We investigated the phytotoxicity of desert cotton (Aerva javanica) extracts on wild oat and wheat. Aqueous extracts from A. javanica roots, leaves and inflorescences collected from Jeddah and Al-Baha regions, Saudi Arabia were used. Generally, the allelopathic potential of water extracts of A. javanica collected from Jeddah were more in inhibitory to wild oat germination and seedlings growth than those

Abstract

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.