Institut für Bienenschutz
The abundance of arable weeds in conventional and organic farming is controlled and minimized with chemical and mechanical methods. At the same time, flowering arable weeds are a potentially important food source for pollinating insects especially in periods when other food sources are scarce ("Trachtlücke"). We know relatively little about arable weed-pollinator interactions in relation to the plant or flowering density of arable weeds. For the majority of arable weed species, plant traits important for pollinators, such as nectar and pollen production, average flower number and flowering phenology, have not yet been adequately studied. These parameters can vary greatly depending on management (fertilizer application, tillage) and location (soil type, shading). This pilot study will further experiments on weed density as a function of spot spraying (BetterWeeds project) and monitor both arable weeds and bee flower visitors in a field study and a 'common garden' experiment in replicated plot observations. For this purpose, 10 replicated 1m x 1m quadrats with different arable weed compositions and densities will be repeatedly observed in two wheat fields at the time of weed flowering. Flower-visiting bees will be recorded and pollen loads of the visitors will be examined for their pollen composition. In the ‘common garden’ experiment, five of the most common weed species of the field study will be planted in replicated 1m x 1m quadrats. For each species, we will plant and monitor three qudrats with and three quadrats without accompanying wheat. At the same time of flower observations, arable weed traits (e.g. plant density, flowering duration) of the five species will be recorded and flower densities estimated. In addition, pollen and nectar production of different arable weed species will be quantified. The results will be used to estimate pollinator activity and attractiveness and serve as the basis for a larger replicated study. The generated data set will be used to initially estimate visitation frequency of pollinating bees and help farmers in their decision whether or not to use control measures of integrated pest management for certain arable weeds at certain times depending on the positive aspects of these weeds in bee enhancement.
Federal Ministry of Agriculture, Food and Regional Identity
