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Smuts, Biodiversity

Posted by | February 18, 2009

Banning Smuts

Smuts are fungi that infect grasses, including cereal crops such as wheat and corn. Infected plants are often stunted, though the reduced size is not noticeable until maturity. If not detected before harvest, millions of fungal spores are released, contaminating healthy kernels or landing on the soil to infect the next year’s crop.

For grain and grass seed growers, smuts are a big deal. In 2005, for instance, nearly 15 million pounds of grass seed valued at $9 million were exported from the U.S. to China. China and other countries ban imports of contaminated seed, so keeping smuts in check is economically important for U.S. growers.

But, as associate professor of plant pathology Lori Carris points out, “Identification of smut fungi found in grass seed shipments is difficult, as many closely related species have morphologically similar spores.” This is a critical issue for Kentucky bluegrass growers in the Pacific Northwest, as Chinese quarantine officials have said that 20 to 30 percent of seed exports from the Pacific Northwest are “highly contaminated.” The problem is, the species of smut Chinese scientists say is infecting the imported seed isn’t known to infect bluegrass. The infection could be a contaminant from some other source–for example, weedy grasses–or perhaps a new species.

Carris and her colleagues have turned to genetic “fingerprinting” tools in order to distinguish one species of smut from another. Correctly identifying the infectious agent is a necessary step in the control of the fungus through seed treatments, weed control, or genetic resistance.

WSU plant pathologist Lori Carris hunting for smut fungi in grasses growing alongside the road.

WSU plant pathologist Lori Carris hunting for smut fungi in grasses growing alongside the road. Bottom: Wheat heavily contaminated with smut from cheatgrass. Cheatgrass seed and pieces of bunted (smut-infected) cheatgrass seed are visible among the grains of wheat.

For more information on plant pathology at WSU, please visit: http://plantpath.wsu.edu/.


Diverse Roles Make for Rich Diversity

Find a niche and fill it: that’s the key to biodiversity, according to a recent study by WSU entomologist William Snyder. He and his team studied parasitic wasps and their aphid prey. More than the sheer number of species in an ecosystem, biological diversity, it turns out, is a matter of non-overlapping roles.

“Diversity is beneficial because at some point as you’re adding more species, you’re adding species that do different things,” Snyder said.

Snyder’s study provides support for sustainable agriculture practices and offers guidance on how best to maintain biological control of agricultural pests. Understanding how to control aphids is important as aphids are a common vector of many viruses that infect plants.

Snyder’s team found that increasing the number of wasp species on a test plot increased the consumption of aphids only if each wasp species targeted a different kind of aphid. Their findings show that for efficient biological control of pests, the best recipe is to use multiple agents (e.g., wasps) that don’t have overlapping prey preferences. He said the study also suggests why sustainable agricultural systems have relatively few pest problems despite their minimal use of pesticides.

Snyder’s team is developing tools to predict which biocontrol agents will work best together. This information can be used to design communities of agents best suited to controlling particular pests.

Parasitic wasps prey on aphids

Some parasitic wasps prey on aphids and act as a natural biocontrol. Understanding how to control aphids is important as aphids are a common vector of many viruses that infect plants.