Cultivation of cover crops is a valuable practice in sustainable agriculture. In cover crop management, the method of desiccation is an important consideration, and one widely used method for this is the application of glyphosate. With use of glyphosate likely to be banned soon in Europe, the purpose of this study was to evaluate the herbicidal effect of pelargonic acid (PA) as a bio-based substitute for glyphosate. This study presents the results of a two-year field experiment (2019 and 2021) conducted in northeast Germany. The experimental setup included an untreated control, three different dosages (16, 8, and 5 L/ha) of PA, and the active ingredients glyphosate and pyraflufen. A completely randomised block design was established. The effect of the herbicide treatments was assessed by a visual estimate of the percentage of crop vitality and a comparison assessment provided by an Ebee+ drone. Four vegetation indices (VIs) calculated from the drone images were used to verify the credibility of colour (RGB)-based and near-infrared (NIR)-based vegetation indices. The results of both types of assessment indicated that pelargonic acid was reasonably effective in controlling cover crops within a week of application. In both experimental years, the PA (16 L/ha) and PA_2T (double application of 8 L/ha) treatments demonstrated their highest herbicidal effect for up to seven days after application. PA (16 L/ha) vitality loss decreased over time, while PA_2T (double application of 8 L/ha) continued to exhibit an almost constant effect for longer due to the second application one week later. The PA dosage of 5 L/ha, pyraflufen, and a mixture of the two exhibited a smaller vitality loss than the other treatments. However, except for glyphosate, the herbicidal effect of all the other treatments decreased over time. At the end of the experiment, the glyphosate treatment (3 L/ha) demonstrated the lowest estimated vitality. The results of the drone assessments indicated that vegetation indices (VIs) can provide detailed information regarding crop vitality following herbicide application and that RGB-based indices, such as EXG, have the potential to be applied efficiently and cost-effectively utilising drone imagery. The results of this study demonstrate that pelargonic acid has considerable potential for use as an additional tool in integrated crop management.

Summary The effects of temperature and absence of a host plant on the population dynamics of the sheath nematode, Hemicycliophora conida, were studied under glasshouse conditions. Regarding temperature, population dynamics of H. conida on tomato ‘Moneymaker’ were monitored weekly over a period of 12 weeks. In the first experiment, with an average temperature of 21.4°C, population growth of H. conida continuously increased over time from an initial density of 106 nematodes (100 ml soil)−1 to a final density of 820 nematodes (100 ml soil)−1, resulting in a reproduction rate of 7.7. The time required to complete one generation was 6.5 weeks or 598 temperature degree days at 8°C base temperature (TDD8). A second experiment showed that the development of H. conida on tomato was faster at 22.1°C than at 19.0°C. At 22.1°C, one generation was completed after 6 weeks (= 588 TDD8) compared to 8 weeks (=634 TDD8) at 19.0°C. The higher temperature also resulted in a higher reproduction rate (93 at 22.1°C vs 7.8 at 19.0°C). In the absence of a host plant, the population density of H. conida decreased over time. However, this natural decline was less pronounced than for the root-knot nematode Meloidogyne hapla. In the first experiment, the population density of H. conida decreased within 18 weeks by 89.5%, while M. hapla was already no longer detectable 12 weeks after inoculation. In the second experiment, H. conida decreased by 98.2% within 16 weeks compared to 99.98% for M. hapla.