Burcucumber, is a summer annual weed that resembles the cultivated cucumber. Currently, burcucumber can be found from the east coast to as far as west as Minnesota, Kansas, and Texas, and is becoming an increasing problem in agronomic crops. This climbing vine is recognized as a noxious weed in Delaware and Indiana, and in the latter state it is considered one of the 10 most difficult-to-control weeds in soybean1.
Predominantly found in low-lying areas and near creeks and rivers, burcucumber can also become a problematic weed in agronomic crops. Burcucumbur seed can germinate in a range of soil temperatures (from 60 to 95°F2), and can germinate into the later months of the growing season, after herbicide applications are typically applied. Because the weed grows as a vine (Figure 1), the plant can compete with corn and soybean late in the season.
When grown in direct competition with soybean, burcucumber can reduce yield by up to 48 percent3 and the weighty vines of this weed can lodge corn4.
When burcucumber emerges, the seedling’s cotyledons are thick and oblong (Figure 2), similar to the cultivated cucumber. The hypocotyl, or stem below the cotyledons, is covered with many short hairs that point downward. The plant has a fibrous root system and uses branched tendrils (thin coiled appendages along the stem that are similar to what is found on peas) to move up surfaces in search of sunlight (Figure 3).
The leaves are in an alternate pattern along the stem, and are 2 to 8 inches long and wide. The leaves are hairy, broadly heart-shaped, and generally have 3 to 5 pointed lobes and a toothed margin (Figure 4). Burcucumber stems are also hairy, especially at the leaf nodes. These hairs are one of the main differences between burcucumber and wild cucumber (Echinocystis lobata), which has a stem that usually lacks hairs.
The burcucumber flowers are usually whitish with a green tint and have 5 petals. The fruit are produced in clusters of 3 to 20 and resemble small cucumbers (about ½ to ¾ inches long and ¼ inch thick) that are covered with bristles/spines (Figure 5).
Due to the ability of this weed to germinate throughout the corn and soybean growing season, burcucumber can be a challenging pest to eliminate. While foliar-applied herbicides can control current flushes, herbicides with residual activity can help minimize flushes of burcucumber that may occur later in the season.
In corn, pre-emergence (PRE) applications of atrazine or atrazine-containing pre-mixes will provide early-season control, but a post-emergence (POST) herbicide application will usually be necessary. Weed scientists at Penn State University have found that two and three-way mixes of products like Lexar or Corvus + atrazine in corn are some of the more effective PRE treatments that can reduce the density and size of burcucumber plants by the time of the POST application. Beacon (primisulfuron) and products that contain this active ingredient, dicamba-containing products (Banvel, Clarity, Distinct, Marksman, Status, etc.), Callisto and products that contain this active ingredient, Liberty, and glyphosate products (Roundup, Touchdown, etc.) are all effective POST treatments in corn.
In soybean, there are a variety of PRE treatments that will provide initial suppression and reduction in the burcucumber population, but similar to corn, a POST treatment will almost always be required. Effective PRE herbicides for burcucumber include products that contain chlorimuron (Authority XL, Authority Maxx, Envive, Valor XLT, etc.) or imazethapyr (Pursuit, Authority Assist, etc.), and these treatments must be followed by an effective POST treatment such as Classic, Liberty (Liberty Link soybean only), glyphosate, or Synchrony STS (STS soybean only).
For more information on burcucumber and other challenging weeds, please visit our Web site at: weedid.missouri.edu
REVISED: September 30, 2015