Oklahoma State University

Pest Management

Pest Management

Few pests of economic importance have been recorded on switchgrass. However, this does not imply the crop will always be free from attack. As the acreage of switchgrass monocultures increases, a corresponding increase in pests is likely.


Many fungal diseases have been reported for switchgrass including rusts, smuts, leaf spots, and crown and root rots. Most of these diseases however, have not been documented to be of economic importance. Like traditional crops, some fungal diseases will have the potential to affect biomass and seed production in the future. Rust (Puccinia emaculata) has been reported from numerous states, including Oklahoma. Rust spores are airborne and land on switchgrass plants. Under the right environmental conditions, the spores germinate and infect the plant. At first, light yellow flecks on the surface of the leaves or on culms can be observed. As the disease progresses, numerous lesions containing mature small brown spores erupt through the leaf surface. Rusts require an alternate plant host to complete its entire life-cycle, the alternate host(s) are plant species in the spurge family. Control is achieved by planting resistant varieties and possibly the use of foliar applied fungicides.

Another disease which has been documented to reduce switchgrass biomass is head smut caused by Tilletia maclagani. For a study conducted in Iowa, it was determined that head smut caused significant reductions in biomass yields and stand decline. The fungi survive as spores on seed and in infested soils. Spores infect coleoptiles before seedling emergence in the spring. The fungus grows through the plant and primarily colonizes at points of plant growth. In the developing seed head, the fungus displaces the kernel and upon maturity bunt balls emerge releasing spores which are dispersed by wind, rain and healthy seed. Control is facilitated through clean seed, plant resistance, and fungicide seed treatments.

In addition to fungal diseases, switchgrass has been found to be susceptible to some strains of barley yellow dwarf virus as well as Panicum mosaic virus. At this time, the importance of diseases caused by viruses, bacteria, and nematodes is not known, and there maybe biomass yield reductions attributable to these pathogens in the future.


Few insects have been identified as potential pests in switchgrass. Grasshoppers are known to feed on switchgrass, but the extent of their damage has not been quantified; however, it is known to be highly variable from year to year. Commonly found insects on switchgrass include aphids, leafhoppers, blister beetles, chinch bugs, grasshoppers, stem bores, and wireworms. Several beneficial insects also have been reported including ants, rove beetles, ground beetles, parasitoid wasps, and spiders.


Both weedy grasses and broadleaf weeds can be serious problems during switchgrass establishment, but usually only minor problems after the fi rst year. The array of weeds found in any field depends on the previous use of the land and nearby plants whose seeds may have blown or washed onto the site.

In a field near Stillwater with an 11-year old stand of Kanlow switchgrass, rough fl eabane (Erigeron strigosus) was the only weed in the early growing season, and annual bromes were the only cool-season weeds found after biomass harvest. Both were shaded out by switchgrass growth and neither affected production. During the establishment phase of a stand, the presence of weeds may be highly variable.

In a single field near Haskell, Okla. the following weeds were identified during the establishment stage of a switchgrass planting.
Grasses Broadleaf and other weeds
Crabgrass (Digitaria spp.)
Goosegrass (Eleusine indica)
Pigweed (Amaranthus spp.)
Nutsedge (Cyperus esculentus)
Carpetweed (Mollugo verticillata)
In a single field near Stillwater, Okla., the following list of weeds were identified during the establishment stage.
Grasses Broadleaf and other weeds

Bermudagrass (Cynadon dactylon)
Crabgrass (Digitaria spp.)
Foxtail (Setaria spp.)
Goosegrass (Eleusine indica)
Johnsongrass (Sorghum halepense)
Signalgrass (Brachiaria platyphylla)
Stinkgrass (Eragrostis cilianensis)
Ticklegrass (Agrostis spp.)
Witchgrass (Panicum spp.)

Black and silverleaf nightshade (Solanum spp.)
Curly dock (Rumex crispus)
Field bindweed (Convolvulus arvensis)
Goathead or puncture vine (Tribulus terrestris)
Honeyvine milkweed (Ampelamus albidus)
Honey locust (Robinia spp.)
Horsenettle (Solanum carolinense)
Morningglory (Ipomoea spp.)
Nutsedge (Cyperus esculentus)
Passionvine (Passiflora spp.)
Pigweed (Amaranthus spp.)
Virginia creeper (Parthenocissus spp.)


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