Velvetleaf Plants Research Articles

Interaction of a bioherbicidal fungus with a phenoxy herbicide for controlling velvetleaf (Abutilon theophrasti)

ABSTRACT The fungus, Fusarium lateritium Nees ex Fr. (FL), has shown potential as a bioherbicide for velvetleaf (Abutilon theophrasti Medik.) control. However, to achieve optimal infection and weed mortality, bioherbicide applications must be applied to weeds that are in the cotyledonary growth stage, followed by a dew treatment of at least 16 h. Greenhouse and field experiments were established to discover possible synergistic disease interactions with a phenoxy herbicide to improve the bioherbicidal potential of this fungus, and to mitigate some of the physical and environmental restrictions that limit the utility of this fungus as a bioherbicide. In greenhouse experiments, mortalities of 94% and 94% were recorded from sequential applications of 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] (0.02 kg ae ha−1) followed by FL (1.5 × 106 spores ml−1) at 5 min or 7 days after herbicide treatment. Velvetleaf plants in the fifth-to-seventh leaf growth stage were infected and killed with < 8 hrs. of dew. Similar results occurred under field conditions. Infection and weed control were inhibited by tank mixtures of 2,4-DB and FL, and by sequential applications of FL followed by 2,4-DB. These results suggest that timely applications of 2,4-DB followed by F. lateritium may provide effective control of velvetleaf.

Total Polyphenols and Antioxidant Activity of Yellow Velvetleaf (Limnocharis flava) Extract

An increase in free radicals can cause damage to cells and tissues in the body. This is caused by a lack of antioxidant ability in the body, so it requires antioxidants outside the body. One of the plants that can be used as a source of antioxidants is the yellow velvetleaf (Limnocharis flava), which has a class of polyphenolic compounds. The crude extract of this plant still has other components that are not included in the polyphenol compound. This study aimed to measure the total polyphenol and flavonoid contents as well as the antioxidant activity of the yellow velvetleaf plant (L. flava) before and after purification. The purification process is carried out using the solid-phase extraction method. The antioxidant activity was determined by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The total polyphenol and flavonoid contents increase after the purification process. Therefore, the antioxidant activity of purified extract is also increased when compared to crude extract. These results show that the purification process successfully increased the levels of polyphenol compounds from the yellow velvetleaf plant and its antioxidant activity. Thus, the purified extract can be used as an alternative source of natural antioxidants and can be developed as a food supplement ingredient.

Effects of fertilizer treatment on the polyphenol content in maize and velvetleaf competition

The aim of this research was to examine the effect of fertilizer treatment on the content of polyphenols in velvetleaf and maize, grown without use of herbicides under controlled conditions (12h/12h, T 25?/22?C day/night). Plants were treated with organic - F1 and synthetic fertilizers - F2 and F3. The content of total phenols, individual polyphenolic acids and antioxidant activity of plant extracts were examined, as important indicators of the plant condition and its resistance to oxidative stress. The content of total phenols was determined spectrophotometrically (modified Folin-Ciocalteu method). The content of individual polyphenolic acids was determined by the high-performance liquid chromatography method, while measurement of polyphenols antioxidant activity was determined by the DPPH method. It was established that in maize, the application of fertilizers, neither in monoculture nor in competition with velvetleaf plants, caused statistically significant changes in the content of polyphenolic acids. However, in velvetleaf, the use of fertilizers led to an increase in the content of polyphenolic acids in conditions of competition vs monoculture. The content of chlorogenic, p-coumaric and trans-ferulic acids was statistically, significantly higher in plants of velvetleaf competition vs monoculture, and the content of chlorogenic, p-coumaric and cinnamic acids was lower in plants of maize competition vs monoculture. A statistically significant increase in the content of total polyphenols and their antioxidant activity in velvetleaf plants indicates the difficulty of removing weeds from crops, especially resistant populations. The research conducted and the results obtained confirm that weeds in competitive conditions manifest their natural competitive advantage, which is further enhanced by crop feeding.

Utilization of yellow velvetleaf and water spinach to reduce copper ion in surface water of the estuary of babon river Semarang

The Babon River in East Semarang has been polluted by heavy metals sourced from industrial waste. So that water pollution at the Babon River estuary does not spread, it is necessary to carry out water treatment. This research uses a glass aquarium reactor and utilizes yellow velvetleaf (limmoncharis Flava) and water spinach (Ipomoea aquatic fork) plants as a medium to reduce the concentration of copper ions (Cu2+) by using variations in detention time. The results and analysis showed that yellow velvetleaf and water spinach could reduce the concentration of copper ions (Cu2+) in estuary surface water within 1 hour, 2 hours, 3 hours, and 5 hours. After going through several stages of a simple drinking water pre-treatment process, the results showed that yellow velvetleaf plants could reduce the concentration of copper ions (Cu2+) in Babon river water samples, from an initial concentration of 0.055 mg/L to 0.020 mg/L, with the highest efficiency percentage reduction up to 61.5%. As for water spinach, the concentration of copper ions that can be reduced only reaches the lowest level of 0.047 mg/L, with the highest percentage reduction efficiency of only 9.6% after the same pre-treatment process.

The Ethnopharmacology, Phytochemistry, Pharmacology Activities of Yellow Velvetleaf Plant (Limnocharis flava): A Review

Ethnopharmacology is a scientific study that connects a group of people, health, and the habits of the people who use traditional medicines and formulating traditional medication. The yellow velvetleaf plant is a type of plant that lives in water. This plant can be used as a vegetable for daily consumption by the community. The yellow velvetleaf plant is a plant of the Alismataceae family. This plant is ethnopharmacological, in which there is a pharmacological effect related to treatment and health maintenance for the community because it has chemical compounds such as saponins, steroids, phenol hydroquinone, and also mineral contents: Phosphorus (P), Calcium (Ca), Potassium (K), Sodium (Na), Iron (Fe), and Zinc (Zn). This review article discusses the chemical compounds in yellow velvetleaf plants and the pharmacological effects of yellow velvetleaf plants. In this review article, it is known that yellow velvetleaf plants, used by the community as a local vegetable, have chemical compounds that can produce pharmacological effects.

Plant Density and Rhizosphere Chemistry: Does Marigold Root Exudate Composition Respond to Intra- and Interspecific Competition?

The development of techniques to non-destructively monitor allelochemical dynamics in soil using polydimethylsiloxane (PDMS) microtubing (silicone tubing microextraction, or STME) provides a means to test important ecological hypotheses regarding the roles of these compounds in plant-plant interactions. The objective of this study was to investigate the impact of intra- and interspecific competition on the exudation of thiophenes by marigolds (Tagetes patula L.). Marigolds were grown at a density of 1, 3 and 5 plants in pots (8.75 × 8.75cm) containing two STME samplers. An additional treatment included one marigold surrounded by four velvetleaf (Abutilon theophrasti L.) plants. Marigold roots released two primary thiophenes, 3-buten-1-ynyl)-2,2'-bithienyl and α-terthienyl, which are readily absorbed by silicone microtubing. Thiophene exudation was monitored over the period 15-36days after planting, at 2-5day intervals. At the end of the study, root and soil samples were also analyzed for thiophene content. Thiophene production per plant increased over time, and thiophene release was strongly correlated with plant size. These results indicate that thiophene release in this study was passively controlled by resource availability. However, poor growth of velvetleaf plants competing with marigold suggests that thiophenes negatively influenced velvetleaf growth. This study, then, provides indirect evidence that thiophene exudation is insensitive to neighbor identity but differentially effective in inhibiting the growth of heterospecific neighbors.

Adaptability to varying water levels and responsiveness to NPK fertilizer in yellow velvetleaf plant (Limnocharis flava)

Adaptability to varying water levels and responsiveness to NPK fertilizer in yellow velvetleaf plant (Limnocharis flava)

Velvetleaf regenerates and reproduces after cropping

Velvetleaf (Abutilon theophrasti) was accidentally introduced into New Zealand in 2016 and intensive efforts are being implemented to mitigate the risk of its naturalisation. This study investigated the possibility of velvetleaf plants surviving in maize fields following silage harvest in late summer and early autumn. Velvetleaf plants were grown to maturity in a glasshouse during the summer of 2017—2018. They were left to seed and senesce naturally and, on 28 February 2018, five senesced plants were “harvested” at each height (0, 30, 50, 70 and 150 mm) with varying numbers of leaf nodes remaining (0, 0, 1, 2 and 3 pairs respectively). Velvetleaf was capable of regeneration 2—4 weeks after “harvest” from these leaf nodes. Forty percent regeneration occurred with 1 pair of nodes; 80% (2 pairs); and 100% (3 pairs). All regenerated plants subsequently produced mature seed pods with viable seed (95% germination) 6—10 weeks following “harvest”. Maize silage crops are normally cut ~100 mm above ground level. In this study, velvetleaf was able to regenerate and reproduce following simulated maize silage harvest at, below and above, normal cutting height. Growers are advised to continue management strategies for velvetleaf to prevent seed set following maize silage harvest and before sowing of the next crop or pasture.

Corn and Velvetleaf (Abutilon theophrasti) Growth and Transpiration Efficiency under Varying Water Supply

The supply of soil resources is critical for the establishment and long-term competitive success of a plant species. Although there is considerable research on the effects of water supply on crop growth and productivity, there is little published research on the comparative response of crops and weeds to limiting soil water supply. The objective of this research was to determine the growth and transpiration efficiency of corn and velvetleaf at three levels of water supply. One corn or velvetleaf plant was grown in a large pot lined with plastic bags. When seedlings reached 10 cm, bags were sealed around the base of the plant, so the only water loss was from transpiration. Daily transpiration was measured by weighing the pots at the same time each day. The experiment was conducted in the fall of 2007 and in the spring of 2008. Four replicates of each species–water treatment were harvested periodically to determine biomass accumulation and leaf area. The relationship between cumulative aboveground biomass and water transpired was described using a linear function in which the slope defined the transpiration efficiency (TE). Corn TE was greater than velvetleaf TE in all treatments during both trials. In the fall trial, corn TE was 6.3 g kg–1, 47% greater than that of velvetleaf TE. In the spring trial, TEs of both species were lower overall, and corn TE increased with declining water supply. Corn produced more biomass and leaf area than velvetleaf did at all water-supply levels. Velvetleaf partitioned more biomass to roots compared with shoots during early growth than corn did. The ability of corn to generate more leaf area and its investment in a greater proportion of biomass into root growth at all levels of water supply may enable it to more-effectively avoid velvetleaf interference under all levels of soil-water supply.

Testing Leaf Multispectral Reflectance Data as Input into Random Forest to Differentiate Velvetleaf from Soybean

Velvetleaf (Abutilon theophrasti Medic.) infestations negatively impact row crop production throughout the United States and Canada’s eastern provinces. To implement management strategies to control velvetleaf, managers need tools for differentiating it from crop plants. 5 Band, 7 Band, 8 Band, and 16 Band multispectral datasets simulating LANDSAT 3 plus a blue band, LANDSAT 8, WorldView 2, and WorldView 3 spectral bands, respectively were tested as input into the random forest algorithm for velvetleaf soybean [Glycine max L. (Merr.)] discrimination. During two separate greenhouse experiments in 2014, leaf reflectance measurements were obtained at the vegetative growth stage of velvetleaf plants and two soybean varieties. The reflectance measurements were collected with a plant contact probe attached to a hyperspectral spectroradiometer. Leaf hyperspectral reflectance measurements were convolved to the four multispectral datasets with computer software. Overall, user’s, and producer’s accuracies and kappa coefficient were employed to determine classification accuracies. Using the multispectral datasets as input, the random forest algorithm differentiated velvetleaf from the soybean varieties with accuracies ranging from 86.7% to 100%. 7 Band, 16 Band, 8 Band, and 5 Band datasets ranked or tied for the highest accuracies seventeen, sixteen, twelve, and one time, respectively. Kappa coefficients indicated an almost perfect agreement (i.e., kappa value, 0.81 - 1.0) to substantial agreement (i.e., kappa value, 0.61 - 0.80) between reference data and model predicted classes. This study was the first to demonstrate the application of the random forest machine learner and leaf multispectral reflectance data as tools to distinguish velvetleaf from soybean and to identify multispectral band combinations providing the best accuracies. Findings support further application of the random forest machine learner along with remotely-sensed multispectral data as tools for velvetleaf soybean discrimination with future implications for site-specific management of velvetleaf.

EVALUATION OF VELVETLEAF INTERFERENCE WITH MAIZE HYBRIDS AS INFLUENCED BY RELATIVE TIME OF EMERGENCE

SUMMARYThe presence of velvetleaf (Abutilon theophrasti) in crops is increasing in arid and semi-arid environments. Field experiments were conducted in Greece in 2009 and 2010 to determine the influence of velvetleaf emergence time and maize (Zea mays) hybrids with different growth rates on maize yield and velvetleaf growth and fecundity. Velvetleaf was uniformly seeded in order to emerge at the 1, 3, 5 and 7-leaf stage of maize (V1, V3, V5 and V7 growth stages, respectively). Velvetleaf biomass, canopy area and seed production were significantly affected by the date of velvetleaf emergence. Velvetleaf plants emerging just after maize (V1) produced 7–17 times lower seed number, compared with the V5 growth stage. Maximum maize grain yield loss ranged from 26 to 37% for early emerging velvetleaf, and less than 6% yield loss occurred from velvetleaf seedlings emerging at V7 growth stage. Maize hybrids with high initial growth rate seem to be more competitive than the other hybrids. The results of this study are essential in the development of an integrated weed management strategy for maize in semi-arid environments, since they highlight the importance of the careful selection of a competitive maize hybrid and avoidance of early velvetleaf emergence.

Biological Suppression of Velvetleaf (Abutilon theophrasti) in an Eastern Nebraska Soil

Weed-suppressive soils contain naturally occurring microorganisms that suppress a weed by inhibiting its growth, development, and reproductive potential. Increased knowledge of microbe–weed interactions in such soils could lead to the identification of management practices that create or enhance soil suppressiveness to weeds. Velvetleaf death and growth suppression was observed in a research field (fieldA) that was planted with high populations of velvetleaf, which may have developed via microbial mediated plant–soil feedback. Greenhouse studies were conducted with soil collected fromfieldA(soilA) to determine if it was biologically suppressive to velvetleaf. In one study, mortality of velvetleaf grown for 8 wk insoilAwas greatest (86%) and biomass was smallest (0.3 g plant−1) in comparison to soils collected from surrounding fields with similar structure and nutrient content, indicating that suppressiveness ofsoilAwas not likely caused by physical or chemical factors. WhensoilAwas autoclaved in another study, mortality of velvetleaf plants in the heat-treated soil was reduced to 4% compared to 55% for the untreated soil, thus suggesting that suppressiveness ofsoilAis biological in nature. A third set of experiments showed that suppressiveness to velvetleaf could be transferred to an autoclaved soil by amending the autoclaved soil with untreatedsoilA; this provided additional evidence for a biological basis for the effects ofsoilA.The suppressive condition in these greenhouse experiments was associated with high soil populations of fusaria.Fusarium lateritiumwas the most frequently isolated fungus from roots of diseased velvetleaf plants collected fromfieldA, and also was the most virulent when inoculated onto velvetleaf seedlings. Results of this research indicate that velvetleaf suppression can occur naturally in the field and thatF. lateritiumis an important cause of velvetleaf mortality infieldA.

Environmental Effects on Velvetleaf (Abutilon theophrasti) Epicuticular Wax Deposition and Herbicide Absorption

Controlled environment experiments showed that velvetleaf plants grown under drought stress or low temperature (LT) treatments had greater leaf epicuticular wax (ECW) deposition compared to plants grown in soil with moisture at field capacity (FC) or a high temperature (HT) regime. Light intensity did not affect ECW deposition; however, increasing light intensity decreased the leaf ECW ester content and increased the secondary alcohol content. Plants grown at an LT regime or under FC had leaf ECW with fewer hydrocarbons and more esters than those grown at an HT or drought stress regime. Velvetleaf absorption of acifluorfen increased as light intensity decreased for plants grown in adequate soil water content, while the opposite was true for drought-stressed plants. Velvetleaf absorption of acifluorfen was approximately 3 and 10 times greater, respectively, with the addition of 28% urea ammonium nitrate (UAN) in comparison to crop oil concentrate (COC) or no adjuvant, regardless of the environmental treatments. Plants absorbed more acifluorfen when subjected to the LT regime in comparison to the HT regime when UAN was the adjuvant, while the opposite was true when COC was the adjuvant. Velvetleaf absorption of acifluorfen was not affected by drought stress when COC or no adjuvant was used and varied between studies when UAN was used. Velvetleaf absorption of bentazon was greatest for plants grown under HT/FC or high light/FC treatments and least with plants grown under HT/drought stress or low light/drought stress treatments, regardless of the adjuvant. However, bentazon absorption was higher with the addition of an adjuvant and for plants grown at a high light intensity or FC condition compared with medium to low light intensity or drought stress treatments.

Competition of velvetleaf (Abutilon theophrasti M.) weed with cotton (Gossypium hirsutum L.). Economic damage threshold

The effect of the weed Abutilon theophrasti M. (common name: velvetleaf) on the growth of cotton grown in the Guadalquivir Valley, was studied by examining the influence of weed density on growth of the weed and that of cotton. Velvetleaf impeded normal cotton growth caused production losses as a result of the stress the cotton was subjected to. Additionally there was competition among velvet leaf plants at high velvet leaf densities. The influence of velvetleaf density in coexistence with cotton has been also studied evaluating weed effect on the biomass of cotton and its production. Additional determinations included the velvetleaf seed production capacity per unit area and seed production per plant. These determinations were adjusted to hyperbolic, inverse linear and logistic models. Last, the economic damage threshold (EDT) was calculated using the efficiency level in control of velvetleaf in cotton. In this calculation the treatment cost and losses caused by the weed, in the crop, were taken into account. The EDT varied between 0.1 and 0.5 velvetleaf plant m-2, depending on the control methods used.

First Report of Tobacco mosaic virus in Abutilon theophrasti in China.

Velvetleaf (Abutilon theophrasti Medic), a tall, fecund, self-fertile annual plant in the family Malvaceae, is widely grown in China as a fiber crop and for its medicinal properties. In July of 2008, we observed diffuse chlorotic and necrotic spots on the oldest leaves of velvetleaf plants in the field in Shanxi Province. Sap extracts from six symptomatic plants were tested by direct antigen coated ELISA using polyclonal antibodies specific to Potato virus Y (PVY) and monoclonal antibodies specific to Tomato mosaic virus (ToMV), Cucumber mosaic virus (CMV), and Tobacco mosaic virus (TMV). Five of the six samples were negative for ToMV, CMV, and PVY but positive for TMV. Double-stranded RNA extracted from leaves of the five velvetleaf plants was used as template for reverse transcription (RT)-PCR as described by Krajačića et al. (1) and Li et al. (2) with some modifications. One-step RT-PCR was performed using a Quant One Step RT-PCR Kit (TIANGEN BIOTECH CO., LTD., Beijing, China) with sense (5'-CTGTTTAGCCGGTTTGGT-3'), and antisense (5'-TCCCTTTACGGACATCAC-3') primers (3) designed to specifically amplify a fragment of the movement protein coding region of TMV. The expected 470-bp fragments were amplified from dsRNA from these five plants and the amplicon from each plant was cloned and sequenced (GenBank Accession No. FJ873800). Comparisons of a consensus sequence derived from the five amplicons with the nucleotide sequences available in the NCBI database using BLAST showed 99% identity with TMV from South Korea (GenBank Accession No. AB354955) and Spain (Accession No. AJ308692) and 98% with TMV from China (Accession No. AF165190). The serological, RT-PCR results and sequence data revealed that these velvetleaf plants were infected by TMV. On the basis of the serological analysis and genome sequence comparisons, this isolate was tentatively designated as TMV-Velvetleaf. To our knowledge, this is the first report of TMV in Abutilon theophrasti Medic in China.

Direct application end effector for a precise weed control robot

A direct chemical application end effector was developed to directly apply chemical via a weed's vascular tissue by cutting the weed's stem and wiping chemical on to its cut surface. The end effector consists of two micro-pumps, a custom-designed circular saw with a DC motor, an applicator, a chemical tank, a flow controller, and a micro reservoir. The field robot, equipped with a computer and a 5-degree of freedom arm, controls the movement of the direct chemical application end effector. A direct chemical application end effector was tested to quantify the application dose and to examine the potential for controlling weeds. The average application dose of the end effector ranged from 21.89 mg to 56.18 mg per target, with a coefficient of variation (CV) range of 33.79–60.85%. Using the direct chemical application end effector, chemical was applied to two species of weeds, yellow foxtail (Setaria glauca) plants and velvetleaf plants (Abutilon theophrasti) as representative grass and broadleaf weeds, respectively. The majority of the weeds (90.9%) treated by the end effector showed symptoms of chemical application on the sixth day and was dead ten days after application although the end effector used only 22% of active ingredient of a broadcast application. The developed end effector may provide a solution to reduce chemical use in field application, to increase herbicide efficacy, and to limit the herbicide contamination in the environment by directly applying a minute amount of herbicide only to weeds.

Velvetleaf (Abutilon theophrasti) Response to Glyphosate on the Field Edge

Control of weeds growing around field edges to limit seed production is an important component of preventative weed management. POST herbicide rates that are effective on weeds growing within a dense corn or soybean canopy may not be high enough to control weeds at the edge of a field. A study was conducted from 2004 through 2006 to compare velvetleaf growth and fecundity at the edge of the field as opposed to within the crop in response to a range of glyphosate rates. Treatments included position (plot center or edge), time of emergence (VE or V4 crop growth stage) and glyphosate rate (0 to 900 g ae ha−1). Without herbicide application, velvetleaf plants grown on the edge flowered earlier, had thicker stems, and produced more seed capsules than plants grown in the center of the plots. At glyphosate application rates of 200 to 900 g ha−1, the percentage of plants surviving and reproducing was higher on the edge than within the crop. Edge plants treated with 900 g ha−1of glyphosate produced more seeds than center plants that received no herbicide. Dose–response curves were used to estimate the glyphosate rate that would reduce seed production of surviving plants to 80% of the untreated plants. Plants emerging at the VE stage were estimated to require 300 g ha−1within the corn or soybean canopy and 668 g ha−1on the crop edge, whereas plants emerging at the V4 stage would require 0 g ha−1within the canopy and 280 g ha−1on the crop edge.

Heterologous Hybridization of Cotton Microarrays with Velvetleaf (Abutilon theophrasti) Reveals Physiological Responses Due to Corn Competition

Microarray analysis was used to identify changes in gene expression in velvetleaf that result from competition with corn. The plants were grown in field plots under adequate N (addition of 220 kg N ha−1) to minimize stress and sampled at the V6 growth stage of corn (late June). Leaf area, dry weight, and N and P concentration were similar in velvetleaf plants grown alone or with corn. Competition, however, did influence velvetleaf gene expression. Genes involved in carbon utilization, photosynthesis, red light signaling, and cell division were preferentially expressed when velvetleaf was grown in competition with corn. A less clear picture of the physiological impact of growth in monoculture was provided by the data. However, several genes involved in secondary metabolism and a gene preferentially expressed in response to phosphate availability were induced. No differences were observed in genes responsive to water stress or sequestering/transporting micronutrients.

Influence of relative time of emergence on nitrogen responses of corn and velvetleaf

Nitrogen (N) management markedly affects weed competition with crops. The effect of N availability on plant competition varies with a plant's abilities to capture and use N. Accordingly, we expected the N effect on plant competition to change with the relative emergence time of competing individuals. This hypothesis was tested by growing corn and velvetleaf plants in target and neighbor roles and comparing their N responses. Sowing times were varied, so that target plant emergent dates were constant, whereas neighbor plants were sown to emerge 7 d before, with, or 7 d after targets. Seedlings were fertilized daily with 2.5 mmol (“low N”) or 10.0 mmol (“high N”) ammonium nitrate (NH4NO3). Corn had greater total weight, leaf area, and root-to-shoot ratio (RSR) than velvetleaf. Different dry weights may have reflected seed weights; corn seed weight was greater than velvetleaf. Regardless of role, corn and velvetleaf dry weight and leaf area were greater with high N than low N; in contrast, RSR was lower with high N than low N. The RSR response to N availability suggested plant resources were shifted from N foraging, toward competition for photosynthetically active radiation (PAR). In target plants of each species, dry weight and leaf area increased linearly with time between target and neighbor emergence. Conversely, dry weight and leaf area of neighbor plants decreased with time between target and neighbor emergence. The N response of neighbor plants increased with time of emergence between target and neighbor emergence. Larger plants likely required more N to sustain growth than smaller plants; plants that emerged earlier likely had greater daily N requirements than those that emerged later. These results support factoring in emergence when predicting N effects on plant competition. Optimal N provisioning for integrated weed management may differ with emergence times of competing plants.

Fungal infection and soybean competition induce plastic responses in velvetleaf (Abutilon theophrasti) growth and reproductive output

The historic maternal environment; the identity of competing, neighboring plants; and biotic stresses, such as fungal disease and herbivory, interact to influence the competitive ability, reproductive output, and plasticity of weed populations. A weed capable of altering its phenotype in response to environmental factors is better able to compete for resources in agroecosystems, thereby reducing crop yields and contributing more seeds to the seed bank. Velvetleaf is a highly competitive annual weed in many North American cropping systems, exhibiting a high degree of phenotypic plasticity in response to biotic and abiotic factors. We examined the effects of seed size (small and large), competitive environment (with and without soybean), and stress level (none = no treatment, moderate = pathogen inoculation, high = pathogen plus herbicide) on velvetleaf allometry and reproductive output during three field seasons. Only under the high-stress treatment was velvetleaf biomass, height, and reproductive output compromised (&gt; 15% each), and these traits were further reduced with soybean competition. Soybean competition alone reduced velvetleaf biomass (&gt; 50%), height (25%), and seed output (50%), but effects of competition varied with stress level. Velvetleaf plants that originated from large seeds (≥ 10 mg) generally outperformed plants originating from small seeds (&lt; 10 mg) except under the high-stress treatment. These findings suggest that velvetleaf life-history traits and reproductive output in the current generation are a function of both present and historic factors. Management strategies for this species should involve tactics that not only reduce its competitive ability (e.g., biomass, height) but also decrease its seed production via synergistic stressors such as increased crop competitiveness, reduced-rate herbicide applications, and pathogen infection.