Bur cucumber is a summer annual vine that is extremely aggressive. It can easily take over fields and cause large yield reduction as the vine can grow 15-25 feet long. This weed is becoming a serious agronomic issue in corn and soybean fields around our area.
Bur cucumber is part of the Cucurbitaceae or melon family. The leaves are close to circular in shape with 3 to 5 lobes. This plant produces both male and female flowers throughout the summer and dies at the first frost. The fruits produced are yellow in color, covered with prickly bristles, and are found in clusters of 3 to 10. Bur cucumber is normally found in damp soils, along wetlands, roadsides, or fence lines but recently have been found causing problems in agricultural fields, especially in no-till situations.
The seeds of this vine are viable in the soil for many years due to the hard seed coating. It is very easy to spread to uninfected areas. There is not one single way to control this weed, as its increased dormancy and growth habit makes it almost impossible for eradication. A combination of several control methods; cultural, mechanical, and chemical; may be the best way to control bur cucumber.
Mechanical control, including tillage and cultivation, may break up the vine and bury the seed deep enough to prevent germination. When tilling fields, it is important to make sure your equipment is clean and you are not transporting the vines from one field to the next, as this weed can easily get wrapped around equipment. It is almost important that during the season you do not drive through this weed and transport it to other, uninhabited areas. Even though bur cucumber is increasing in no-till fields, it may be beneficial to leave these fields under the no-till system. This will allow for the seeds to remain close to the surface and increase the efficacy of chemical control. However, depending on your management strategies, this option may not work for you.
Cultural control includes selecting aggressive crops that are competitive early in the season such as alfalfa or small grains. Maintaining adequate soil fertility is also critical in managing for bur cucumber. If the weed has gotten into your corn fields, it may be best to harvest the infected areas for silage to reduce the viability of the seed.
Chemical control mixed with the other methods may be the best way to control this weed. However, this control is reliant on the weather conditions. There have been some herbicides that have controlled bur cucumber well, especially those with a good residual. Pre-emergent herbicides can be used, but again the weather will determine how well the herbicide will work. Post-emergent herbicides have shown to best control bur cucumber. Herbicides with Dicamba as the active ingredient have been shown to provide decent control. Glyphosate products can be effective as well but must be used while the plant is still young to provide adequate coverage and control. Penn State has done some research on herbicide mixtures for controlling bur cucumber in corn, soybeans, and small grains. Triazine herbicides have also shown good short season control but may require subsequent applications or cultivation. If using post-emergent herbicides, it is recommended to spray at the appropriate stage in crop development but also target the vine before it reaches 12 inches long to get better control.
It is important that we get ahead of this weed for the coming growing season, as we don’t want to allow it to continue spreading. Proper control and scouting is important for controlling bur cucumber.
For complete Penn State herbicide trial results, see https://extension.psu.edu/managing-burcucumber-in-agronomic-crops.
Cassidy Fletcher, Northeast Sales Agronomist, and Technical Lead.