Herbicidal activity of allelochemical 2,4-di-tert-butylphenol on weeds (Asystasia gangetica, Eleusine indica, Leptochloa chinensis and Oldenlandia verticillata)

This glasshouse study aimed to determine the herbicidal activity of allelochemicals 2,4-di-tert-butylphenol (2,4-DTBP) on test weeds (Asystasia gangetica, Eleusine indica, Leptochloa chinensis and Oldenlandia verticillata) and to find the tolerance of test crops (Brassica rapa, Oryza sativa, Zea mays) to 2,4-DTBP. The 2,4-DTBP applied at 7 kg ai/ha inhibited the weeds seedling growth by 15-40 % only, showing its poor post emergence herbicidal activity. In contrast, soil bioassay confirmed pre-emergence herbicidal activity of 2,4-DTBP that reduced the seedling growth of weeds (L. chinensis, E. indica and O. verticillata) by 50-80 % at 2.5 kg ai/ha but A. gangetica was tolerant to 2,4-DTBP even at 5 kg ai/ha. Crop tolerance test revealed that Zea mays was tolerant to 2,4-DTBP. In contrast, root lengths of transplanted Brassica rapa seedlings and Oryza sativa seedlings were reduced by 10-15 % at 2,4-DTBP doses of 1.25 to 5 kg ai/ha, 14 days after treatment. However, these two crops seedlings became tolerant to 2,4-DTBP at 5 kg ai/ha, when applied 4 days after transplanting. Thus 2,4-DTBP may be developed as novel pre-emergence natural herbicide, without injuring the crops depending on their growth stages and crop species.