|In This Issue|
|A Wedge-Shaped Wonder|
|Farm Bill Update|
Changes in production schemes may cause a resurgence of this weed
Benghal dayflower, also known as tropical spiderwort, is a weed that came on the row-crop production scene in the early 1990s. As production schemes changed, particularly with the use of different herbicides, producers found better control of this weed. Now, with yet another shift, it looks like this weed may make a resurgence in the field. Therefore, a recap on this problem weed is in order.
Benghal dayflower is an aggressive weed that produces both above-ground and below- ground flowers and viable seed. It possesses the ability to root at the nodes and can be propagated from cut stems. Light cultivation often breaks the plant apart and increases the infestation area.
Although benghal dayflower is difficult to control, early identification and proactive management can greatly reduce its impact on crop yields.
Benghal dayflower has often been confused with spreading dayflower (Comellina diffusa) and Asiatic dayflower (C. communis). However, three characteristics separate benghal dayflower from the other dayflowers: 1. Presence of leaf hairs; 2. Purple or lavender color flowers; 3. The presence of underground flowers, which appear as “swollen nodes.”
Current crop production practices, such as minimum tillage, encourage greater germination and growth of this weed. However, another observation is that benghal dayflower grows poorly in low-light environments. Knowing this, using earlier planting dates to form a dense crop canopy prior to weed germination can suppress benghal dayflower growth and establishment.
Planting in twin rows is another cultural practice that helps establish rapid coverage of the soil surface and may interfere with weed seed germination and emergence.
Controlling benghal dayflower in peanuts will require multi-step management practices that include both cultural practices and herbicides.
A successful herbicide program involves an early season application of Dual Magnum. Preemergence applications of Dual Magnum are not as effective.
Data collected in Florida and Georgia have shown that Gramoxone Inteon at eight ounces per acre plus Dual Magnum at 1.33 pints per acre will provide approximately 90 percent control when applied at-cracking. Gramoxone Inteon plus Dual Magnum may be applied up to 28 days after cracking, but early applications at seven to 14 days after cracking will generally provide better weed control and reduce peanut injury.
Strongarm herbicide has also proven effective at controlling or suppressing benghal dayflower growth. However, consult the product label as to availability in your state.
Early Control Is Key
Benghal dayflower control from midor late-season herbicide applications have proven to be inconsistent and are directly related to weed size at time of treatment. Cadre or Classic plus 2,4-DB can provide some control if applied when benghal dayflower is small. However, these herbicides should be used as part of a control program that contains Gramoxone plus Dual Magnum.
In cotton, Roundup-based programs developed to control Palmer amaranth have indirectly controlled benghal dayflower very effectively. However, more recently, it has been observed that with the greater adoption of Liberty-based programs, benghal dayflower became more problematic as Liberty is not effective in controlling this weed.
Benghal dayflower is a highly competitive and difficult-to-control weed that may be making a comeback in fields, that is, if it ever left. Effective control can often be attained if early scouting, cultural and herbicidal management schemes are implemented. In extreme conditions, deep tillage may be helpful, but only if herbicide and cultural management programs have proved ineffective. PG
For more information, consult “Benghal dayflower (Commelina benghalensis, L.) Identification and Control,” by J. A. Ferrell, G. E. MacDonald and R. Leon at edis.ifas.ufl.edu/ag230, or “University of Georgia Herbicide Programs for Tropical Spiderwort (Benghal Dayflower) Control in 2013 Cotton,” by A. S. Culpepper, J. T. Flanders and T. M. Webster at the Web address www.caes.uga.edu/Publications and search for publication C-923.