Institut für Phytomedizin

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/14

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Assessing the capability of YOLO- and transformer-based object detectors for real-time weed detection
(2025) Allmendinger, Alicia; Saltık, Ahmet Oğuz; Peteinatos, Gerassimos G.; Stein, Anthony; Gerhards, Roland
Assessing the capability of YOLO- and transformer-based object detectors for real-time weed detection
(2025) Allmendinger, Alicia; Saltık, Ahmet Oğuz; Peteinatos, Gerassimos G.; Stein, Anthony; Gerhards, Roland
Spot spraying represents an efficient and sustainable method for reducing herbicide use in agriculture. Reliable differentiation between crops and weeds, including species-level classification, is essential for real-time application. This study compares state-of-the-art object detection models-YOLOv8, YOLOv9, YOLOv10, and RT-DETR-using 5611 images from 16 plant species. Two datasets were created, dataset 1 with training all 16 species individually and dataset 2 with grouping weeds into monocotyledonous weeds, dicotyledonous weeds, and three chosen crops. Results indicate that all models perform similarly, but YOLOv9s and YOLOv9e, exhibit strong recall (66.58 % and 72.36 %) and mAP50 (73.52 % and 79.86 %), and mAP50-95 (43.82 % and 47.00 %) in dataset 2. RT-DETR-l, excels in precision reaching 82.44 % (dataset 1) and 81.46 % (dataset 2) making it ideal for minimizing false positives. In dataset 2, YOLOv9c attains a precision of 84.76% for dicots and 78.22% recall for Zea mays L.. Inference times highlight smaller YOLO models (YOLOv8n, YOLOv9t, and YOLOv10n) as the fastest, reaching 7.64 ms (dataset 1) on an NVIDIA GeForce RTX 4090 GPU, with CPU inference times increasing significantly. These findings emphasize the trade-off between model size, accuracy, and hardware suitability for real-time agricultural applications.
Efficacy of various mechanical weeding methods - single and in combination - in terms of different field conditions and weed densities
(2021) Naruhn, Georg-Peter; Peteinatos, Gerassimos G.; Butz, Andreas F.; Möller, Kurt; Gerhards, Roland
Public awareness and environmental policies have increased interest in applying non-herbicide weed control methods in conventional farming systems. Even though mechanical weed control has been used for centuries in agricultural practice, continuous developments—both in terms of implements and automation technologies—are continuously improving the potential outcomes. Current mechanical weed control methods were evaluated for their weed control efficacy and effects on yield potential against their equivalent herbicide methods. Furthermore, not much is known about the correlation between weed control efficacy (WCE) of different mechanical methods at varying weed density levels. A total of six experiments in winter wheat (2), peas (2), and soybean (2) were carried out in the years 2018, 2019, and 2020 in southwestern Germany. Harrowing and hoeing treatments at different speeds were carried out and compared to the herbicide treatments and untreated control plots. Regarding the average WCE, the combination of harrowing and hoeing was both the strongest (82%) and the most stable (74–100%) mechanical treatment in the different weed density levels. Whereas, in average, hoeing (72%) and harrowing (71%) were on the same WCE level, but harrowing (49–82%) was more stable than hoeing (40–99%). The grain yields in winter wheat varied between 4.1 Mg∙ha−1 (control) and 6.3 Mg∙ha−1 (harrow), in pea between 2.8 Mg∙ha−1 (hoe slow) and 5.7 Mg∙ha−1 (hoe fast) and in soybean between 1.7 Mg∙ha−1 (control) and 4 Mg∙ha−1 (herbicide). However, there were no significant differences in most cases. The results have shown that it is not possible to pinpoint a specific type of treatment as the most appropriate method for this cultivation, across all of the different circumstances. Different field and weather conditions can heavily affect and impact the expected outcome, giving, each time, an advantage for a specific type of treatment.
Enhancing weed suppression in plants by artificial stress induction
(2025) Merkle, Michael; Petschenka, Georg; Belz, Regina; Gerhards, Roland
Various plant species from the Poaceae, Cannabaceae, and Brassicaceae families are used as cover crops to suppress weeds and volunteer crops through competition and allelopathy. This study examined the effects of artificially induced stress on the physiological processes, total phenolic content (TPC), and allelopathic potential of the plant species Avena strigosa, Cannabis sativa , and Sinapis alba at an early growth stage with the aim to increase their weed suppression abilities. Stress was induced at the 3–4 leaf stage in greenhouse-grown plants via harrowing, methyl jasmonate (MeJA) application, insect stress simulation, or a combination of insect stress and harrowing. Maximum quantum yield of photosystem II and shoot dry matter in the three plant species were only minimally or not affected a few days after treatment (DAT). Insect stress caused visible symptoms on treated leaves in all plants. The TPC in the shoot extracts of combined stress-treated C. sativa and insect-stressed S. alba was significantly higher by 1.7 and 1.9 times, respectively, five DAT compared to the shoot extracts from untreated control plants. Additionally, laboratory bioassays with aqueous shoot extracts from the untreated and treated plants were conducted to identify changes in allelopathic potential within the shoot tissues. The application of shoot extracts from MeJA-treated C. sativa and S. alba resulted in the lowest seed germination rates for the two weed species Alopecurus myosuroides and Stellaria media , as well as for the volunteer wheat Triticum aestivum , which were up to 65% lower 10 DAT compared to seeds treated with shoot extracts from non-stressed plants. However, the root-suppressing effect of the shoot extracts on weeds was not influenced by the stress treatments. This study reveals that artificial stress induction can be a suitable management strategy to enhance weed and volunteer cereal suppression in plants in an early growth stage but may vary between stress types and plant species, and requires further optimization and field testing.
Extracellular vesicles isolated from dsRNA-sprayed barley plants exhibit no growth inhibition or gene silencing in Fusarium graminearum
(2022) Schlemmer, Timo; Lischka, Richard; Wegner, Linus; Ehlers, Katrin; Biedenkopf, Dagmar; Koch, Aline
Numerous reports have shown that incorporating a double-stranded RNA (dsRNA)-expressing transgene into plants or applying dsRNA by spraying it onto their leaves successfully protects them against invading pathogens exploiting the mechanism of RNA interference (RNAi). How dsRNAs or siRNAs are transferred between donor host cells and recipient fungal cells is largely unknown. It is speculated that plant extracellular vesicles (EVs) function as RNA shuttles between plants and their pathogens. Recently, we found that EVs isolated from host-induced gene silencing (HIGS) or spray-induced gene silencing (SIGS) plants contained dsRNA-derived siRNAs. In this study, we evaluated whether isolated EVs from dsRNA-sprayed barley ( Hordeum vulgare ) plants affected the growth of the phytopathogenic ascomycete Fusarium graminearum . Encouraged by our previous finding that dropping barley-derived EVs on F. graminearum cultures caused fungal stress phenotypes, we conducted an in vitro growth experiment in microtiter plates where we co-cultivated F. graminearum with plant EVs isolated from dsRNA-sprayed barley leaves. We observed that co-cultivation of F. graminearum macroconidia with barley EVs did not affect fungal growth. Furthermore, plant EVs containing SIGS-derived siRNA appeared not to affect F. graminearum growth and showed no gene silencing activity on F. graminearum CYP51 genes. Based on our findings, we concluded that either the amount of SIGS-derived siRNA was insufficient to induce target gene silencing in F. graminearum, indicating that the role of EVs in SIGS is minor, or that F. graminearum uptake of plant EVs from liquid cultures was inefficient or impossible.
Impact of plastic rain shields and exclusion netting on pest dynamics and implications for pesticide use in apples
(2025) Bischoff, Robert; Piepho, Hans-Peter; Scheer, Christian; Petschenka, Georg
Apple production is among the most pesticide-intensive cultures. Recently, plastic rain shields and pest exclusion netting have emerged as potential measures to reduce the heavy reliance on chemical pesticides in apple, due to their inhibitory effect on pathogen and pest infestations. In a field trial, we compared yields, pest, and pathogen abundance in an orchard consisting of four plots, where two plots were covered with anti-hail net covers, one with plastic rain shields only, and one with plastic rain shields and exclusion netting. Pests and pathogens were assessed visually, and beating tray samples were collected to compare overall arthropod diversity between plots. We observed virtually no scab infections in both plastic rain shield plots, despite a more than 70% reduction of fungicides applied, when compared to anti-hail plots. Although no codling moth insecticides were sprayed in the plot with exclusion netting we found significantly reduced damage here, when compared to the anti-hail plots. However, likely due to microclimatic changes, we observed an increase of powdery mildew, woolly apple aphids, and spider mites under plastic rain shields. Modeling of metabolic rates of arthropod herbivores and predators revealed that there is an increased potential of herbivory under plastic rain shields. However, in terms of plant protection, the net effect of plastic rain shields and exclusion netting was a substantial reduction in chemical pesticide use, demonstrating that they represent a promising approach to minimize the use of chemical pesticides in apple production.
The potential of farnesene isomer mixtures to support the control of aphids in the cultivation of lettuce crops
(2025) Kuhn, Denise; Bauer, Philipp; Tolasch, Till; Petschenka, Georg; Steidle, Johannes L. M.; Kuhn, Denise; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany; Bauer, Philipp; Department of Applied Entomology 360 C, Institute of Phytomedicine, University of Hohenheim, 70599, Stuttgart, Germany; Tolasch, Till; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany; Petschenka, Georg; Department of Applied Entomology 360 C, Institute of Phytomedicine, University of Hohenheim, 70599, Stuttgart, Germany; Steidle, Johannes L. M.; Department of Chemical Ecology 190 T, Institute of Biology, University of Hohenheim, 70599, Stuttgart, Germany
(E)-ß-farnesene (EBF) acts as an alarm pheromone of many aphid species and is also used as an aphid repellent by plants. Upon perception of EBF, aphids exhibit avoidance behavior. They walk away, stop feeding or drop from leaves. Moreover, EBF is an attractant for natural enemies of aphids. However, EBF is not used in pest management because it is expensive in its pure form. Therefore, we assessed the effect of a less expensive farnesene isomer mixture (FIM) on Myzus persicae (Sternorrhyncha: Aphidiae) on lettuce ( Lactuca sativa var. Ulmo) in the laboratory and under field conditions. First, we tested under laboratory conditions if FIM has the same effect on M. persicae as it is described for pure EBF. The aphids were influenced by EBF. They stopped feeding, withdrew their stylets, went away from the danger zone, or developed and reproduced more slowly. Therefore, we studied the behavioral response of the aphids after FIM application and aphid reproduction under permanent exposure of FIM. Second, we tested in the field the reaction to FIM either directly applied to lettuce or released by dispensers. In the lab experiments, we found that M. persicae reacts to FIM by walking away and that reproduction tends to be reduced in the presence of FIM. In the field, we found lower numbers of aphids in the treatments with FIM. In particular, dispenser application caused higher aphid reduction compared to spray application on lettuce. In addition, more natural enemies of aphids could be found in dispenser-treated plots. Taken together, these results indicate that the use of FIM could contribute to insecticide-free aphid control in lettuce, but possibly also in other crops.
Reducing pesticide use in apple orchards through biological control and mechanical barriers
(2025) Bischoff, Robert Thomas; Petschenka, Georg
With over 20 applications per year, apple is the most pesticide-intensive crop in Germany. Growers are under increasing pressure as the use of pesticides in agriculture comes under greater scrutiny, resulting in more restrictive legislation and a national action plan that calls for a significant reduction in overall pesticide use. Current reduction efforts are largely based on Integrated Pest Management (IPM), which essentially means that all non-chemical plant protection measures, including cultural practices, pest monitoring and biological control, should be used first, and only if pest problems persist is the use of chemical pesticides justified. While there are successful examples of IPM in fruit growing, such as the use of sexual pheromones and granuloviruses to control the codling moth, chemical control remains the dominant means of plant protection. Therefore, considering current political developments, there is a worrying lack of non-chemical control strategies for many important pathogens and pests in apple growing. In this doctoral thesis, we investigated non-chemical alternatives for pest and pathogen control in apple growing and their potential as IPM approaches. The aim was to identify new methods that would provide growers with a realistic alternative to chemical pesticides. We focused on conservation and augmentation biological control and physical methods to assess their potential for reducing pesticide use in apple production. Conservation biological control aims to enhance the biological control of pests by natural enemies and is influenced by a wide range of factors. We investigated the role of predator density, spatial complexity of apple branches and the provision of alternative food resources for predators for the effective control of apple pests. Predator density and the spatial environment of apple branches were crucial components influencing the efficacy of earwig predation on woolly apple aphids. On spatially complex branches, low and medium densities of earwigs failed to fully locate and consume woolly apple aphids, while high earwig densities were able to eradicate woolly apple aphids, including those hidden in spatially complex environments. Provisioning of additional food was investigated using predatory mites and their prey (such as apple rust mites) as a model system. Predatory mites are suspected to be prone to starvation, especially when prey is scarce. To avoid starvation and boost their populations, trees were sprayed with brine shrimp cysts, which are readily accepted as food by omnivorous predatory mites. Although no increase in predatory mites was observed, reduced populations of apple rust mites were found in plots sprayed with shrimp cysts. Other orchard predators, such as predatory flower bugs, may have been promoted and thus mediated the reduction in apple rust mites. In the same trial, the effect of an augmentative release of a predatory mite species naturally occurring in orchards was investigated. No clear effect of the predatory mite release on pest mite populations could be detected. Physical control measures are widely used in fruit growing to protect fruits from abiotic and biotic damage. While anti-hail nets are the dominant cover system used in apple orchards, plastic rain shields and exclusion nets have gained importance due to their ability to prevent scab infections and codling moth immigration, respectively. We compared chemical plant protection regimes under different cover systems, namely anti-hail nets, plastic rain shields, and plastic rain shields combined with exclusion nets, in an apple orchard. Fungicide and insecticide use could be drastically reduced under plastic rain shields and within the exclusion nets, respectively. However, due to microclimatic changes, powdery mildew and secondary pests increased in plots covered with plastic rain shields and plastic rain shields combined with exclusion nets. Despite these side effects, total pesticide use was substantially reduced in the new cover systems without incurring yield losses. These results show that a combination of conservation biological control focusing on predatory earwigs and physical control utilizing plastic rain shields and exclusion nets could be a promising approach to reduce pesticide use in apples. However, the increased costs of new plastic rain shields and exclusion nets compared to traditional anti-hail nets present a major obstacle to their large-scale adoption, and it remains unclear how apples could be produced economically using this approach.
Sensor-guided mechanical weed control in transplanted lettuce and cabbage
(2025) Gerhards, Roland; Spaeth, Michael; Heyn, Alexandra; Saile, Marcus
Effective weed control is extremely important in vegetable production because weeds affect yield and quality of vegetable crops. Usually, only combinations of preventive and direct weed control methods can sufficiently suppress weeds. Therefore, costs for weeding are much higher in vegetables compared to most arable crops. Due to restrictions for herbicide use in vegetables, alternative and efficient direct weeding methods are urgently needed. Six field experiments with transplanted cabbage and lettuce were conducted in Southwestern Germany to quantify the weed control efficacy (WCE) and crop response of sensor-guided mechanical weed control methods with different degrees of automation. A camera-guided inter-row hoe with automatic side-shift control alone and combined with intra-row finger weeders and a camera-guided intra-row hoeing (robot) were compared to standard mechanical weeding, a broadcast herbicide treatment and an untreated control. Weed densities prior to treatment averaged 58 plants m −2 in cabbage and 18 plants m −2 in lettuce. Chenopodium album, Amaranthus retroflexus, Thlaspi arvense, Solanum nigrum and Digitaria sanguinalis were the dominating species. Until harvest, 80% weed coverage was measured in the untreated plots of cabbage and 28% in lettuce, which caused 56% yield loss in cabbage and 28% yield loss in lettuce. The highest WCE was achieved with the robot (87% inter-row and 84% intra-row) The broadcast herbicide treatment achieved 84% WCE for both inter-row and intra-row areas. Conventional inter-row hoeing had the lowest WCE of 73% inter-row and 35% intra-row. Camera-guided inter-row hoeing increased inter-row WCE to 80% and intra-row WCE to 56%. Finger weeding increased intra-row WCE in lettuce and cabbage to 54% with conventional hoeing and 62% with camera-guided hoeing. Camera-guidance reduced crop plant losses by 50% (from 9.1 to 4.5%) and increased crop yield by 13% compared to conventional hoeing. This study highlights the benefits of camera-guidance, AI-based weed detection and robotic weeding in transplanted vegetable crops.

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