PEST RISK ANALYSIS (PRA) TRAINING Group Exercises Manual

PEST RISK ANALYSIS TRAINING - GROUP EXERCISES MANUAL GROUP EXERCISE NO. 2
Example No. 6 – Woolly Cup Grass 6
SCENARIO: Routine sampling of seed imports by the Canadian Food Inspection Agency, the
NPPO of Canada, has led to the detection of woolly cup grass (Eriochloa villosa) in millet seed
for planting. Woolly cup grass is a regulated weed in seed lots in Canada. A PRA has been
initiated to determine if it should also be regulated under Canada’s Plant Protection Act.
PEST DATASHEET:
Identity: Eriochloa villosa (Thunb.) Kunth (Family: Poaceae, Tribe: Paniceae (millet tribe)).
Common name: Woolly cup grass.
Habitat: In its native range, E. villosa is mainly found in grassy places, roadsides,
wastelands, and rice fields. In North America it is primarily a weed of cultivated fields and
disturbed soils. It thrives in crop rotations that include maize (e.g. maize-maize or maizesoybean
rotations).
Distribution: Origin: Temperate and subtropical Asia (eastern China, Japan, North and
South Korea, parts of Mongolia, the Amur and Primorye regions of eastern Russia, and
Taiwan). Present: The Caucasus region; western Siberia; the Ukraine; France; the United
States (introduced in 13 states but most problematic in the northern, maize growing area (e.g.
Illinois, Iowa, Minnesota, Wisconsin)). Absent: Africa; Australasia; most of Europe; Central
and South America.
Note: E. villosa was reported for the first time in Canada in the summer of 2000, when a
small population was noticed growing in experimental barley plots near Montreal, Quebec.
The population continued to overwinter and spread until 2002, when the provincial
government initiated an eradication program. By 2003 E. villosa had been eradicated from
the site, and surveillance is ongoing to detect and remove plants that emerge from the seed
bank.
Biology and Dispersal: E. villosa is a tall annual grass that uses the C 4 photosynthetic
pathway, suggesting a possible advantage in hot or dry climates. It is a prolific seed producer,
producing up to 164,000 seeds per plant under ideal conditions. Seeds tend to germinate
earlier than those of other annual grass weeds, and often germinate continuously over the
growing season in a series of germination flushes. Plants produce stolons early and branch
extensively later in the season, so that single plants occupy and disperse seed over a large
area. Little information is available on dispersal mechanisms, but it is assumed that seed
generally falls close to the parent plant, or travels short distances on the wind. Animals may
be involved in seed dispersal as well. Humans are an important vector of E. villosa seeds, and
may disperse them as contaminants in crop seed or through the movement of dirty farm
machinery.
Damage: In the United States, E. villosa is an increasingly serious pest in maize and soybean
crops, particularly in the midwest. It reduces crop yields through competition and increases
the cost of weed control. Yield losses in maize have been estimated at up to 50%. In Canada,
maize and soybeans are produced primarily in Ontario and Quebec, with the value of maize
production estimated at $688 million in 1997.
Control: Woolly cup grass is more difficult to control than many other grass weeds. It
requires the integration of cultural and chemical methods, and is tolerant to several of the
herbicides used to control other grass weeds in maize. In the United States, increases in
producers’ operating costs have been estimated at 18% for additional herbicides alone.
6 NOTE: This example was developed specifically for use in the IPPC PRA training course. The
scenario is not real. The data sheet is based on the Canadian PRA for Eriochloa villosa (CFIA 2002).
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