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

Cenchrus setaceus 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, Artemisia thuscula and Plocama pendula, on Cenchrus setaceus 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 (w:v) leaf-to-water ratio, using C. setaceus and Lactuca sativa under growth chamber conditions. In the validation trial, lixiviates prepared at a 1:6 (w:v) ratio were applied directly to C. setaceus and seven crops (Zea mays, Allium cepa, Hordeum vulgare, L. sativa, Solanum lycopersicum, Brassica oleracea, and Raphanus sativus) 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, C. setaceus germination was inhibited by up to 60% by both ratios of lixiviates (Dunn p < 0.05), with reduced speed and seedling growth (plumule: -37.5%; radicle: -85%). Crop sensitivity varied: A. cepa and H. vulgare showed no significant inhibition; B. oleracea and R. sativus were affected by P. pendula (germination reduced 2.5-2.7×); and Z. mays, L. sativa, and S. lycopersicum exhibited delayed germination and reduced seedling growth under both treatments. These results support the selective use of native plant lixiviates for integrated management of Cenchrus setaceus in sensitive agroecosystems.