Browsing by Subject "Biologischer Pflanzenschutz"

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    Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops
    (2017) Weinmann, Markus; Neumann, Günter
    Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of “bio-effectors”, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of “bio-effectors” is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.
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    Publication
    Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops.- 2nd unrevised edition
    (2019) Weinmann, Markus; Madora GmbH, Luckestr.1, D-79539 Lörrach; Raupp, Manfred G.
    Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of “bio-effectors”, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of “bio-effectors” is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.
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    Strategien zur Regulierung des Fruchtschalenwicklers Adoxophyes orana F.v.R. (Lepidoptera: Tortricidae) mit Kombinationen des Neem-Präparates NeemAzal-T/S und Entomopathogenen
    (2002) Kumpmann, Sophia Katharina; Zebitz, Claus P. W.
    The summer fruit tortrix moth Adoxophyes orana F.v.R. is known as a serious pest in pome fruits in Central Europe. According the new laws on plant protection in Germany, only few registered products are left which may be used in organic and conventional farming at present. The registered products used in organic farming base on the specific Adoxophyes orana granulovirus (AoGV; tradename: Capex) and Bacillus thuringiensis (Bt). The application of Capex in order to reduce high population densities led to various results, some of which proved to be insufficient. The results of Bt application were not satisfying, either. The application of 3 l/ha NeemAzal-T/S, a product based on Neem (Azadirachta indica A. Juss.) -extracts and plant oil, for aphid control in apple orchards shows promising side effects on Adoxophyes orana with a mortality rate of about 60 - 70%. However, the efficacy of the recommended dose of 3 l/ha at red bud stage is not high enough to obtain a satisfying control of A. orana in orchards with medium and high population densities. A possible positive aspect may be the long-term effect upon the population of A. orana following the application of both, Capex or NeemAzal-T/S. Until now, however, long-term effects have not been considered in control strategies. Thus, this study aimed towards to take advantage of these side effects of the application of NeemAzal-T/S in combination strategies with Bacillus thuringiensis or Capex for efficient and economically interesting control of this pest. Field and laboratory tests were carried out to test different strategies of combinations including short-term and long-term effects of the products. In addition, the aim of some laboratory trials was to test appropriate Bt-products and further additives for A. orana regulation. Combination of NeemAzal-T/S and a Bt-product In laboratory trials and field tests, different concentrations of NeemAzal-T/S and Bt were combined and sprayed at the same time to assess the effects of this strategy on the larvae of A. orana. This combination showed neither additive nor synergistic effects, no matter the concentration used. A successive strategy with a first application of NeemAzal-T/S either with or without adding 0,4 kg/ha Bt and with a second application of 0.6 ? 1.0 kg/ha Bt lead to high efficacy. Application of NeemAzal-T/S ? in doses of 2 l/ha or 3 l/ha in the first treatment ? turned out to be an important factor to achieve a good result. The addition of 0.4 kg/ha Bt to the first application did neither show a better nor a worse result. Obviously, this successive combination strategy leads to lower negative influence of the feeding inhibition, which seems to be partly responsible for the negative effects on A. orana when both products were applied at the same time. Combination of NeemAzal-T/S and Capex In organic farming, Capex at 100 ml/ha is applied two times in spring. Aim of the following tests was to minimise the risk of failure of a treatment with Capex by taking advantage of the positive side effects of the application of NeemAzal-T/S and to find out whether a reduction of the amount of Capex may be possible in this combination. In laboratory trials, no synergistic effects of a combined application of both products could be observed. In fields, Capex applications leading to 50 ? 60 % efficiency could be raised to 81 ? 94% by adding of NeemAzal-T/S. When Capex applications led to a larval mortality rate of 90% or more, the addition of NeemAzal-T/S showed no effects. Furthermore, the long-term effects of the combination of NeemAzal-T/S and Capex were taken into account. One trial showed that the increased efficiency of the combination was higher when considering also the number of larvae of the subsequent two generations, than assessing the larval mortality rate in the treated generation only. This leads to the conclusion that either the long-term effect of NeemAzal-T/S alone or of both products together reduces the population density of A. orana in the generations following the treatment. Long-term effects of Capex Aim of this part of the studies was to estimate whether an application of a small amount of Capex in summer in addition to the usual spraying in spring leads to a higher infection potential in the orchard. With the additional treatment, the rate of infected larvae in summer could be increased from 8% to 22%, and the amout of damaged fruits from 0.2 % to 0.6%. But both infestation rates were very low and, thus, too weak to support any interpretation. Thus, the additional treatment in the summer turned out to be of economical advantage. The repeated use of this virus product in various concentrations and against various generations of A. orana seems to be a very promising strategy. It remains to further research and long-term studies to elucidate the most efficient sequence, amount and dates of application of the virus to obtain maximum control of A. orana.