Diseases of Orchardgrass - PowerPoint PPT Presentation

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Diseases of Orchardgrass

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  1. Diseases of Orchardgrass Jon Repair Extension Agent, Crop and Soil Sciences (540) 463-4734 jrepair@vt.edu

  2. Disease Control Strategies • Sow only disease-free seed of improved, well-adapted cultivars • Late harvest immediately after or close to first killing frost of Orchardgrass, leaving 3 to 31/2 inches of growth. (Additional regrowth should then be minimal) • Careful, controlled burning?? (how about grazing) of dead grass in early spring if pastures or hayfields are severely affected

  3. Disease Control Strategies • Rotate at least two years with non-grass crops where practical (Annual or perennial legume or perhaps a brassica) • Suppress weed grasses by cultural (additional harvesting) or chemical means (hard to accomplish)

  4. Practices to Avoid • Excessive rates of fertilizers high in quickly available nitrogen (Use split applications) Except with late fall application (Oct.15 thru Dec.1) • Pure, dense stands of a single cultivar Mix with either similar cool season grasses or legumes

  5. Practices to Avoid • Leaving a heavy mat of hay on grass during wet weather • Close grazing and/or mowing (2.5 to 3 inches) when appropriate. Be sure to leave some leaf area remaining for less stressful quicker re-growth.

  6. Anthracnose summer depression Colletotrichum graminicola Lesions first observed as water- soaked spots Lesions expand to reddish brown to orange Associated with warm, wet conditions

  7. Brown Stripe Scolecetrichum graminis (Cercosporidium graminis) Overwinters as masses of mycelia in living leaves and crop debris Produce spores in spring Rain splashed and wind-blown rain Ceases during hot, dry summer Resumes in wet fall conditions

  8. Stagonospora Leaf Blotch Stagonospora arenaria Overwinter as pycnidia in dead leaf tissue Infection takes place during cool, wet, spring weather Small, slightly elongate-to-ellipitcal lesions form on leaves, leaf sheath early in growing season Pynidia (fruiting bodies), golden-brown to black form in the dead tissue of lesions

  9. Powdery Mildew Blumeria graminis f.sp. dactylidis Lesion are at first small and white effuse patches Pathogen is entirely superficial except for haustoria which penetrate the epidermal cells Disease is favored by cool, damp weather and high rates of nitrogen Can affect value for commercially sold hay

  10. Summer Blight Drechslera dactylidis Associated with rainy conditions Lesions first appear irregular and spindle shaped, faint brick color to gray surrounded by chlorotic tissue Under severe conditions lesions fuse to blight entire leaf Wind-blown conidia Pathogen survives in colonized dead tissue

  11. Barley Yellow Dwarf Virus BYDV, luteovirus Aphid transmitted Infection adds stress to orchardgrass Cummulative effect over life of stand

  12. Keys to Reducing Impact of Orchardgrass Diseases • Maintain proper fertility • Well adapted Orchardgrass cultivars • Rotate with non-grass host for two years before establishing (Perennial or annual legume) • Follow recommended mowing and grazing practices • Mixtures of grasses or cultivars • Suppress weed species in stand

  13. Questions?