Weed of the month: Burcucumber (Sicyos angulatus), An Agronomic Pest on the Increase

Published: September 23, 2014

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.

Figure 1: Burcucumber grows as a vine; these vines are increasingly being found in agronomic fields, competing with and climbing soybean and corn.

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.

Figure 2: Burcucumber seedling emerges from soil. The cotyledons are thick and oblong.

Figure 3: Burcucumber uses tendrils to climb up objects, or in this case another plant, to reach sunlight.

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.

Figure 4: The leaves of burcucumber are broad, hairy, and have 3 to 5 lobes.

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.

Figure 5: The burcucumber fruits are small, similar to miniature cucumbers, grow in clusters, and have spines covering the surface.⁵

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

• ¹Childs DJ, Jordan TN, and RL Blackwell. (1996) Survey of problem weeds in Indiana.  Purdue University Cooperative Extension Service.  WS-10.
• ²Johnson Q, and M VanGessel. (2012) Burcucumber control in cropland.  University of Delaware College of Agriculture and Natural Resources Weed Facts WF-4.
• ³Esbenshade WR, Curran WS, Roth GW, Hartwig NL, and MD Orzolek. (2001) Effect of tillage, row spacing, and herbicides on the emergence and control of Burcucumber (Sicyos angulatus) in soybean (Glyince max).  Weed Technology 15:229-235.
• ⁴Nice G, Johnson W, and T Bauman. (2005) Identifying and controlling Burcucumber.  Purdue Extension Weed Science: www.btny.purdue.edu/weedscience/
• ⁵Mohlenbrock RH. (1989) Midwest wetland flora: Field office illustrated guide to plant species (hosted by the USDA-NRCS PLANTS database).  Midwest National Technical Center, Lincoln, NE.