Transcript Diseases
The Environment of Turfgrass Pathogens HOST PLANT DISEASE PATHOGEN ENVIRONMENT Pathogen Life History dispersal infection 2O cycles survival colonization reproduction Pathogen Life History environment dispersal infection host host host 2O cycles environment colonization environment host environment survival reproduction host GRASS GRASS PATHOGENS ENVIRONMENT LOW DISEASE POTENTIAL HIGH DISEASE POTENTIAL GRASS GRASS PATHOGENS ENVIRONMENT LOW DISEASE POTENTIAL SEASON WEATHER LANDSCAPE HIGH DISEASE POTENTIAL LANDSCAPE EFFECTS Highly exposed LANDSCAPE EFFECTS Low air movement Shading In natural ecosystems, disease is common, but epidemics are rare Disease on individual plant Disease across a population = epidemic Turfgrass is prone to epidemics •Monoculture •High plant density Leaf to leaf hyphal growth CANOPY Two parts of the environment ROOT ZONE Above-ground environment for pathogens Positive factors Nutrients Sugars and amino acids from plant (wounds), air (pollen), insects (honeydew) Above-ground environment for pathogens Positive factors Moisture Atmospheric (humidity) Supports fungal growth (>95%RH) Prevents dessication Free moisture (leaf wetness) Needed for spore germination Bacterial growth and mobility Nutrient transport Sources: dew, guttation, rain Dew Guttation Above-ground environment for pathogens Negative factors Ultraviolet light • Lethal and mutagenic Air movement (wind) • Causes drying of leaf surface • Some beneficial effects for pathogen, however: - Evaporative cooling - Pathogen dispersal Effects of some cultural practices on canopy environment Mowing provides wounds Source of nutrients Point of pathogen penetration Irrigation Lengthens leaf wetness period Increases canopy humidity Cools leaf surface By design, turf grass is planted in high densities. This results in: - Reduced ultraviolet penetration - Reduced leaf temperatures - Reduced air movement through canopy - Increased canopy humidity - Increased leaf wetness period Below-ground environment for pathogens • Pathogens typically located within top 8 inches of soil profile • Most are stationary • Nutrients and host plant must come to pathogen • Pathogens remain dormant unless provided with nutrients 3 CANOPY THATCH ROOT ZONE Two parts of the environment 3 CANOPY Two parts of the environment Little to no UV Leaf wetness nearly continuous THATCH ROOT ZONE Very high humidity 3 CANOPY Two parts of the environment “psuedoroot zone” THATCH ROOT ZONE Growth and infection by root pathogens! Summary • Disease epidemics are uncommon in natural stands of grass • Cultural practices cause turf grass to be prone to epidemics • Cultural practices modify the environment to be more consistently favorable to pathogen growth and infection