Allelopathic Effects of Artemisia thuscula and Plocama pendula on the Invasive Plant Cenchrus setaceus and Crops

<i>Cenchrus setaceus</i> is an alien invasive species with significant ecological impact on both natural ecosystems and agricultural areas across the Canary Islands. In this study, we evaluated the allelopathic effects of foliar lixiviates from two endemic species, <i>Artemisia thuscula</i> and <i>Plocama pendula</i>, on <i>Cenchrus setaceus</i> and a group of crop species to assess (i) germination inhibition of the invasive species and (ii) selectivity towards non-target crops. A preliminary trial tested undiluted and diluted forms (1%, 10%) of concentrated lixiviates prepared at a 1:3 (<i>w</i>:<i>v</i>) leaf-to-water ratio, using <i>C. setaceus</i> and <i>Lactuca sativa</i> under growth chamber conditions. In the validation trial, lixiviates prepared at a 1:6 (<i>w</i>:<i>v</i>) ratio were applied directly to <i>C. setaceus</i> and seven crops (<i>Zea mays</i>, <i>Allium cepa</i>, <i>Hordeum vulgare</i>, <i>L. sativa</i>, <i>Solanum lycopersicum</i>, <i>Brassica oleracea</i>, and <i>Raphanus sativus</i>) under both growth chamber and greenhouse conditions. Germination indices were calculated across assays, and plumule and radicle lengths were measured in growth chamber assays. In both trials, <i>C. setaceus</i> germination was inhibited by up to 60% by both ratios of lixiviates (Dunn <i>p</i> < 0.05), with reduced speed and seedling growth (plumule: -37.5%; radicle: -85%). Crop sensitivity varied: <i>A. cepa</i> and <i>H. vulgare</i> showed no significant inhibition; <i>B. oleracea</i> and <i>R. sativus</i> were affected by <i>P. pendula</i> (germination reduced 2.5-2.7×); and <i>Z. mays</i>, <i>L. sativa</i>, and <i>S. lycopersicum</i> exhibited delayed germination and reduced seedling growth under both treatments. These results support the selective use of native plant lixiviates for integrated management of <i>Cenchrus setaceus</i> in sensitive agroecosystems.