Biology and Management of Benghal Dayflower (Commelina benghalensis) in Ornamental Crop Production

Benghal dayflower is listed among the world’s worst weeds, affecting over 25 crops in 29 countries (Holm et al., 1977). Benghal dayflower has many characteristics that make it a very troublesome weed in Florida landscapes, nurseries and other agricultural production areas. It was first recorded in Florida in 1928 and was designated as a legally noxious weed by the U.S Department of Agriculture in 1983 (Faden, 1993). Due to its status as a legally noxious weed, presence of benghal dayflower on nursery property can lead to quarantines, so identification and management is critical for nurseries. This 5-page article is written for green industry professionals and others to aid in the identification and management of benghal dayflower in and around ornamental plants. Major revision by Yuvraj Khamare, Chris Marble, and Robert Stamps, and published by the UF/IFAS Environmental Horticulture Department. Previous version: Stamps, Robert. 2011. “Prevention, Early Detection, and Eradication of Benghal Dayflower in Field Nurseries”. EDIS 2011 (5/6). https://journals.flvc.org/edis/article/view/119299.

Potential of two cover crops, signal grass and ruzi grass: suggested allelopathic effect on some important weeds

There is evidence that signal (SG) and ruzi (RG) grass have an allelopathic effect on weeds. This study aim to evaluate this effects on difficult-to-control weeds: hairy beggarticks (HB), benghal dayflower (BD), horseweed (H), sourgrass (S) and tall windmill grass (TWG). The first experiment was installed in a completely randomized design with 2 donor species (SG and RG) × 4 extract concentrations (0, 75, 150 and 225 mg ml−1) in factorial scheme with four replicates. Weed germination percentage was evaluated in three-day intervals. In the second experiment, the weeds emerged in substrates previously cultivated with SG and RG, in completely randomised block design with four replicates. The emergence, shoot growth and root growth were evaluated. The results were as follows: (i) on horseweed (H), 84% germination inhibition by RG leaf extracts and 38% emergence inhibition by SG root exudates were observed; (ii) on benghal dayflower (BD), 84% germination inhibition by RG leaf extracts and 37% emergence inhibition and 4.3 times the SRL values than control by RG root exudates; (iii) on hairy beggarticks (HB) 52% germination inhibition by RG leaf extracts scored, while SG root exudates reduced 43% of the emergence, 24% shoots biomass accumulation and 11.3% root length; (iv) on sourgrass (S) 71% germination inhibition by both donor plants and 75% germination inhibition by RG leaf extracts were measured. Finally, on tall windmill grass (TWG) 69% germination inhibition was observed upon using both donor plants. It can be concluded that foliar allelochemicals inhibit the germination of: BD > S > TWG > H > HB, while root exudate allelochemicals, inhibit the emergence and root development of all weeds

In vitro clonal propagation and evaluation of antibacterial activity of Benghal dayflower-Commelina benghalensis L.

An efficient protocol for in vitro propagation of Commelina benghalensis was developed. Nodal segments were showed the superb explants in performance for shoot proliferation than other explants. On the other hand, BAP with auxin was better combination. The maximum (90.52) number of explants response and the highest (23.25) number of shoots per plant were obtained from nodal segments on MS medium fortified with 3.0 mg/l BAP+0.1 mg/l IBA. The highest shoot length (17.25 cm) was achieved on MS medium containing 3.0mg/l BAP+0.5mg/l IBA. In vitro proliferated shoots were transferred to full and half strength of MS media where 1.5 mg/l IBA on full strength of MS media was the best to fit for the maximum number (12.69) of roots formation per micro-shoot. Well rooted plantlets were transferred to soil and successfully acclimatized with 97% survival rate. Three extracts i.e. methanol, ethanol, Petroleum ether of C. benghalensis L and four concentrations of each extracts were used against five gram (+ve) and five gram (-ve) bacterial species for the screening of antibacterial activity. Ethanol extracts was the superior in performance. The susceptibility of tested pathogenic bacterial species was increasing compare with increasing of extracts concentration with few exceptions. The highest zone of inhibition was obtained against S. aureus (17.50 mm) and P. aeruginosa (17.44 mm) at 800 mg/l dose level of extracts. It was also noticed that Gram (+ve) bacterial species are more susceptible to Benghal dayflower crude extracts than Gram (-ve) bacterial species.

Benghal Dayflower/Tropical Spiderwort (Commelina benghalensis L.) Identification and Control

This 3-page document provides an overview of tropical spiderwort identification and control. Written by J. A. Ferrell, G. E. MacDonald, and P. Devkota, and published by the UF/IFAS Agronomy Department, revised May 2020.

EFFICACY AND SELECTIVITY OF HERBICIDES APPLIED IN CASSAVA PRE-EMERGENCE

ABSTRACT The interference imposed by weeds can cause damages to cassava development. Thus, adopting control measures is fundamental. The use of pre-emergence herbicides is one of the control alternatives, since cassava presents a good tolerance to herbicides applied in this modality. However, herbicides may present differential selectivity due to the variety of cassava that is planted. The objective of this study was to evaluate both weed control effectiveness and selectivity of different herbicide combinations applied at pre-emergence of two cassava varieties. Two experiments were established in the field using a randomized complete block design, in a split plot scheme, with four replications. In the efficacy experiment, application of six combinations of herbicides, including clomazone + ametryn, clomazone + metribuzin, clomazone + flumioxazin, isoxaflutole + ametryn, isoxaflutole + metribuzin, isoxaflutole + flumioxazin were evaluated in the main plot. In addition, a non-treated control and a weeded control were evaluated. In the subplots, the Caravela and Pretinha varieties were planted. For the selectivity experiment, a non-treated control was not included. The combinations containing clomazone presented a longer residual period of weed control as well as a better control of benghal dayflower. Metribuzin exhibited lower efficacy than other herbicide combinations containing clomazone or isoxaflutole. The Pretinha variety showed greater tolerance to weed interference. Every herbicide combination that was applied in cassava pre-emergence presented selectivity for both Caravela and Pretinha varieties.

Anatomy and Pollination of Cleistogamous Flowers of Benghal Dayflower (Commelina benghalensis)

The anatomy and pollination of subterranean cleistogamous flowers of Benghal dayflower (Commelina benghalensis) is described as a contribution to understanding its reproductive biology. Subterranean stems bear one spathe per node, each enclosing a single cleistogamous flower. Only the three anterior stamens produce functional pollen; the posterior three stamens are staminodes. Tapetum is amoeboid and endothecium is present. The three-carpellate superior ovary bears five dimorphic orthotropous ovules. Nearly mature flowers have straight to somewhat curved styles; at maturity, styles elongate and coil. Our observations indicate that coiled style growth causes rupture of anthers and brings pollen into contact with stigmas. Pollen tubes were observed in styles that had previously undergone coiling, located within mucilaginous secretions of the mature stylar canal. The subterranean cleistogamous flowers of Benghal dayflower and their apparently unique mode of pollination, viewed together with reproductive capacity of its aerial chasmogamous flowers, underscore the complexity and flexibility of the reproductive biology of this noxious weed species.

Environmental Influences on Growth and Reproduction of InvasiveCommelina benghalensis

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 ofC. 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 aboveground 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. benghalensisplants 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 that (1) fertility management in highly weathered soils may strongly constrain competitiveness ofC. 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 byC. benghalensiswill likely cause continual persistence problems in agricultural fields.