Burcucumber and toothed spurge, two weeds to watch for in 2015

Tuesday, January 13, 2015

At the MU Extension Crop Management Conference, Kevin Bradley, University of Missouri weed scientist, indicated that producers should lookout for two emerging weed pests in 2015. These weeds are burcucumber and toothed spurge.

Burcucumber has the potential to reduce yields by as much as 48 percent. Burcucumber is a summer annual and resembles the cultivated cucumber. It has tendrils for climbing and sticky hairs and is predominately found in low-lying areas and near creeks and rivers. It can be found from the east coast to as far west as Minnesota, Kansas and Texas, and is becoming an increasing problem in agronomic crops. It is recognized as a noxious weed in Delaware and Indiana, and in Indiana, it is considered one of the 10 most difficult-to-control weeds in soybean.

Burcucumber seed cam germinate in a range of soil temperatures (from 60 to 95 degrees F) and can germinate into the later months of the growing season, after herbicide applications are typically applied. Because the plant grows as a vine, the plant can compete with corn and soybean late in the season. Due to the ability of this weed to germinate throughout the corn and soybean growing season, burcucumber can be difficult to control. Foliar applied herbicides can control current flushes, herbicides with residual activity can help minimize flushes of burcucumber that may occur later in the season.

The second weed of concern is toothed spurge. The toothed spurge is another summer annual that is appearing in northwestern Missouri. According to Bradley, it is often incorrectly referred to as a wild poinsettia and is not considered a common weed yet, but one that has increased in prevalence over the past several seasons, especially in Missouri soybean fields.Toothed spurge can also be found in pastures, along roadsides and in other non-crop areas.

Toothed spurge can grow up to 2 feet tall and has light green to reddish green stems with short hairs. The leaves and stuns emit a white milky sap when broken. The sap produces blisters and dermatitis in humans, cattle and horses and caused blindness if it comes in contact with the eye.

Toothed spurge is tolerant to normal use rates of glyphosate. The appearance of toothed spurge is an example of weed shift. After continuous application of the same herbicide, in this case glyphosate for post-emergence weed control needs, species that are naturally tolerant of that herbicide are most likely to appear in that cropping system and become more prevalent. Also, toothed spurge does not typically emerge until later in the season and escapes the residual effects of many pre-emergence residual herbicide treatments.