Degradation and transformation of a potential natural. herbicide in three soils

The methyl ester of fusaric acid (ME) is one of four toxins produced by the fungus Fusarium nygamai, which could be used as a natural herbicide agains t Striga hermonthica, a parasitic weed of sorghum and corn in a vast zone o f West and Central Africa. A laboratory study was performed to measure the degradation of ME in three soil types and under different temperature and s oil moisture conditions, so as to ascertain whether a single ME treatment w ould protect the crops against this weed during the critical phases of grow th. The results show that the persistence in all soils and under all incuba tion conditions is long enough to protect the crops for the first week of g rowth, excluding the trial at 30 degrees C in the humic soil, where the hal f-life of 6 days would require more than one treatment. A degradation produ ct of ME (butylpyridine, BP) was identified by gas chromatography/mass spec trometry and its degradation measured. The sum of ME and BP residues for th e first 7 days was almost 100% of the applied compound in all soils and inc ubation conditions, thus indicating that BP may be the only transformation product of ME at this stage.