ALBERT

Notes: Metabolism of 14C asulam applied with surfactant was studied in Senecio Jacobaea L. and Medicago saliva L. Plants were harvested 48, 96 and 144 h after treatment and extracted with acetone. The aqueous residue of the acetone extract was partitioned with ethyl acetate and the 14C activity in the ethyl-acetate phase, the aqueous phase and the plant residue was determined. A significant amount of 14C activity was not extracted by acetone from either species. This amount increased with time in M. sativa but remained relatively constant in S. jacobaea. More 14C activity was found in the aqueous phase than in the ethyl-acetate phase in M. sativa while the reverse was true in S. jacobaea. Significantly lower amounts of free asulam were identified in M. sativa than in S. jacnbaea. Still, results of these and previous studies on retention, uptake and translocation do not completely account for differences in sensitivity found in greenhouse and field applications. Other possible explanations for selectivity are discussed.

Notes: Research conducted in El Salvador, Central America, demonstrated that an interval of 3 days between application of glyphosate and tillage was sufficient to cause 90% reduction in purple nutsedge (Cyperus rotundus L.) plants, while delays of 11–23 days generally gave slightly less reduction. à second application to the same plots 35 days following tillage resulted in more than 90% reduction with all intervals. Approximately 3 months after the initial treatment, tuber numbers had been reduced to half the original population. Germination of the remaining tubers was reduced by more than 50%.Glyphosate applied during the dry season caused an average of 79% reduction in plant numbers compared with 88% in the rainy season. However, in the dry season, the remaining plants had no competition from other weeds and after 5 months there was only à 40% reduction in nutsedge population. During the rainy season, 1, 2 and 3 kg/ha were equally effective, but 1 kg/ha was not sufficient in the dry season.

Notes: Senecio jacobaea L. and Medicago sativa L. plants grown in a glasshouse were treated with foliar applications of aqueous solutions of asulam. Retention on foliage, uptake and translocation were measured in both species. Retention was greater in S. jacobaea than in M. sativa when no surfactant was added and similar when surfactant was added. Addition of surfactant modified spray distribution and increased asulam uptake in M. saliva but did not in S. jacobaea. S. jacobaea translocated over twice as much asulam from the treated area as M. sativa. These data suggest that surfactant should not be added for maximum selectivity. Differences in species response to asulam treatments are partially, but not entirely, explained by differences in retention, uptake and translocation.

Notes: Naptalam applied to yellow nutsedge (Cyperus esculentus L., var leptostachvus Boeck.) plants through nutrient culture, as a foliar spray or to the soil surface significantly stimulated the transformation of rhizomes into new shoots when the plants were grown under a 20-h photoperiod. Applications of naptalam to plants grown under short-day conditions inhibited tuber production. Applications of glyphosate to yellow nutsedge foliage at 0·3 and 0·6 kg ha resulted in 57 and 68% dormant tubers respectively, compared to 27% in untreated plants. These lower rates did not significantly increase the number of nonviable tubers. The application of 1·1 and 2·2 kg ha resulted in 47 and 52% dormant tubers, respectively and approximately 40% nonviable tubers. When production of new shoots of yellow nutsedge was induced by soil treatment with napialam and followed later with glyphosate significantly greater control of the nutsedge was observed than from either herbieide alone.Effets du naptalame sur la crossance du experus aune et efficaeite ulterieure du glyphosate.Le naptalame appliquè sur des plantes de cypérus jaune (Cyperus esculentus L. var leptostachyus Boeck) a vee des éléments nutritifs, en pulvérisation fobaire ou à la surface du sol a significativement stimulé la transformation des rhizomes en nouvelles pousses forsque les plantes ont été soumises à une photopériode de 20 h. Les applications de naptalame aux plantes pousant dans des conditions de jours courts ont inhibe la production des tubercules. Des applications de glyphosate sur le feuillage du cypérus jaune à 0.3 et 0.6 kg ha ont donné respectivement 57 et 68% de tubercules dormants contre 27% chez les plantes non traitées. Ces doses plus faibles n'ont pas augmente significativement le nombre de tubercules nonviables. L'application de 1.1 et 2.2 kg ha a donné respectivement 47 et 52% de tubercules dormants, et approxativement 40% de tubercules non viables. Lorsque la production de nouvelles pousses de cypérus jaune a été induite par un traitement du sol au naptalame. suivi ulterieurement d'une application de glyphosate. l'efficacite observée sur le cypérus a été significativement meilleure qu'avee l'un ou l'autre de ces herdicides employé soul. Der Einfluss von Naptalam auf das Wachstum von Cyperus esculentus L. und nachfolgender Bekämpfung mit GlyphaxateWird Naptalam in die Nähelösungskultur oder auf das Blatt von Cyperus esculentus var leptostachyus Boeek, sowj́e auf die Bodenoberfläche appliziert so stimulieri es die Bildung von neuen Trieben aus Rhizomen, wenn die Pflazen einer Photoperiode von 20 Std. ausgesetzt werden. Unter Kurztagshedingungen hemmt Napralam die Bildung von Knollen Wurde Naptalam auf die Blätter mít 0.3 und 0.6 kg ha appliziert so stieg die Zahl der dormanten Knollen von 27% bei unbehandelt auf 57% und 68% bei behandelt. Diese niedrigen Aufwandmengen steigerten die Zahl der keimfähigen Knollen nicht significant. Die Applikation von 1.1 und 2.2 kg ha resultiere in 47 und 52% dormanten und 40% nicht keimfähigen Knotlen. Wenn die Bildung von Trieben durch eine Behandlung mit Naptalam über dem Boden induziert wurde und diese nachfolgend mit Bekämpfungserfolg als wenn jades Herbizid allein angewandt wurde.

Notes: Summary. Significant stimulation of root or shoot growth of oats (Avena sativa L.) resulted from pre-emergence applications of eleven herbicides at sublethal doses. Two additional herbicides stimulated cucumber (Cucumis sativus L.) root growth. Several types of herbicides with different mechanisms of lethal action were represented. Three herbicides failed to stimulate plant growth significantly in these studies, although all of them have been observed to cause growth stimulation in other experiments. Studies on oat seedling respiration, photosynthesis, protein content, free amino acid content, and total available soluble carbohydrates failed to provide any consistent explanation for stimulation. These results provide further evidence of the validity of the Arndt-Schulz hypothesis which states that all poisons are stimulatory at sublethal concentrations.Stimulation de la croissance des plantes par des concentrations sublétales d'herbiddesRésumé. Une stimulation significative de la croissance des racines ou des tiges de I'avoine (Avena sativa L.) a été provoquée par l'application en pré-levée de onze herbicides à des doses sublétaies. Deux autres herbicides ont stimulé la croissance des racines de concombre. Plusieurs types d'herbicides possédant des mécanismes diffrénts d'action létale étaient représentés. Trois herbicides n'ont pas provoqué de stimulation significative de la croissance au cours de cette étude, bien qu'ils aient provoqué une stimulation dans d'autres expériences. Des recherches sur la respiration, la photosynthése, la teneur en protéines, en amino-acides libres et le total disponible des hydrates de carbone solubles dans la plantule d'avoine n'ont fourni aucune explication logique de la stimulation. Ces résultats apportent une nouvelle preuve de la validité de l'hypothése d'Arndt-Schulz selon laquelle tous les poisons ont un effet stimulant à des concentrations sublétaies.Förderung des Pflanzenwachstums durch Herbizide in sublethalen KonzentrationenZusammenfassung. Die Vorauflaufanwendung von elf Herbiziden in sublethalen Dosen förderte das Wurzel- und Sprosswachstum von Hafer (Avena sativa L.) signifikant. Zwei weitere Herbizide stimulierten das Wurzelwachstum bei der Gurke (Cucumis sativus L.). Es waren Herbizide aus verschiedenen Gruppen mit unterschiedlichem Mechanismus der lethalen Wirkung vertreten. Drei Herbizide förderten in diesen Studien das Wachstum nicht signifikant, obwohl eine solche fördernde Wirkung in anderen Experimenten beobachtet worden war. Untersuchungen der Atmung von Haferkeimlingen, der Photosynthese, des Proteingehaltes, des Gehaltes an freien Aminosäuren und der Gesamtmenge an löslichen Kohlenhydraten erbrachten keine einheitliche Erklärung für die Förderung. Diese Ergebnisse stützen die Gültigkeit der Arndt-Schulz Hypothese, die besagt, dass alle Gifte in sublethalen Dosen stimulierend wirken.