Evaluation of weed control potential of meadowfoam (Limnanthes alba Benth.) plant

We studied the effects of defatted seed meal of meadowfoam on weed control, but not of other plant parts (leaves, stems, flowers and roots). There were no differences among the extraction methods (water, boiling water, ethanol and fermentation) and plant parts (leaves, stems, above ground parts, seeds and defatted seed meal) in I50 values for germination, shoot and root lengths of cucumber and barley. The I50 and I90 values for shoot and root lengths of Echinochloa oryzicola Vasing, Digitaria ciliaris Koel, Artemisia princeps Pamp., Cirsium japonicum var. Maackii Matsum and Taraxacum platycarpum Dahlst were lower in leaves, stems, above ground parts, seed meal and defatted seed meal extracts than in flowers and roots. Broad leaf weed species (A. princeps, C. japonicum, and T. platycarpum) were more sensitive to water extracts of tested plant parts than grassy weeds (E. oryzicola and D. ciliaris). T. platycarpum was completely controlled by soil application of stems and defatted seed meal at 600 g/m2 and was 95% controlled by seed meal at 600 g/m2. Other weed species (E. oryzicola, D. ciliaris, A. princeps and C. japonicum) were 62-91% controlled by stems, seed meal and defatted seed meal at 600 g/m2. However, total phenol and flavonoid contents may not be related to herbicidal mechanisms in plant parts of meadowfoam. Germination rates, shoot and root lengths of barley and cucumber in n-hexane solvent fraction were more inhibited than in chloroform, ethyl acetate, butanol and water fractions. A herbicidal compound, 3-methoxyphenyl acetonitrile, was found present at higher levels in the n-hexane fraction than other fractions. Application of 3-methoxyphenyl acetonitrile at 0.1% completely inhibited the germination, shoot and root lengths of lettuce, E. oryzicola and C. japonicum. Thus, meadowfoam leaves and stems as well as defatted seed meal can be used for weed control on organic farms.