# Natural Salicylaldehyde for Fungal and Pre- and Post-Emergent Weed Control
###### Abstract  
A sustainable, alternative weed control strategy is developed using salicaldehyde (SA; 2-hydroxybenzaldehyde) as an active ingredient. SA is a natural, redox-active small molecule listed as a Generally Recognized As Safe food additive by the European Food Safety Authority and the United States Food and Drug Administration. The repurposing of SA determined that SA possesses both pre- and post-emergent herbicidal, fumigant activity, where the emitted SA from the source completely prevented the germination of plant seeds and/or the growth of the germinated plants. As a proof-of-concept, we developed agricultural byproducts (tree nutshell particles) as SA delivery vehicles to the soil, thus helping the growers' sustainable byproduct recycling program, necessary for carbon sequestration. In plate assays, SA emitted from the nutshell vehicles (0.15 to 1.6 M) completely prevented the germination of six invasive or native weed seeds (monocots, dicots). In Magenta vessel assays, SA emitted from the nutshell vehicles (0.8 to 1.6 M) not only prevented the germination (pre-emergent) of _Lagurus ovatus_ (Bunny Tails Grass) seeds but also inhibited the growth (post-emergent) of the germinated weeds. We determined further that soil covering (soil pasteurization) could be one of the practices to effectively deliver SA to the soil, whereby 1.6 M of SA emitted from the nutshell vehicles prevented the germination of the _L. ovatus_ seeds maintained in soil trays covered with plastic tarp at 22 \"C, while 0.8 M SA allowed partial (15%) germination of the weed seeds. Of note, SA also possesses an intrinsic antifungal activity that overcomes the tolerance of the stress signaling mutants of filamentous fungal pathogens (_Aspergillus funjgatus_, _Penicillium expansum_) to the phenylpyrrole fungicide fluidoxosil. Environmental degradation data available in the public database indicate that, once released to the environment, SA will be broken down in the air by sunlight or microorganisms and, thus, is not built up in aquatic organisms. Altogether, SA can serve as a safe, potent pesticide (herbicidal, fungicidal) ingredient that promotes sustainable crop production by lowering the pesticide burden in fields. g Agricultural byproducts; fluidoxonil; fungal pathogens; herbicides; natural compounds; pre-emergent; post-emergent; salicaldehyde; soil pasteurization; weeds +
Footnote †: journal: Applied Sci. that termination of herbicide usage during crop cultivation triggered unexpected increases in mycotoxin contamination in the grains, with near maximum threshold levels for nilvalenol [1]. The study identified that the uncontrolled weeds in the crop fields functioned as _Fusarium_ reservoirs/spillovers, thus highlighting the importance of adequate weed control practices for assuring public food safety as well as food security. Therefore, the rapid elimination of weeds via safe, cost-effective methods will positively impact the safety, quality, and competitiveness of agricultural commodities. However, there are emerging issues with the current uses of conventional herbicides, including: (1) the increasing negative perceptions of the public towards conventional herbicides such as glyphosate (\(N\)-(phosphonomethyl) glycine), a broad-spectrum post-emergent herbicide [2], (2) the development of weed resistance to commercial herbicides [3], (3) the European Union's (EU's) new policy in lowering maximum residue limits against paraquat (pulmonary toxicity) and glufosinate (reprooxicity) (European Food Safety Authority (EFSA) [4; 5; 6]), and (4) the cancellation of the registration of toxic seed-disinfecting fungicides such as Ferbam (iron tris (dimethyldithiocarbamate)) and Ziram (zinc dimethyldithiocarbamate) (Pest Management Regulatory Agency [7]). Moreover, certain herbicides and fungicides, such as glyphosate and azoles (tebuconazole, propiconazole), respectively, trigger severe toxicity to non-target organisms, including bees, when they are applied in combination [8; 9].