Response of Xanthium strumarium populations to sublethal applications of bentazone

Abstract

Summary: Résumé: Zusammenfassung Responses of 10 natural or agricultural populations of Xanthium strumarium to sublethal rates of bentazone applied post‐emergence were examined under field conditions. Both vegetative growth and reproduction of sprayed plants were affected by the herbicide. Some populations were more tolerant of bentazone than the others, but the degree of herbicide tolerance did not depend on the previous herbicide experience of a population. Bentazone treatment significantly reduced the weight per fruit in some populations, which in turn could affect the survival and growth of the subsequent seedlings. La réponse depopulations de Xanthium strumarium à des doses sublétales de bentazone Nous avons étudié au champ la réponse de dix populations naturelles ou agricoles de Xanthium strumariumà des doses sublétales de bentazone appliquée en post‐levée. L'herbicide affectait la croissance et la reproduction des plantes traitées. Quelques populations étaient plus tolérantes à la bentazone que d'autres, mais le degré de tolérance ne dépendait pas de l'exposition préalable des populations à l'herbicide. La bentazone réduisait significativement le poids des fruits dans quelques populations, ce qui pouvait affecter ensuite la survie et la croissance des jeunes plantes qui en étaient issues. Wirkung subletaler Dosen von Bentazon auf Xanthium strumarium Zehn Herkünfte von Xanthium strumarium wurden im Nachauflauf mit subletalen Dosen von Bentazon unter Feldbedingungen behandelt. Sowohl das vegetative Wachstum als auch die Samenbildung der behandelten Pflanzen wurden durch das Herbizid beeinträchtigt. Einige Herkünfte waren weniger empfindlich, doch der Grad der Herbizidempfindlichkeit stand nicht im Einklang mit früheren Erfahrungen über die Wirkung des Herbizids. Durch die Bentazon‐Be‐handlungen nahm das Gewicht der Samen bei einigen Herkünften signifikant ab, so daß ihre Lebensfähigkeit und das Wachstum der Keimpflanzen beeinträchtigt sein könnten.

Control of common cocklebur (Xanthium strumarium L.) in corn

“…Lack of effective control with bentazon plus atrazine in our study is in contrast with other studies that have shown significant reduction in growth and survival of common cocklebur with bentazon (Zhang et al 1994).…”

Effect of herbicide application on fruit characters of Xanthium strumarium L. populations

“…In X. strumarium, larger fruits are less susceptible to seed predation than smaller fruits owing to longer spikes or thicker fruit coats (Hare, 1980). The variations in fruit weight observed in our earlier study (Zhang et al, 1994) might have resulted from changes in seed mass, seed abortion rate and/or fruit coat thickness; the latter would alter the chance of seed predation and consequently seedling establishment.…”

“…In a previous study (Zhang et al, 1994) we observed that bentazone application reduced the fitness of X. strumarium by causing a substantial reduction in total weight and/or number of fruits. The mean weight of 100 fruits, however, showed slight variations in some populations but none at all in the others.…”

“…Two plots from each of the four blocks were randomly chosen for each population. The rest of the plots were assigned to other X. strumarium populations used for other purposes (Zhang et al, 1994). Within each plot, 30 fruits from a population were sown at 4-cm depth with 1 m space between any two adjacent fruits.…”

“…These were not direct effects of the herbicide as flower formation was not apparent until several weeks after spraying. However, many leaves were damaged and the overall rate of plant development was reduced by herbicide treatment (Zhang et al, 1994). Such damage may substantially reduce the amount of meristematic tissue and/or storage materials for fruit development.…”