Blue Mountains National Resources Institute

Wanted: DEAD!

Whitetop

Alias: Hoary cress, pepperwort

Stems: Up to 3 feet high.

• Leaves: Grayish-green, up to 4 inches long, shaped like arrowheads. Nearly entire to finely toothed and bearing soft fine hairs. Lower leaves stalked, upper reduced and sessile.
• Flowers: Numerous and small, four sepals and petals, petals about 1/4-inch long and white. Flowering period is in early May.
• Fruits: Inflated, 1/8-inch long, heart-shaped at base and topped by a persistent style. Prominently veined at maturity, bearing two (or four) reddish-brown, small, flat seeds.

Whitetop can establish itself in a variety of soil types and environmental conditions: dry pastures, hay meadows and roadsides, cultivated crops. A single plant can send out 400 shoots in a year. Roots develop to depth of several feet, making control difficult. It spreads by seed and root.

Control: Integrated pest management is the best method of controlling this weed.

• Biological: Dense stands of perennial grasses will out-compete whitetop. Pasture grasses will slow spread if not overgrazed. Growing small grains in infested fields will suppress whitetop once a canopy is formed. No insects or parasites are available in the United States (as of Nov. 1991).
• Chemical: Most easily controlled with foliar herbicides applied during rosette stage. Depends on where infestation is located, what kind of herbicide and application is allowed.
• Mechanical: Cultivating fallow ground no more than 10 days after weed emergence will eventually eliminate the weed. Close mowing will also reduce seed production but will not eliminate.

Report all sightings to your local Weed Board