Combination of a mycoherbicide with selected chemical herbicides for control of Euphorbia heterophylla

摘要

The leaf-spot fungus Lewia chlamidosporiformans is being developed as a mycoherbicide for wild poinsettia (Euphorbia heterophylla), a serious weed of many crops, and particularly of soybeans, in Brazil. A comparative study of the levels of control ofwild poinsettia obtained for the fungus alone, the fungus plus selected herbicides and these herbicides alone was undertaken. The levels of control obtained with application of the fungus alone was equivalent to the chemical herbicides fomesafen, carfentrazone and atrazine for plants with up to five leaves, and equivalent to the herbicide glyphosate for plants with five to ten leaves for one of the weed populations being tested. The fungus alone had a better performance than both imazethaphyr and fomesafen. The combination of fomesafen with the fungus produced complete control for the three weed populations, whereas its combination with imazethaphyr significantly improved the control levels as compared with those obtained with imazethaphyr alone. Another experiment performed in microplots in the field, explored the combination of Z,. chlamidosporiformans with fomesafen and clorimuron-ethyl for the control of an imazethaphyr-resistant biotype of the weed. The best control levels were achieved with theapplication of an equivalent of 300 1/ha of a suspension of conidia (2.5 x 105 conidia/ml) in a solution of fomesafen (25% of recommended dose). Death of all plants resulted from such application after 10 days.