ISSUE 12 July 26, 2007
WHITE COCKLE QUESTIONS
White cockle is a persistent weed in hayfields and no-till fields and it seems to be an increasing problem based on recent questions. Here are a few key points about white cockle and some management comments.
1. White cockleís name is officially white campion, but you will most likely still see it as white cockle on some herbicide labels if it is listed.
2. White cockleís life cycle is a biennial or short-lived perennial. It grows from the same crown and does not spread by roots. It is very successful in establishing from seed that germinates in either spring or fall.
3. Identification: White cockle seedlings are yellowish-green and soon grow into a rosette with opposite leaves with soft hairs. As plants get older, they may have a grayish-green color because of the hairs. The opposite leaf arrangement is easier to see on the stems that produce the showy white flowers. Flowers have 5 notched petals.
Odd fact: White cockle plants have either male or female flowers. The female flowers swell and develop into the familiar round seedpods.
Important fact: White cockle, like many other weeds in the pink family, is not very sensitive to 2,4-D. Therefore, 2,4-D used alone in burndown treatments or 2,4-D used for weed control in winter wheat is not effective unless mixed with another herbicide.
Management: White cockle generally is not a problem in spring-tilled fields. In no-till fields, herbicides are generally most effective in the fall. In particular, glyphosate will be more effective in the fall and should be used at a minimum of 0.75 lb ae/a (i.e. the old 1 quart rate). In the spring, glyphosate will give good suppression at this rate, but control may not be complete. The addition of Valor to glyphosate in the spring may increase glyphosateís control of existing plants. Valorís residual activity will help to control emerging seedlings. Research has shown success in controlling white cockle in the spring with Gramoxone plus Sencor on a warm, sunny day, but only had good suppression on a cooler, cloudy day. Sencor helps Gramoxone by synergizing the Gramoxone. Sencorís residual activity also helps to control emerging seedlings.
If white cockle is not controlled before crop planting, many of the plants will likely be starting to or flowering by the time postemergence applications are made. In Roundup Ready soybeans or corn, glyphosate can be used to suppress these plants. However, no herbicide will control white cockle adequately in conventional soybeans. In corn, dicamba-based products (i.e. Banvel, Clarity, Distinct, Status) should suppress larger plants and kill seedlings. A preemergence application of atrazine should also prevent white cockle from emerging in corn in the spring.
Overall, it is probably best to scout fields that might have white cockle in the fall. These fields might be those that previously had cockle or are hay fields going to corn or soybeans. If white cockle is found, a fall treatment of glyphosate should remove many plants and limit the problem the following spring. Also, plan programs that control spring seedlings by using either a residual preemergence herbicide or an effective postemergence herbicide. Otherwise, these little seedlings will develop into the rosettes that are more difficult to control in the fall or the next year.
SUPPLEMENTAL LABEL FOR ROUNDUP PREHARVEST APPLICATION IN SUNFLOWER
Monsanto has issued a Supplemental label allowing certain applications of Roundup for control of annual and perennial weeds in sunflower and safflower.
Registered applications include: Chemical Fallow, Preplant Fallow Beds, Preplant, Preemergence, At-Planting, Hooded Sprayers in Row Middles, Shielded Sprayers in Row Middles, Wiper Applications in Row Middles, Preharvest, and Post-Harvest treatments.
In safflower, apply no more than a total of 2 quarts of the 4.5 ae/gal formulations at preharvest. In sunflower, apply no more than a total of 22 fl oz of the 4.5 ae/gal formulations at preharvest.
For preharvest, apply for weed control, NOT crop desiccation when crop plants are physiologically mature. For sunflower, apply when the backsides of sunflower heads are yellow and bracts are turning brown and seed moisture is less than 35%. For safflower, apply when seed has lost the opaque character, approximately 20 to 30 days after the end of flowering of the secondary branches. For sunflower, apply when the backsides of sunflower heads are yellow and bracts are turning brown and seed moisture is less than 35%. Allow a minimum of 7 day PHI for both crops.
For post-harvest weed control. The products may be applied after harvest of safflower or sunflower. Higher rates may be required for control of large weeds, which were growing in the crops at the time of harvest. Tank mixtures with 2,4-D or dicamba may be used.
FIELD BINDWEED MITES?
I received some calls about field bindweed mites. The following is a response from Dr. Rod Lym, NDSU Perennial/Noxious Weed Scientist.
These mites have been around since the late 1980's (Aceria malherbae). They are not very effective and at most keep the plant from flowering and stunt the growth for at least a portion of the season. They do not establish well in cropland or anywhere herbicides are also used. I consider them pretty much ineffective in control.
Individuals can contact the APHIS office in Bismarck if interested in getting them.
NDSU Extension Weed Specialist