E) La relación de causalidad
III. RESPONSABILIDAD CIVIL POR TRANSMISIÓN DE ENFERMEDADES O
1. La vertiente penal de la transmisión por los progenitores de enfermedades o defectos
Turfgrasses often are valuable components of the environments where people live, work, and play. They can be used to provide an essential base for sports and leisure activities in such settings as baseball fields, football and soccer fields, golf courses, and school grounds. They also
prove useful in soothing landscapes in such places as office parks, cemeteries, and home gardens. Yet turf also is seen by some as problematic, for it sometimes contributes to a net loss of oxygen in the atmosphere and often requires considerable water, the conservation of which is a main reason for switching to recycled water in the first place. Also, turfgrass may require the application of fertilizer or other chemical treatments, which may in some instances, foster the contamination of soil or other nonpoint source pollution problems. The key to avoiding all these potential problems is to use turf only where necessary and to choose a variety of turf that best fits the intended application.
Selecting a turfgrass involves considering a number of factors, including the intended use of the turf, the desired appearance, and the degree of required maintenance. The choice of a turfgrass is also dictated by geography, the soil and biotic conditions under which grass will be grown, and the climate, particularly temperature, rainfall, and the amount of sunlight. Table VI9 lists all species commonly grown in California, divided into warm and coolseason species. Warm season grasses grow predominantly in southern California, in the Central Valley, and along the Pacific coast as far north as San Francisco. Coolseason grasses are grown throughout California, except in the state’s deserts and southernmost regions.
Warmseason turfgrasses usually lose their greenness and go dormant in winter if the average temperature drops below 50 to 60 ˚F. Some may die if exposed to subfreezing temperatures for extended periods. Coolseason turfgrasses do not ordinarily lose their greenness unless the average air temperature drops below 32 ˚F for an extended period. They regain their greenness as soon as temperatures rise above freezing and are not usually damaged by subfreezing temperatures. It should be noted that grasses vary in the hue and intensity of their color, from the bright green of Kentucky bluegrass (Poa pratensis) to the grayish green of common bermudagrass (Cynodon spp.).
The following information applies to the turfgrasses listed in Table VI9 when such grasses are grown in California:
Bentgrasses (Agrostis spp.)
Though they tolerate close mowing and can provide lawns of good quality, bentgrasses require more maintenance than other lawn grasses and extra effort to ward off disease during the summer.
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The colonial variety of bentgrass (Agrostis tenuis) may spread very slowly by short rhizomes and, less often, short stolons. Its layer of thatch extends above and below the soil.This variety is adapted to the northern coastal climate and does not form a dense turf in other areas.
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The highland variety (Agrostis spp. cv. “Highland”) is adapted to valley climates and will survive extensive droughts. It forms solid patches of grass that turn a frosty blue from morning dew during cool seasons. It may form both short rhizomes and stolons.·
The creeping variety (Agrostis palustris) is used for specialized turf, such as golf, bowling and tennis greens. The skill and expense required to maintain it usually preclude its use for home lawns. This variety spreads by stolons to form a mat or layer of thatch above the soil.Bluegrasses (Poa spp.)
Three distinct bluegrasses are grown in California.
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The annual variety of bluegrass (Poa annua), considered a weed, is well adapted to the cool, moist conditions of California’s Pacific coast from Los Angeles to the Oregon border. It is the predominant species on golf greens, bowling greens, and croquet courts. It also quickly invades the dead and worn areas of a significant number of overused sports fields and parks, as it is very well suited to the coastal climate and is a prolific producer of seeds. This variety often successfully invades golf and bowling greens because it tolerates very close mowing. Shallowrooted and drought intolerant, this turfgrass is a shortlived perennial in cool, moist climates and persists as an annual in sites with hot, dry summers.·
Kentucky bluegrass (P. pratensis) is the standard of quality among turfgrasses in areas where it is well adapted. In areas of marginal adaptation, it suffers from diseases, invasion by weeds, and stress related to high temperatures. Each variety of Kentucky bluegrass has characteristic virtues and faults, with none adapted to hot valley climates. Blending equal portions of several seed varieties usually leads to optimal results. For example, a seed mixture of Kentucky bluegrass and perennial ryegrass is more resistant to disease than is bluegrass alone.·
Roughstalk bluegrass (P. trivialis) is a shortlived perennial that is well adapted to moist, shady sites. Due to its superior performance during winter and after close mowing, it is commonly used to overseed dormant bermudagrass on golf putting greens.Fescue (Festuca spp.)
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Hard and red fescues (Festuca longifolia and F. rubra) are recognizable by their fine texture and, thus, are also known as “fineleaf” fescues. They do not prosper in hot climates, except in shady, dry situations, and they do not tolerate being closely mowed or excessively fertilized. Their color, texture, and pattern of growth make them excellent companion grasses for Kentucky bluegrass, as long as these moderately droughttolerant grasses are grown in moderately shady exposures or dry soil. Fine fescues seldom exceed 8 in. (20 cm) in height, except when in flower, and thus can be useful where a lowmaintenance lawn is desired, such as at a summer cabin at cool mountain elevations where a single mowing will remove the seed heads. They can also be used for controlling hillside erosion in urban areas, such as unmowed ground covers along roadsides, and for golf course roughs, parks, and cemeteries.·
Tall fescue (F. arundinacea), when densely sown, produces a moderately coarsetexturedlawn that is trouble free and uniform in appearance. In a mix with other coolseason grasses, individual tall fescue plants appear as coarse weeds. New selections, known as turftype and dwarftype tall fescues, are finer textured and shorter than older selections. Bare or worn spots within tall fescue stands must be reseeded, as these grasses do not produce runners. Tall fescues are quite tolerant of drought and heat and require the least maintenance of all coolseason grasses in California.
Ryegrass (Lolium spp.)
Two distinct ryegrass species are commonly planted in California.
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Annual ryegrass (Lolium multiflorum), quite coarse textured, is used only to overseed dormant bermudagrass or to provide a temporary annual cover.·
Perennial ryegrass (L. perenne), a strong performer in coastal fog belts and adequate elsewhere, is often used in seed mixtures with Kentucky bluegrass. It germinates quickly and provides a rapid turf cover and so is also used to overseed winterdormant Bermuda grass lawns. It has no rhizomes or stolons, so bare or worn areas should be reseeded. Weeping alkaligrass (Puccinellia distans) This grass is only marginally adapted to the cool central and northern coast, as well as to mountain regions. Its only use is in areas with severe soil or water salinity problems since it does not produce an attractive, durable lawn. Because weeping alkaligrass tolerates low mowing, it may provide an acceptable alternative for winter overseeding of bermudagrass on saltaffected golf greens.Bermudagrass (Cynodon dactylon)
This grass is well adapted to the warm regions of California. Spreading both by rhizomes and stolons, it can be a troublesome invader of other areas in a landscape. Short mowing helps produce a neat, restrained turf. Bermudagrass does not tolerate shade and turns brown with continued low temperatures. Hybrid bermudagrasses are propagated vegetatively and require a high level of management. If ordinary management is available, common bermudagrass is preferable. Bermudagrasses are highly drought and salt tolerant.
Seashore paspalum (Paspalum vaginatum)
This grass grows well near the ocean, where it is subjected to saltwater. It has excellent tolerance of salinity.
St. Augustine grass (Stenotaphrum secundatum)
This grass is a coarsetextured, subtropical grass with excellent tolerance of shade, drought, and salinity.
Kikuyugrass (Pennisetum clandestinum)
This grass is a weedy grass grown in coastal and some inland areas of California. This native of highaltitude equatorial Africa thrives in climates with moderate, even temperatures. Sometimes mistaken for St. Augustine grass, kikuyugrass forms vigorous stolons and has slightly flattened, hairy leaf sheaths and blades with files of hairs. It tolerates low fertility, drought, and frequent close mowing.