Environmental influeneces on growth and reprodcution of invasive Commelina benghalensis

Authors: RIAR, M - North Carolina State University; CARLEY, D - North Carolina State University; ZHANG, C - North Carolina State University; SCHROEDER-MORENO, M - North Carolina State University; JORDAN, D - North Carolina State University; Webster, Theodore; RUFTY, T - North Carolina State University

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2016
Publication Date: 2/1/2016
Citation: Riar, M.K., Carley, D.S., Zhang, C., Schroeder-Moreno, M.S., Jordan, D.L., Webster, T.M., Rufty, T.W. 2016. Environmental influeneces on growth and reprodcution of invasive Commelina benghalensis. International Journal of Agronomy. Vol. 2016, Article ID 5679249, 9 pages, 2016. doi:10.1155/2016/5679249.

Interpretive Summary: Benghal dayflower is among the world’s worst weeds in agricultural systems, with infestations occurring in 25 crops in 29 countries. In the U.S., it became established in Florida in the early1930s, and is now moving northward. The prevalence in Georgia has led to challenges with Benghal dayflower control in cotton and peanut production, as infestations have commonly caused 60% to 100% yield reductions. A key to Benghal dayflower invasiveness is its reproductive flexibility. In its native geographical areas (i.e. tropical Asia, Africa and the Pacific Islands), Benghal dayflower grows as a perennial, but it can survive as an annual in temperate regions. It is fast growing and a prolific seed producer. Both aerial and subterranean seeds are produced in dimorphic flowers, and seeds have variable dormancy and germination characteristics. Furthermore, Benghal dayflower has the ability to regenerate from stem fragments. These characteristics, plus a high degree of tolerance to glyphosate, make Benghal dayflower exceptionally difficult to control in agronomic systems when it becomes established. Much is unknown about how the invasive weed Benghal dayflower interacts with the environment. Benghal dayflower competitiveness and reproduction are strongly increased by the high nutrition typically used with grain crops. A valid containment strategy with large infestations of Benghal dayflower would be to grow a series of crops with low or no added nitrogen fertilizer, like soybean or an N2-fixing pasture. It should be emphasized that substantial growth and especially reproductive output still occurred at lower nutrition in our experiments, so it is anticipated that a degree of weed pressure will persist. Vegetative growth of Benghal dayflower is suppressed under short days, even when flowering shifts only a few days. Thus, Benghal dayflower competitiveness is likely to be reduced when germination and growth occur during shorter photoperiods outside of normal crop growing seasons, even though high temperatures may become more prevalent. A third observation is that, regardless of the type of environment, Benghal dayflower exhibits a substantial reproductive capability, and this is true even when vegetative growth is suppressed by nutrition, low light, or a photoperiod shift. Underground reproduction appears to be particularly resilient. The persistent reproductive output underscores the importance of intensive management strategies to prevent introduction of Benghal dayflower into agricultural fields.

Technical Abstract: Commelina benghalensis (Benghal dayflower) is a noxious weed that is invading agricultural systems in the southeastern United States. We investigated the influences of nutrition, light, and photoperiod on growth and reproductive output of C. benghalensis. In the first experimental series, plants were grown under high or low soil nutrition combined with either full light or simulated shade. Lowered nutrition strongly inhibited vegetative growth and above ground spathe production. Similar but smaller effects were exerted by a 50% reduction in light, simulating conditions within a developing canopy. In the second series of experiments, C. benghalensis plants were exposed to different photoperiod conditions that produced short- and long-day plants growing in similar photosynthetic periods. A short-day photoperiod decreased time to flowering by several days and led to a 40 to 60% reduction in vegetative growth but reproduction above and below-ground was unchanged. Collectively, the results indicate 1) fertility management in highly weathered soils may strongly constrain competitiveness of C. benghalensis; 2) shorter photoperiods will limit vegetative competitiveness later in the growing seasons of most crops; and 3) the high degree of reproductive plasticity and output possessed by C. benghalensis, will likely cause continual persistence problems in agricultural fields.