The issue: Common crupina
Common crupina (Crupina vulgaris) is a winter annual from Eurasia. After overwintering as a rosette, the flowering stems bolt in the spring, grow up to 4 feet tall, and have many branches. It tolerates a wide range of soil, temperature and moisture regimes. It is found in deep canyons, on south facing slopes, grassy sites, pastures, rangelands, neglected areas and roadsides.
The lower leaves have toothed margins and become increasingly lobed as you go up the stem, giving way to finely divided leaves that have no petiole in the upper areas. It belongs to the knapweed family and the lavender to purple flowers are similar to other knapweed flowers.
Common crupina reproduces only by seed that may remain viable up to three years in field conditions. Preventing seed production is essential for control. Seeds may spread through water movement, the digestive tracts of many animals, or in contaminated seed and hay.
Integrated pest management options:
· Prevention: Keep ditch banks free of seed-producing weeds; feed weed-free hay; always be on the lookout for new weed infestations.
· Mechanical: Cultivate before flowering; hand-dig small patches before flowering; bag and discard any flowering plant parts; remove roots at least two inches below the crown; repeat as needed throughout the season.
· Cultural: Don’t overgraze pastures; manage land to provide good competition from desirable plants; revegetate disturbed areas.
· Biological: None.
· Chemical: Apply in fall or early spring before blooming—plants treated after bloom may still produce seeds; 2,4-D, dicamba, picloram (restricted use herbicide), glyphosate, clopyralid, or metsulfuron. Be sure the weed and landscape or crop situation are listed on the label. Always read and follow herbicide label directions.
Combine different IPM options over a period of years to help improve the effectiveness of your efforts.