Sod Farms Research Articles

Pest Status of Invasive Crane Flies in New York Turfgrass and the Repercussions for Regional Plant Protection

Gauging the pest status of invasive insects is a vital element of postestablishment management and response plans. After their 2004 detection in New York, diverse field observations were summarized to appraise the pest status of Tipula oleracea L. and T. paludosa Meigen in turfgrass of the Northeast United States. In residential lawns, impacts included nuisance swarms of adults and accumulations of larvae, and stand loss because of thinning and die-back, mostly attributed to T. paludosa. No damage was attributed to early instars in fall despite densities of 123–544 larvae/m2. For late instars in spring, nondamaging and damaging densities were 123–142 and 753–829 larvae/m2, respectively. In golf courses, impacts included chewing damage on putting greens, nuisance accumulations of larvae on playing surfaces, die-back of rough-mown turf, and disruption resulting from vertebrate predation. Damage to putting greens was attributed to T. oleracea at densities of 140–318 larvae/m2. Abrupt appearance of injury and decline in abundance toward the center of infested greens was evidence for immigration from surrounding turf. Insecticidal control disrupted play because of the abundance of larval cadavers on the surface. On roughs, T. paludosa caused die-back as a consequence of root pruning. For early instars in fall and late instars in spring, nondamaging densities were 136–375 and 77–115 larvae/m2, respectively. In sod farms, impact included presence of larvae in production fields and the first confirmation that harvesting, shipping, and installing infested sod can lead to establishments at sites remote to field of origin. The categories and magnitude of damage observed in New York, the new insecticide burden this engenders, and the likelihood of spread to new regions and agroecosystems, indicate that continued range expansion will have serious repercussions for regional plant protection.

Characterizing Weed Populations in Different Turfgrass Sites throughout the Klang Valley of Western Peninsular Malaysia

A field survey was conducted in 2007 to characterize weed populations in different turfgrass sites throughout the Klang Valley of western Peninsular Malaysia. Sites included golf course putting greens, athletic fields, sod farms, and residential lawns. Weeds present in each site were identified and the data were used to calculate frequency, distribution uniformity, density, relative abundance, and community coefficient values for each species. Seventy-nine weed species, belonging to 16 families, were found. The most species were found on residential lawns, and the fewest were found on golf course putting greens; athletic fields and sod farms ranked intermediately. A total of 19 different weed species were classified as major (relative abundance ≥ 15), and abundance rankings varied by turfgrass area. Greater kyllinga had the highest relative abundance values on athletic fields (45.5) and golf course putting greens (71.5), and the second highest value (21.7) on residential lawns. Forked fringerush and annual sedge had the greatest relative abundance values on residential lawns and sod farms, respectively. Cogongrass was reported on 15% of the residential lawns evaluated. The heterogeneity of weed species composition suggests that control strategies will vary by turfgrass use area. Quantifying weed population dynamics will help researchers delineate integrated weed management strategies to turfgrass managers in Malaysia.

Quantification and Implications of Soil Losses from Commercial Sod Production

Commercial sod farms occupy about 1.62 × 103 km2 of the landscape of the United States. Land managers generally consider sod farms on an equal footing with other, sustainable agricultural land uses. We measured soil losses associated with sod harvesting in farms in the northeastern United States. Sod harvest resulted in soil losses ranging from 74 to 114 Mg ha−1 yr−1, considerably higher than the tolerable soil loss of 6.7 Mg ha−1 yr−1 Soil losses were proportional to time under sod production, with soil removal rates of 0.833 cm yr−1 We estimate that sod harvesting in the United States results in the net, permanent loss of 12.0 to 18.7 Tg of agriculturally productive soil from sod farms—and associated ecosystem services—every year. The soil losses reported here have important implications in terms of land use planning, transactions involving the purchase of development rights, and tax deductions for

Potential propagule sources for reestablishing vegetation on the floodplain of the Kissimmee River, Florida, USA

After channellization of the Kissimmee River, the primary land use of the drained floodplain was cattle pasture but included sod farms. A project to restore the river began in 1999. One of its goals is to reestablish the three dominant, pre-channelization vegetation types (wetland shrub, broadleaf marsh, and wet prairie) in areas where they previously were found. We investigated whether indicator species of these three vegetation types were present in 53 permanent quadrats on the drained floodplain. All seven indicator species were found in the permanent quadrats. We also examined three potential sources of propagules (relict wetlands, seed banks, and several surrogates of hydrochory) for these indicator species. All seven species were found in adjacent relict wetlands; and six were found in the seed banks of permanent quadrats. Based on binomial logistic regressions, the presence of relict wetlands and surrogates for flooding (relative elevation, total days flooded) can predict the presence or absence of most of these indicator species. Sod farming reduced the presence of wet-prairie and broadleaf marsh indicator species in permanent quadrats, in adjacent relict wetlands and in the seed bank. The potential importance of relict wetlands for the re-vegetation of the floodplain was our most important finding.

ZOYSIAGRASS (ZOYSIA SPP.) RESISTANCE TO FALL ARMYWORM (SPODOPTERA FRUGIPERDA): POLYPHENOLS AND FLAVONOIDS ¿ COMPONENTS OF RESISTANCE

ZOYSIAGRASS (ZOYSIA SPP.) RESISTANCE TO FALL ARMYWORM (SPODOPTERA FRUGIPERDA): POLYPHENOLS AND FLAVONOIDS ¿ COMPONENTS OF RESISTANCE

A Plant Virus as a Bioherbicide for Tropical Soda Apple, <I>Solanum Viarum</I>

© 2007. Research Information Ltd. All rights reserved DOI: 10.1564/18aug07 Tropical soda apple (Solanum viarum, Figure 1; abbreviated: TSA) is an exotic, thorny, perennial shrub that has become a highly invasive weed in the southern USA. TSA is native to Brazil, but has spread to several countries of South and Central America, the Caribbean, Africa, and the Indian subcontinent. In Florida, improved pastures, cattle feedlots, citrus groves, ditches, sod farms, and natural areas are seriously affected by this weed (Ferrell & Mullahey 2007, Mullahey et al. 1993). TSA has been reported to occur also in Alabama, Georgia, Mississippi, Louisiana, Texas, North Carolina, South Carolina, Tennessee, and Pennsylvania (NAPIS, 2003). While some of these infestations have been eradicated, the threat of continued influx has not diminished because cattle, deer, wild hogs, birds, and contaminated hay help to disseminate the seed. TSA has the potential to spread throughout the continental USA (Patterson 1996). The realization of the threat posed by TSA has led to its designation as a “noxious weed” under the Federal and Florida noxious weed statutes. In efforts to stop the weed at its source, namely, the infestations in Florida, all potentially effective methods of control, including biological control, are being examined (DOACS-Florida 2007). TSA infestations in pastures cause the cattle stocking rates to be lowered due to the reduced access and available area for grazing. The livestock production costs go up, and out-of-state cattle shipments face a regulatory dilemma since the cattle are partly implicated in spreading the weed to their destinations. Although TSA foliage is inedible due to the presence of sharp thorns on all parts of the shoot, livestock, feral hogs, deer, raccoons, and birds eat the fruits and disperse the seeds (Coile 1993). Contaminated equipment, hay, grass seed, composted manure, and sod from TSA-infested areas also disperse the seeds. TSA seed is highly viable even after passage through animals’ digestive tracts and is the principal means of initial establishment as well as secondary increases in TSA populations. Mature plants can also sucker and re-establish following mowing and chemical treatment. Besides its weediness, TSA is a potential reservoir of several cropdamaging insects and pathogens (McGovern et al. 1994). A PLANT VIRUS AS A BIOHERBICIDE FOR TROPICAL SODA APPLE, SOLANUM VIARUM

Sales, Value Added and Employment Impacts of the United States Sod Production Industry

Abstract A study using government secondary data in conjunction with primary data collected through a national survey was conducted to assess the importance of the sod production industry to the United States economy. Results indicate that the 2,124 sod farms contributed over $1.72B in gross output or sales impacts to the U.S. economy, $1.31B in value added, employed 13,454 people, and paid $28.6M in indirect business taxes. The top five producing states in terms of sales impacts include Florida ($344M), Texas ($183M), Alabama ($118M), Georgia ($116M) and Oklahoma ($84M), accounting for nearly 50% of total sales.

St. Augustinegrass Fertilizer Trials

ABSTRACT Research was conducted to verify the current fertilization recommendations for St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze) lawns. Currently, a range from 100 to 300 kg nitrogen (N) ha− 1 per growing season is suggested, based on factors such as location in the state, desired maintenance level, soil conditions, etc. Research was conducted at the G.C. Horn Turfgrass Field Laboratory in Gainesville, FL from 2000 to 2002, utilizing medium to high management levels and at a sod farm in Bradenton, FL from 2001 and 2002, under low management conditions. Nitrogen (N) and potassium (K) treatments were arranged in a randomized complete block design with three replications in both locations. In Gainesville, best visual quality was generally obtained with medium (MN) or high nitrogen rates (HN). In Bradenton, MN, and HN rates provided best visual quality responses in 2002 and 2003, but higher rates of N were required than in Gainesville to maintain acceptable quality. This higher N requirement could be due to the longer growing season in Bradenton or to poor turfgrass growth resulting from inadequate pest control. In the absence of biotic or abiotic stresses, the highest rates of N were not necessary to maintain an acceptable quality lawn.

MANAGEMENT OF PEST MOLE CRICKETS IN FLORIDA AND PUERTO RICO WITH A NEMATODE AND PARASITIC WASP

Non-indigenous invasive mole crickets, Scapteriscus vicinus Scudder (Orthoptera: Gryllotalpidae) in Florida and S. didactylus (Latreille) (the “changa”) in Puerto Rico, are being managed with an entomopathogenic nematode, Steinernema scapterisci (Nguyen and Smart) (Rhabditida: Steinernematidae), and a parasitic wasp, Larra bicolor L. (Hymenoptera: Sphecidae). Pest mole cricket populations have declined by 95% in north central Florida since these specialist natural enemies were released and established in the 1980s. Commercial production of the nematode was initiated, nearly 70 billion were applied in 34 Florida counties, and their establishment, spread, and impact on mole crickets were monitored. The infected mole crickets dispersed the nematode rapidly, so that within 6 months these parasites were present in most of the insects trapped in experimental pastures. Three years later, mole cricket populations were reduced to acceptable levels and the bahiagrass had recovered. The nematode was released for the first time in Puerto Rico during 2001 and has persisted; the wasp was introduced in the late 1930s. The geographical distribution of the wasp is being expanded in Florida and Puerto Rico by planting plots of Spermacoce verticillata (L.), a wildflower indigenous to Puerto Rico and widely distributed in southern Florida. Pastures, sod farms, golf courses, landscapes, and vegetable farms in Florida and Puerto Rico are benefiting from biological control of invasive mole crickets.

LIBURNIA PSEUDOSEMINIGRA (DELPHACIDAE: HOMOPTERA), A NEW AND UNUSUAL PEST OF ST. AUGUSTINEGRASS

Abstract No publications have reported delphacid planthoppers (Family Delphacidae) to be turf pests in the United States. In March 2005, a large infestation of the delphacid planthopper, Liburnia pseudoseminigra (Muir & Gifford), was found infesting St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, in a commercial sod farm in southern Florida. Thereafter, a survey was conducted in commercial sod farms in southern Florida to determine the extent of the planthopper infestation in different St. Augustinegrass varieties. The planthoppers were found in low numbers in Floratam, Palmetto, and Seville and were moderately abundant in Bitterblue. However, Classic was clearly the variety supporting large numbers of the planthopper. Liburnia pseudoseminigra was described from Florida and apparently is a native species. Virtually nothing was known about its biology prior to its appearance as a pest of St. Augustinegrass in this study.

Effect of leaf nitrogen concentration versus CND nutritional balance on shoot density and foliage colour of an established Kentucky bluegrass (Poa pratensis L.) turf

A 3-yr field study was conducted in a loam and a sand site to determine the effects of N, P, and K application rates on N status, shoot density and foliage colour of Kentucky bluegrass clippings and to derive critical N values. The experiment was arranged in a completely randomized block design with four replicates and three nutrients, N (0 or 50 to 300 kg ha-1 yr-1), P (0 or 21.8 to 87.3 kg P ha-1 yr-1), and K (0 or 41.7 to 250 kg K ha-1 yr-1), equally broadcast six times per growing season. We examined N concentration values, log-transformed N concentration values, and CND values for compositional nutrient simplexes comprising one (VN1), three (VN3), five (VN5), or 11 (VN11) macro- and micro-nutrients. Critical values for N expressions were obtained from linear relationships with targeted visual shoot density and foliage colour ratings that were closely related to each other (R2 = 0.92). The highest coefficients of determination (0.975 to 0.980) were obtained with VN5 and VN11. The VN5 values were consistent with literature data and across experimental sites, and were the most successful (99% success) in diagnosing N sufficiency in 328 qualified specimens from commercial sod farms. Compared with raw concentrations, the CND transformation reduced from 0.6 to 0.1 the degree of inter-correlation among nutrients in principal component analysis and was amenable to a χ2 distribution of CND indices. Using a critical imbalance index (CNDr2) of 5.6as χ2 value, and a critical CND IN2 index of 1.5 for a 5-nutrient simplex, we diagnosed as imbalanced 179 qualified specimens of which 110 specimens presented excessively high N level among the 328 qualified specimens in commercial stands. The proposed five-nutrient CND norms proved to be effective in diagnosing N status in Kentucky bluegrass clippings across experimental, literature, and survey data sets. Key words: Plant tissue nutrient diagnosis, DRIS, CND, Kentucky bluegrass nitrogen fertilization, turfgrass shoot density, turfgrass foliage colour

Economic Impacts of the Turfgrass and Lawncare Industry in the United States

The turfgrass and lawncare industry in the United States continues to grow rapidly due to strong demand for residential and commercial property development, rising affluence, and the environmental and aesthetic benefits of turfgrass in the urban landscape. Economic sectors of the industry include sod farms, lawncare services, lawn and garden retail stores, and lawn equipment manufacturing. Golf courses were also included in this study as a major industry that depends upon highly managed turfgrass for golf play. Numerous studies have been conducted on the economic impacts of the turfgrass and lawncare industry for individual states or regions; however, this research is the first to report results for the entire United States. This is EDIS document FE632, a publication of the Food and Resource Economics Department, UF/IFAS Extension. Published April 2006. FE632/FE632: Economic Impacts of the Turfgrass and Lawncare Industry in the United States (ufl.edu)

Quantitative and qualitative responses of an established Kentucky bluegrass (Poa pratensis L.) turf to N, P, and K additions

Kentucky bluegrass is a common turf species used on golf courses, sports fields, municipal parks, sod farms, road banks, as well as residential and school yards. Our objective was to determine the effects of N, P, K rates on turfgrass quantitative response (clipping yield and underground turf biomass) and qualitative response (shoot density and foliage colour) under a continuous clipping removal. A 3-yr field study was conducted on two sites, a sand that met the specifications of the United States Golf Association (USGA) and a loam. The factorial experiment was arranged in a randomized complete block design with four replicates and different levels of three nutrients, N (0 or 50 to 300 kg ha-1 yr-1), P (0 or 21.8 to 87.3 kg P ha-1 yr-1), and K (0 or 41.7 to 250 kg K ha-1 yr-1). The maximum clipping yield was produced at the rate of 200 kg N ha-1 yr-1 in the loam and 300 kg N ha-1 yr-1 in the sand. Increasing N rates linearly reduced underground turf biomass. Added P and K had no effect on clipping yield and underground turf biomass. Nitrogen significantly improved shoot density and foliage colour. However, equivalent shoot density and colour ratings required 40 to 80 kg more N ha-1 yr-1 in the sand compared to the loam. Phosphorus and K had no significant effect on shoot density and colour in the loam. Colour response to P and K depended on N rates in the sand. Fertilizer units needed to increase soil test P averaged 6 kg added P ha-1 mg-1 PM-III kg-1 across soil types. To replenish soil K, 7 kg K ha-1 per mg KM-III kg-1 were required in the sand, and 3 kg K ha-1 per mg KM-III kg-1 in the loam. Phosphorus and K fertilizer programmes should account for P and K removals to maintain low to medium fertility levels for P, and medium for K when conditions are similar to those in this research. Key words: Turfgrass clipping yield, underground turf biomass, turfgrass shoot density, turfgrass foliage colour, Kentucky bluegrass fertilization

Seasonal Distribution of Fall Armyworm (Lepidoptera: Noctuidae) Host Strains in Agricultural and Turf Grass Habitats

Male fall armyworm moths [Spodoptera frugiperda (J. E. Smith)] were captured in pheromone traps over a 16- to 24-mo period in selected sites in southern Florida. Molecular markers were used to determine whether individuals were of one of two host strains (historically designated “rice-strain” and “corn-strain”). Traps placed in agricultural areas showed a population peak in the spring (March–May) and fall (October–December), with a prolonged decline in numbers in summer (July–October) and a smaller reduction in mid-winter (January). The host strain distribution during these periods varied significantly, suggesting strain-specific and seasonal population patterns. Both strains were captured in substantial numbers during the spring peak, but surprisingly, only the rice-strain showed an increase in capture rates during the fall, despite the presence of sweet corn throughout this period. Trap captures in a sod (turfgrass) farm were composed almost entirely of the rice-strain and showed a bimodal seasonal distribution similar to that seen in the agricultural areas, with peaks in the spring and fall. These results represent the first indication that the two host strains might have substantially different population dynamics in the overwintering agricultural areas of Florida and suggest that the rice-strain is the predominant fall armyworm pest during the fall and winter growing periods. It further indicates that the two strains can display a markedly different response to seasonal environmental cues. The implications of these findings on our understanding of fall armyworm migration are discussed.

Integrated, long term, sustainable, cost effective biosolids management at a large Canadian wastewater treatment facility

The Greater Moncton Sewerage Commission's 115,000 m3/d advanced, chemically assisted primary wastewater treatment facility located in New Brunswick, Canada, has developed an integrated, long term, sustainable, cost effective programme for the management and beneficial utilization of biosolids from lime stabilized raw sludge. The paper overviews biosolids production, lime stabilization, conveyance, and odour control followed by an indepth discussion of the wastewater sludge as a resource programme, namely: composting, mine site reclamation, landfill cover, land application for agricultural use, tree farming, sod farm base as a soil enrichment, topsoil manufacturing. The paper also addresses the issues of metals, pathogens, organic compounds, the quality control program along with the regulatory requirements. Biosolids capital and operating costs are presented. Research results on removal of metals from primary sludge using a unique biological process known as BIOSOL as developed by the University of Toronto, Canada to remove metals and destroy pathogens are presented. The paper also discusses an ongoing cooperative research project with the Université de Moncton where various mixtures of plant biosolids are composted with low quality soil. Integration, approach to sustainability and "cumulative effects" as part of the overall biosolids management strategy are also discussed.

COMPANY SUES EPA OVER PESTICIDE

EPA IS CONSIDERING THE registration of generic versions of racemic metolachlor, a popular herbicide developed by Syngenta. Its patent expired in 1993. In 1999, Syngenta developed a new version, S-metolachlor, under EPAs Reduced Risk Pesticide Initiative and replaced the old version of the chemical. Now, several generic agrochemical companies are seeking to revive the original material. In either form, metolachlor is a herbicide used to control yellow nutsedge and crabgrass, among other landscape weeds. It is used on golf courses, sod farms, and football and baseball fields. Syngenta is suing to prevent EPA from allowing the registration of the original, racemic version. The granting of this conditional registration would be a clear statement to the public and to the agrochemical industry that EPA no longer values the environmental benefits associated with reduced risk products, says Vince Alventosa, counsel for Syngenta. Dave Deegan, spokesman for the agency, says a decision on generic registration is p...

Soil nitrate monitoring for turfgrass sod farms and other turf areas.

Studies with established turf and golf courses have indicated minimal risk of nitrate pollution of groundwater resulting from turfgrass management, but soil nitrate flux in turfgrass sod production farms and golf courses has received less attention. Information about nitrate-N flux at a particular location can be helpful to the sod producer or the golf course manager when efficiently applying N fertilizers and minimizing risk of nitrate pollution. We used an ion exchange resin capsule system to continuously monitor soil nitrate-N fluxes at 12 sites in southern Rhode Island, including turfgrass sod production farms and a low-maintenance environment. Four capsules were placed in the soil at each site and retrieved at intervals coinciding with management and meteorological events to determine nitrate ion accumulation. We found that the golf course green exhibited significantly higher nitrate-N fluxes than the sod farms and the low-maintenance turf. There was significant interaction between sampling date and study site, indicating that seasonal variation in soil nitrate-N fluxes was affected by turfgrass management. The cultural practice of late fall fertilization to stimulate early spring growth in the following year appeared to present some risk of nitrate loss during the winter from the golf course greens in our region. We conclude that site-specific and time-relevant monitoring is needed to produce and manage turfgrasses in an environmentally sound manner.

Advection and the surface energy balance across an irrigated urban park

The surface energy balance in an irrigated urban park in suburban Sacramento, CA is observed. Three sites extend from the edge of the park to its centre, along a transect which is aligned with the prevailing wind. Direct measurements of the fluxes of net radiation, soil heat flux and evaporation are made at each site and the convective sensible heat is found by residual. Strong advective effects on evaporation are observed, especially in the afternoon and evening. The driving forces for this are the differences in surface and air temperature, and humidity, between the cool, wet park and its warmer, drier built-up surroundings. The control of the surroundings on park evaporation is demonstrated by comparing values with those from synchronous observations in the surrounding suburbs and at an irrigated sod farm just outside the city. Greatest evaporative enhancement is observed at the upwind edge. Throughout the afternoon evaporation considerably exceeds the net radiation. This is interpreted to be due to the microscale leading-edge effect which appears to be restricted to a fetch of about 20 m. Further into the park evaporation also exceeds the net radiation in the afternoon due to the oasis effect. At all sites the sensible heat flux density in the afternoon is negative. Daily and daytime total evaporation from the park is more than 300% that from the integrated suburban area, and more than 130% that from the irrigated rural grass site. The unlimited water supply and the high temperatures of the park allow it to behave like a wet leaf in that its surface temperature seems to be ‘thermostatically’ controlled—it never rises more than a few degrees above that of the park air and for much of the day is cooler than the park air. Copyright © 2000 Royal Meteorological Society

Advection and the surface energy balance across an irrigated urban park

The surface energy balance in an irrigated urban park in suburban Sacramento, CA is observed. Three sites extend from the edge of the park to its centre, along a transect which is aligned with the prevailing wind. Direct measurements of the fluxes of net radiation, soil heat flux and evaporation are made at each site and the convective sensible heat is found by residual. Strong advective effects on evaporation are observed, especially in the afternoon and evening. The driving forces for this are the differences in surface and air temperature, and humidity, between the cool, wet park and its warmer, drier built-up surroundings. The control of the surroundings on park evaporation is demonstrated by comparing values with those from synchronous observations in the surrounding suburbs and at an irrigated sod farm just outside the city. Greatest evaporative enhancement is observed at the upwind edge. Throughout the afternoon evaporation considerably exceeds the net radiation. This is interpreted to be due to the microscale leading-edge effect which appears to be restricted to a fetch of about 20 m. Further into the park evaporation also exceeds the net radiation in the afternoon due to the oasis effect. At all sites the sensible heat flux density in the afternoon is negative. Daily and daytime total evaporation from the park is more than 300% that from the integrated suburban area, and more than 130% that from the irrigated rural grass site. The unlimited water supply and the high temperatures of the park allow it to behave like a wet leaf in that its surface temperature seems to be ‘thermostatically’ controlled—it never rises more than a few degrees above that of the park air and for much of the day is cooler than the park air. Copyright © 2000 Royal Meteorological Society

Composting of pulp and paper mill fly ash with wastewater treatment sludge

Wastewater treatment sludge and power boiler fly ash were combined and composted in mixed and static windrows 50 m long, 4 m high and 6 m wide. Moisture content was maintained above 50%. The final compost had a pH of 8.5, contained high concentrations of specific nutrients, and an average C:N ratio of 43:1. All metal, PCB, chlorophenol and PAH concentrations were below levels stipulated by local regulations. Over the first 8 weeks of the composting period dioxin concentration decreased by 45% to 41 pg/g TEQ. Leachate tests indicated minimal (<0.1 mg/l Cu and Pb; <50 mg/l Na, P, and SO 4 −2) leaching of contaminants from the composted material. Application of compost (8 cubic yards/acre) at a sod farm improved soil characteristics as measured by a number of parameters. The dioxin concentration in the final soil/compost mixture was 3 pg/g TEQ, allowing the soil/compost mixture to be classified as agricultural soil. It was concluded that composting produced an acceptable soil conditioner attractive for large volume users of inexpensive soil material (sod farms, golf courses, land reclamation sites).