Integrated Disease Management Disease Resistance and Cultural Controls

Fungicides Disease Resistance Environmental Manipulation Disease Management Host Nutrition Disease Management Triangle Now that weve covered fungicides lets turn to the Host side of the Disease Management Triangle and discuss Disease Resistance and Host Nutrition

1. What is disease resistance? 2. Why is it important to consider disease resistance when selecting a turfgrass species and/or cultivar for a particular use and site? 3.What impact do major and minor nutrients have on turf disease? 4.What are some examples of disease suppression through environmental manipulation? 5.Be prepared to draw disease triangles and disease management triangles for each of the diseases covered in the following sections. Knowledge Requirements When you complete this section, you should be able to answer these questions

DISEASE RESISTANCE Disease resistance is a genetically controlled, physiological response of a host plant to a pathogen that limits disease severity or incidence.

DISEASE RESISTANCE 1.Some species of turfgrass are more resistant to particular diseases than other species. Examples: Anthracnose is severe only on bentgrass and annual bluegrass. Spring dead spot is severe only on bermudagrass. Gray leaf spot is common on St. Augustinegrass, tall fescue, and perennial rye, but not on other grasses.

DISEASE RESISTANCE 2. Some cultivars within a species are more resistant to particular diseases than other cultivars. Examples: Tall fescue cultivars that differ in susceptibility to leaf blotch Bluegrass cultivars that differ in susceptibility to leaf rust Differences in pink patch among ryegrass cultivars Susceptible Resistant

Fungicides Host Resistance Environmental Manipulation Disease Management Host Nutrition Disease Management Triangle

Disease Management through Manipulation of Host Nutrition 1.Most info. on the effects of host nutrition on disease deals with nitrogen. NITROGEN

Disease Management through Manipulation of Host Nutrition 1.Most info. on effects of host nutrition on disease deals with nitrogen. 2. Nitrogen enhances certain diseases (e.g. Pythium blight, spring dead spot, brown patch) and it suppresses other diseases (e.g. dollar spot, anthracnose). NITROGEN

Disease Management through Manipulation of Host Nutrition Enhancement of Disease by Nitrogen 1. Nitrogen enhances some foliar diseases (eg. Pythium blight, brown patch) by promoting the rapid production of young leaf tissue that is less resistant to fungal enzymes and toxins than older tissue.

Disease Management through Manipulation of Host Nutrition Enhancement of Disease by Nitrogen 1. Nitrogen enhances some foliar diseases (eg. gray leaf spot, Fusarium patch) by promoting the rapid production of young leaf tissue that is less resistant to fungal enzymes and toxins than older tissue. 2. Nitrogen enhances root diseases by inhibiting root production in cool-season grasses, or by stressing roots through the production of excessive foliage in cool- and warm-season grasses.

Disease Management through Manipulation of Host Nutrition Suppression of Disease by Nitrogen Nitrogen can suppress certain diseases (eg. dollar spot, anthracnose) by inhibiting leaf senescence (aging).

Leaf senescence is common in older leaves of turfgass plants. These senescing leaves are more susceptible to certain pathogens than non-senescing leaves. Nitrogen applications can delay leaf senescence, thereby reducing certain diseases. Examples: dollar spot and anthracnose. Senescing leaves

Disease Management through Manipulation of Host Nutrition Suppression of Disease by Nitrogen Nitrogen can suppress certain diseases (eg. dollar spot, anthracnose) by inhibiting leaf senescence stimulating leaf growth to the extent that diseased portions of leaves are mowed off (e.g. dollar spot, red thread, leaf rust). or by

Disease Management through Manipulation of Host Nutrition POTASSIUM (K) 1. Some research suggests that K suppresses a few diseases (eg. snow molds) but evidence is not strong.

Disease Management through Manipulation of Host Nutrition POTASSIUM (K) 1. Some research suggests that K suppresses a few diseases (eg. snow molds) but results are not extensive. 2. K is considered an element that will increase turfgrass tolerance to stress (heat, drought, disease, etc.). However, K should only be applied according to soil test results. High applications of K may result in salt injury to turf.

Disease Management through Manipulation of Host Nutrition Phosphorus (P) There is no direct information indicating that P suppresses disease symptoms. However, P may enhance tolerance to root diseases through its positive effects on root growth in young plants.

Disease Management through Manipulation of Host Nutrition Minor Elements There is very little information on the effects of minor elements on turf disease. Some evidence suggests that Mn and Zn are suppressive to Take-All Patch and Take-All Root Rot. (Fe, Mn, Zn, Cu, Mo, B, Cl)

Fungicides Host Resistance Environmental Manipulation Disease Management Host Nutrition Disease Management Triangle A review of the Environmental Manipulation side of the Triangle

Disease Management through Environmental Manipulation Examples 1.Reduction in the duration of leaf wetness will reduce severity of most foliar diseases of turfgrasses. This can be accomplished by: A. Reducing shade – eg. removing or trimming trees and shrubs. B. Increasing air circulation – eg. using fans to dry turf. C. Avoiding irrigation in late afternoon and early evening – This will allow turf leaves to dry before nightfall.

Disease Management through Environmental Manipulation Examples 2. Increasing soil pH with lime or decreasing pH with ammonium sulfate may suppress certain diseases of turfgrasses. For example, the acidifying effect of ammonium sulfate suppresses the growth of the fungi that cause take-all patch of bentgrass and spring dead spot of bermudagrass.

Disease Management through Environmental Manipulation Examples 3. Reducing soil compaction and thatch will limit the severity of virtually every turfgrass disease. Soil compaction and thatch are the cholesterol and fat of turfgrass health

You should now be familiar with the basic components of a Disease Triangle and a Disease Management Triangle. The following images are examples of each.

Gaeumannomyces graminis Creeping bentgrass Take-All Patch Soil temp °F Soil pH >6.2 High soil moisture Example of a Disease Triangle Name of diseaseName of pathogen Name of host(s) Environmental factors required for disease to develop

fenarimol, azoxystrobin Take-All Patch Species other than bentgrass are resistant. Bentgrass cultivars with some resistance include Regent, Procup, Putter. Decrease soil pH with ammonium sulfate; avoid use of lime; improve soil drainage. Increasing N can suppress foliar symptoms. Increasing soil Mn can suppress root symptoms. Example of a Disease Management Triangle Fungicides registered for control Disease Resistance Host Nutrition Environmental Manipulation

End of IDM - Disease Resistance and Cultural Controls