Searching for natural herbicides in methanol extracts of eight plant species

Background Plant extracts could turn out to be natural herbicides to be used in weed control. This study was conducted to study the phytotoxic effects of methanol extracts obtained from Tamarix mannifera, Alhagi maurorum, Echinops spinosissimus, Haloxylon salicornicum, Lactuca virosa, Neurada procumbens, Ochradenus bacctus, and Cyperus conglomerates plants on germination and growth of Phalaris minor, Echinochloa crusgalli, Portulaca oleracea, and Lactuca sativa. Results In laboratory trial, extracts of eight plants at 0, 5, 10, 20, and 40 g/L were evaluated on germination of seeds of four target species. The inhibitory effect of tested extracts varied among the examined seeds, and P. minor was the most sensitive. Extracts of T. mannifera and L. virosa showed the greatest effect on seed germination and seedling growth of studied seeds. Using the extract of T. mannifera at 40 g/L completely inhibited the germination and seedling growth of P. minor and shoot length of P. oleracea as well as root length of E. crusgalli and L. sativa. At this concentration, L. virosa nearly had a complete inhibition effect on germination and seedling growth of P. minor and P. oleracea. In the greenhouse trial, extracts from tested plants at four concentrations (0, 30, 60, and 90 g/L) were used in a phytotoxic bioassay against 6-week-old L. sativa and three target weeds. The growth of 6-week-old weeds tended to be less sensitive to the tested extracts than the weed germination. The significant injury effect was observed only when T. mannifera extract at 60 and 90 g/L was sprayed on P. minor, E. crusgalli, and L. sativa plants. Conclusions Among tested species, T. mannifera and L. virosa could be used for developing new natural herbicide.