Field Scouting Guide: Morning Glory
The latest entry to American Vegetable Grower‘s Field Scouting Guide concentrates on Convolvulus arvensis (field bindweed or morning glory vine).
We’ve reached out to experts to learn how to spot and treat this weed. This month, our contributors are Lynn M. Sosnoskie, University of California Agriculture and Natural Resources, and Timothy W. Miller, Washington State University.
- Scientific name: Convolvulus arvensis
- Common name: Field bindweed or morning glory
- Geographical Range: Native to the Mediterranean, worldwide distribution, including temperate, tropical and Mediterranean regions.
- Crops affected: Many, worldwide. It also impacts other disturbed habitats like railroads and right of ways, fencerows, etc.
Sosnoskie: The species has been reported in almost every county in California. In California’s Central Valley, processing tomatoes and newly planted orchards can have significant issues with the species.
There haven’t been any formal economic analyses done recently (at least not in California), but we do know that the vine in an annual cropping system can reduce yields. Some processing tomato growers have told me they have not harvested fields or parts of fields with severe infestations. I’ve also seen yield reductions in cotton intolerant to glyphosate. In addition to yield loss, there is the cost associated with managing the species (such as herbicides and labor).
Since this perennial weed persists over seasons, it’s a recurring problem. The vines actively grow in the spring and summer. And that’s when they are most likely to interfere with crops, either by competing for water, nutrients, and light, and/or by physically growing over/on top of the crops.
Miller: Identifying field bindweed is fairly easy. It’s an herbaceous perennial, meaning that stems die back annually to a perennial crown and root system.
Stems. The twining stems are very numerous, with each crown producing several stems. Vines lie flat on the ground until they find something to wrap around, after which they may achieve lengths of 5 feet or more.
Leaves. Leaves are about 1 inch long and are shaped like arrowheads, with pointed to rounded tips and two short basal lobes that flare outwards or downwards.
Flowers. From the axils of these leaves arise the pretty funnel-shaped flowers, also about an inch wide at the opening. Petals are fused together, and are pure white to pink, often looking like little peppermint candies among the leaves. Each flower stem bears two tiny bracts about an inch below the funnel.
HOW IT SPREADS
Miller: Field bindweed spreads in two ways: from seeds and from the creeping roots. Most flowers produce four seeds, rough-textured, 4 mm long by 3 mm wide, and gray-brown in color. Seeds germinate best under warm temperatures (70°F to 85°F) and the hard seed coat induces a level of dormancy, which may be as long as 50 years in the soil.
Once established on site, the root system is the main means of spread. Roots may be as much as 20-feet deep, producing many lateral roots, leading to new crowns at the surface. Fragments of stems and roots resulting from cultivation freely root and produce shoots.
Sosnoskie: For more information about the biology and ecology, visit my article on the University of California, Riverside’s blog.
Sosnoskie: Systemic herbicides, like glyphosate, are probably the go-to tools for control of field bindweed in non-crop areas, prior to planting, in tree and vine systems, and in Roundup Ready agronomic systems.
Physical disturbances, like cultivation or tillage, can be used to manage field bindweed but must be carried out repeatedly. Infrequent cultivation can actually make infestations worse. That’s because rhizomes spread through the field and new vines can establish from the fragments.
Some soil-applied herbicides (like trifluralin) are available that can suppress the vines in some annual cropping systems short term. Long-lasting dormant seeds can survive for decades in the soil, so you should know infestations can return even if you make efforts to eradicate near-surface roots and rhizomes.
The recommendations for traditional chemistries will depend on the system you are working in. Please see the Pacific Northwest Extension publication on bindweed for examples.
Miller: I’d add that Roundup or other glyphosate products have very good activity when applied to foliage, but few crops allow a grower to use that herbicide during the summer due to concerns with crop safety (the twining nature of the plant means that weed and crop leaves are often clustered together. Row middles, however, often can be treated with foliar glyphosate from a shielded sprayer, which will help slow down the field bindweed. Wipers also may be helpful, although again the twining stems may wrap around the crop plants and make selective application difficult or impossible.
RECOMMENDED IPM METHODS
Sosnoskie: IPM recommendations should focus on choosing to plant into fields that are free from bindweed. If this is not possible, manage field bindweed as well as possible prior to planting sensitive crops (by using effective herbicides in rotational crops or by actively targeting the weed in fallow periods). Use all available tools (cultivation, herbicides) to suppress the vine, in crop. Hand weeding and mowing are not particularly effective due to the prostrate nature of the species. Whatever strategies are employed, repeated applications/efforts will be needed because of the perennial nature of the weed.
Miller: I’d also add that plastic mulches can aid in control of the weed in vegetables. Field bindweed shoots are not sharp-tipped, so bindweed stems will generally only grow from planting holes or from outside the edge of the mulch. This can localize the weed a bit, making foliar herbicide applications a little more selective. Soil fumigation can also be helpful, reducing the number of viable roots from which new shoots can emerge.