ISHS Acta Horticulturae 73: I International Symposium on Spices and Medicinal plants
WEED CONTROL IN MEDICINAL PLANTS |
| Author: | G. Maas |
| Abstract:
For weed control in medicinal plants, the question is often asked whether the application of herbicides can be put into practise. As in literature information on weed control in these special crops is found very scarcely, great a number of experiments of our institute have studied this problem for many years. The experience gained is compiled in the tables no. 1 to 4, which show the practicability of application of 26 herbicides to 33 species of medicinal plants. Besides the possibility of using these herbicides there is a general know-how of applying pre-sowing compounds, which must be mentioned in the very beginning. In order to prevent a direct contamination of plants by herbicides, pre-sowing compounds should be favoured. Unfortunately the pre-sowing fumigation of the upper 5 cm of the soil with dazomet, 15 g/m2 a.i., is quite an expensive treatment. Diallate applied about 10 days before sowing or planting is successful on fields with grass weeds. Dipyridils, too, have a good effect in controlling weeds, especially at high infestation. When using the different herbicides listed in the tables, the optimal dosage is difficult to determine, as their effect both on medicinal plants as well as weeds is influenced by the sorption and the movement in the soil and by the absorption by the plants and by their catabolism. Therefore the exact dosages must be found for the individual habitats to achieve the effect desired in practise. When herbicides are used for weed control, it must always be considered that all plants, weeds as well as crops, absorbe the compound in different amounts. Herbicides may thus affect the metabolic processes in the crop - positively or negatively. Such effect may be visible or not. Several secondary effects on the crop can be: changing in colour, growth retardation, and changing of the contents of nitrogen, nitrates, carbohydrates, and last but not least the biochemical quality. Generally, such secondary effects do not last very long and have hardly an influence on the product. Up till now we found twice the content of azulene only in Matricaria chamomilla L., after it had been treated with linuron. The intensity of the herbicide effect on the metabolic processes in the crop is determined not only by the | |
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