The biology of Canadian weeds. 115. Conyza canadensis

Abstract

Weaver, S. E. 2001. The biology of Canadian weeds. 115. Conyza canadensis Can. J. Plant Sci. 81: 867-875. Conyza canadensis (L.) Cronq. (Canada fleabane, horseweed, mare's-tail) is a winter or summer annual, native to North America, and found in all provinces of Canada except Newfoundland. It is a weed of orchards, vineyards, roadsides, and arable fields where tillage has been reduced or eliminated. Most seedlings emerge from late August through October and form rosettes which overwinter. Large numbers of small, wind-dispersed seeds, ranging to over 200 000 seeds per plant, are produced in late summer. Populations of C. canadensis in more than ten countries have evolved resistance to herbicides such as paraquat, atrazine, chlorsulfuron or glyphosate. Several paraquat resistant populations were found in orchards in Essex Country, Ontario. It serves as a wild host of the tarnished plant bug, and of aster yellows, a mycoplasma disease transmitted by the aster leaf hopper. On la trouve dans toutes les provinces du Canada sauf Terre-Neuve. Elle envahit les vergers, les vignobles, les bords de route et les terres arables dont on ne travaille plus le sol, ou très peu. La plupart des plantules apparaissent de la fin du mois d'août à octobre et forment des rosettes qui hiverneront. La plante produit au-delà de 200 000 petites graines qui seront dispersées par le vent à la fin de l'été. Dans plus de dix pays, les peuplements de C. canadensis ont acquis une résistance à divers désherbants tels le paraquat, l'atrazine, le chlorsulfuron et le glyphosate. Plusieurs peuplements résistants au paraquat ont été découverts dans des vergers du comté d'Essex, en Ontario. La vergerette du Canada est l'hôte sauvage de la punaise grise et de la jaunisse de l'aster, mycoplasme transmis par la cicadelle de l'aster. Description and Account of Variation(a) Winter or summer annual, reproducing only by seeds; short taproot with laterals; seedlings form a basal rosette of dark green, sparsely hairy leaves, rarely more than 1 cm wide, with distinct petioles and coarsely toothed margins; the basal rosette deteriorates after the stem begins to elongate; stems are erect, 10-180 cm high, hairy, with many small flowering branches in the upper portions; stem leaves alternate, numerous and crowded on the stem, often appearing opposite or even whorled, lanceolate to linear, with nearly entire margins; upper stem leaves only 5 mm wide; flower heads (capitula) small, 3-5 mm in diameter, and numerous on short branches near the top of the main stem; pistillate ray florets are white, ligulate and very short, often concealed by involucre bracts around each head; perfect disk florets are yellowish-green and very fluffy at maturity; seeds (achenes), averaging 60-70 per capitulum, are small, 1-2 mm long, transparent and have an attached pappus 3-5 mm in length (Frankton and Mulligan 1987;Alex 1992).Conyza canadensis is a diploid species, with a chromosome number of 2n = 18 for Canadian and other specimens (Mulligan 1957; Federov 1969;Thebaud and Abbott 1995)....

Manejo de Conyza bonariensis resistente ao herbicida glyphosate

“…bonariensis é uma espécie nativa da América do Sul e ocorre na Argentina, Uruguai, Paraguai e Brasil. É uma planta anual que se reproduz por sementes que germinam no outono/inverno, com encerramento do ciclo na primavera e verão (Weaver, 2001). A espécie apresenta grande produção de sementes e fácil dispersão, caracterizando-se como agressiva (Kissmann & Groth, 1999).…”

Resistência de Conyza canadensis e C. bonariensis ao herbicida glyphosate

“…canadensis e C. bonarien sis (buv as) são espécies originárias dos Estados Unidos (Weaver et al, 2001), pertencentes à família Asteraceae, que possuem ciclo de desenvolvimento anual. São espécies extremamente prolí-ficas, podendo produzir até 200.000 sementes viáveis por planta, estabelecendo-se em diversas condições climáticas.…”

A weremit kiűzése a hasból. Óegyiptomi recept hatásosságának értelmezése az újabb kutatási eredmények alapján

“…A recept különös jelentőségét az adja, hogy a leírásban ajánlott Conyza ssp. egyike azoknak az Asteraceae családba tartozó Conyza spp.-nek, amelyek Európa-szerte is megtalálha-tók, és népgyógyászati jelentőségük is ismert [36,37].…”