Rejection of Fusarium pallidoroseum as a Biological Control Agent of Mimosa invisa in Upland Rice

Abstract

Fusarium pallidoroseum , isolated from diseased Mimosa invisa in the Philippines, provided excellent control of M. invisa seedlings when applied as a foliar spray of the crude culture filtrate in laboratory and field trials. The effect was immediate contact action, causing rapid desiccation of treated tissues because of the production of toxin(s). The cell-free filtrate of F. pallidoroseum was more virulent than the crude filtrate. Seedlings at the cotyledon stage and older 3- to 4-leaf seedlings escaped the phytotoxin action of F. pallidoroseum and regrowth occurred. Inoculum was readily produced on milled rice and remained virulent for at least six months under room condition storage. Culture filtrates of F. pallidoroseum caused disease symptoms on a broad range of plant species. Most plants, however, expressed only light infection, while Mimosa invisa , M. pudica and Cucumis melo (cantaloupe) were severely damaged by the isolate. Symptoms were observed on some upland rice cultivars, but affected rice plants outgrew the effects. Mycotoxins are produced by isolates of F. pallidoroseum , but the health risk associated with the use of F. pallidoroseum as a weed control tool is not known. Until the health risk is known and documented, the possible use of F. pallidoroseum as a control strategy for M. invisa should be deferred.