Browsing by Subject "Morning glory"

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Generative sowie vegetative Vermehrung, Entwicklung, Morphologie und chemische Bekämpfung der windenden Unkrautarten: Calystegia sepium (L.) R. Br., Convolvulus arvensis L., Ipomoea hederacea Jacq., Ipomoea purpurea (L.) Roth und Fallopia convolvulus L.
(2013) Willeke, Leonie; Gerhards, Roland
Vining weed species as the two perennial plants Calystegia sepium and Convolvulus arvensis, and the annual species Ipomoea hederacea, Ipomoea purpurea and Fallopia convolvulus are very important in agriculture worldwide due to their high competitive ability. The aim of this work is to gain a better understanding of the morphology, physiology and reproduction of these species and the efficacy of herbicides on the weeds to develop improved control strategies with this knowledge. The first section of this paper consists of studies about the generative propagation and seed germination in response to various factors. It is shown that the species of the family of Convolvulaceae have morphological similarities and any weed species can germinate in a wide temperature range and in all studied soil types. The proliferation studies revealed that the rhizome and root pieces of Calystegia sepium and Convolvulus arvensis are dormant in the winter and sprout in spring. In addition, several buds on rhizome and root pieces also directly next to each other can sprout and the percentage of sprouting increases with the number of buds. Additionally, a negative linear relationship between the burial depth of the rhizome and root pieces in the soil and the ability to emerge is determined. In addition to these results, the analysis of the starch and sugar concentrations during a growth period shows that the starch concentration reaches its minimum 1.5 months before flowering. In the second part of this work, the main focus is placed on weed control with herbicides especially with the novel active substance TCM (Thiencarbazone-methyl), an acetolactate synthase (ALS) inhibitor, whose mechanism is investigated. The active ingredient TCM remains stable in the vining weeds and does not degrade as in corn. Proven TCM is absorbed through the leaves and transported systemically. TCM causes a disruption of the amino acid balance. The increase of the branched amino acids is carried out in dependence of the time as well as the applied herbicide concentration. TCM under greenhouse conditions as well as the active ingredients dicamba, glufosinate and glyphosate, frequently used in corn, control annual and perennial weed species germinated from seeds to a degree of more than 85% in the full and half field application rate. In comparison, the efficacy of shoot control of vegetatively propagated perennial plants is about 5-15% lower. Nevertheless, the regrowth of rhizome and root pieces is suppressed by the herbicide applications almost completely. The studies of the control in different growth stages show that the effect of TCM, dicamba and glyphosate on the annual species is greater in earlier stages of growth; however, the generatively propagated plants are controlled constantly even high in the later stages of growth. In contrast, with an increasing shoot length from 5 cm to 30 cm, the efficacy of control of the vegetatively propagated plants decreases to an average 40 %. The obtained control of Calystegia sepium and Convolvulus arvensis after a spring and a fall application under field conditions is much lower than under greenhouse conditions. Post-emergence application at recommended field application rates results in a reduction in the aboveground biomass of Calystegia sepium with TCM about 65% and of Convolvulus arvensis to a maximum of 50% with TCM, TCM in combination with TBT(tembotrione) and dicamba. The herbicides dont reduce the sprouting ability of underground organs of both species; and corn yield isnt even increased by the use of a herbicide against Convolvulus arvensis. Fallopia convolvulus, an annual species, is controlled in field trials by TCM and TCM in combination with TBT in the normal field application rate to an extent of more than 90 %, also with dicamba. The control results of Ipomoea hederacea in the two experimental years vary greatly. On average, the efficacy of the application of TCM in combination with IFT (isoxaflutole), glufosinate and dicamba in combination with diflufenzopyr is as high as in the greenhouse experiments with a rate of 95 %. In summary, the results show that young plants germinated from seeds in early growth stages can be controlled quite well above and below ground with the studied herbicides, so that TCM can be used to control Fallopia convolvulus as an alternative to other herbicides used conventionally. Despite the proven systemic translocation and inhibition of regrowth of rhizome and root pieces of vegetatively propagated perennial species TCM as well as the other tested herbicides do not provide suffcient long-term success of control of Calystegia sepium and Convolvulus arvensis in spring and in fall application under field conditions. The mechanical control of perennial species can be optimized by a strong division of the rhizome and root pieces in combination with a high burial depth.