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Whitetop (hoary cress) is currently in the pre-bloom or early bloom stage throughout Delta County. Photos are available at www.cwma.org.
Click on weed info, and click on hoary cress under the B list. The link to CDA Fact Sheets lists complete control information.
Due to the rhizomes of this perennial weed, mechanical control provides minimal control. Diligent digging can provide control of very small infestations. Hand-pulling of above-ground plant parts is ineffective. Successful digging requires complete plant removal.
In general, effective chemical control requires multiple applications. Timing and application rate are crucial for successful control. Always read the label when applying an herbicide. The herbicides Escort (metsulfuron) or Telar (chlorsulfuron) are very effective and do not kill grass. The optimum time to apply Escort and Telar for hoary cress control is in the spring when it is flowering or in the fall. Telar can be purchased in small amounts (2 oz) at Cropworx or Paonia Farm and Home for about $48.00. Two ounces is enough for about 1.5 acres. Glyphosphate (Roundup) also works, but it kills all surrounding vegetation.
There are no effective biological agents for whitetop at this time but research in this area is ongoing. Whitetop is in the mustard family which increases the difficulty of finding control agents that won't attack desirable food species.