Diseases in Orchardgrass

Major diseases of orchardgrass in our area has no quick fix yet, but fertility management helps.
Diseases in Orchardgrass - Articles
Diseases in Orchardgrass

Fig. 1. Brown stripe on orchardgrass

Last week my orchardgrass fields were beginning to show some brown areas on the leaves but today (Monday) they looked like they were dying. Then when I got back to the office, I had three emails and two phone messages about diseased orchardgrass fields. Below are some pictures and descriptions by Erik L. Stromberg, Extension Plant Pathologist at VPI, of the major orchardgrass leaf diseases in our area of the country. Unfortunately, there is no quick fix yet for this problem. The best management for these foliar diseases is optimum soil fertility and to remove the infected tissue and hope for less conducive disease weather during orchardgrass regowth.

Brown Stripe (see Fig. 1)

  • 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

Leaf blotch (see Fig. 2)

  • Overwinter as pycnidia (fruiting bodies) 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
  • Pycnidia are golden-brown to black form in the dead tissue of lesions

Powdery mildew (see Fig. 3)

  • 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

Summer blight (see Fig. 4)

  • 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 (reproductive spores)
  • Pathogen survives in dead tissue

Barley yellow dwarf virus (see Fig. 5)

  • Transmitted by aphids from plant-to-plant
  • Infection adds stress to orchardgrass
  • Cumulative effect over life of stand

Authors

Forage Crop Establishment, Management and Utilization Perennial Warm-Season Grass Establishment and Management

More by Marvin Hall, Ph.D.