentals. More than half (57% to 70%) are a potential audience for educa- past 2 decades, at least 11 IPM pro- of the respondents to a metro-Atlanta tional efforts aimed at promoting envi- grams have been implemented for survey identified the following factors ronmentally friendly application of woody plants in nurseries or urban as limiting the implementation of IPM pesticides. Information on structural settings. The authors note that these in lawn care and landscape manage- and nuisance pests should be included, programs were sponsored largely by ment: information about pest biology since these are the pests most com- universities, although several coopera- is lacking; alternatives to traditional monly treated by consumers. tive efforts among universities, mu- chemicals are undetermined, costly, or Impediments to reducing po- nicipalities, institutions, state and fed- ineffective; and IPM practices are too tential pollution in environmen- eral agencies, and private enterprise time-consuming or are not well re- tal horticulture. Impediments to re- were noted. Nine of the studies re- ceived by clients (S.K. Braman, per- ducing the potential for environmen- ported a reduction in pesticide use sonal communication). One com- tal pollution with respect to the use of associated with the implementation of monly identified impediment, from conventional pesticides in the orna- IPM. In some cases costs declined, but this limited list, was a lack of available mental horticulture industry include in others costs increased. Adoption of information about pest biology. the following: IPM strategies has emerged primarily The complex interactions that 1) Inadequate pest sampling meth- in tree-care firms in the northeastern exist in diverse landscapes currently ods; sampling approaches devel- United States and in California. Sur- are poorly understood. Difficulty in oped for use in agronomic sys- veys indicate that those who receive predicting the occurrence and severity tems are not directly applicable formal IPM training are more likely to of pest outbreaks limits proactive man- to managed landscape settings adopt IPM practices (Raupp et al., agement tactics. The current lack of because of the aesthetic nature 1989b). reliable and cost-effective alternatives of the managed resource, its di- Impediments to reduced constrain managers to use effective, versity and heterogeneity, and inexpensive, and more-reliable man- because existing sampling meth- pesticide use in landscapes agement choices, which are usually ods are cumbersome, destruc- While prospects for the imple- conventional insecticides. tive, and time-consuming. mentation of IPM on a broad scale are 2) The reluctance of the nursery good, limitations must be addressed. Conclusions industry to produce, and of the Concerns over potential risks to hu- This paper has summarized the landscape architects to recom- man health and the environment have chemical and alternative control meth- mend, pest-resistant plant mate- led to public demand for critical reas- ods currently available, as well as those rials, which reduces the availabil- sessment of current management tac- that have potential for adoption for ity and widespread adoption of tics, but have in no way lessened the insect and disease control in the lawn- these materials in the landscape. demand that translates into high aes- care and landscape management in- 3) The nonavailability of easily thetic standards for urban landscapes dustry. Technical and fundamental implemented, reliable and cost- and recreational turf. Research and problems must be overcome before effective pest management alter- educational efforts that assess and the industry’s reliance on chemical pest natives and insufficient research

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