Colonization of plant waste substrates by entomopathogenic and mycoparasitic fungi - a SEM study

Six plant waste substrates: palm leaves (Phoenix dactylifera, Phoenix canar iensis, Washingtonia filifera and Chamaerops humilis), Phoenix dactylifera seed and almond mesocarp, have been used to produce entomopathogenic (Verti cillium lecanii, Paecilomyces farinosus, Metarhizium anisopliae, Beauveria bassiana) and mycoparasitic (Trichoderma harzianum and Gliocladium virens) fungi. Uninoculated plant waste substrates had very little microbial coloni zation. In inoculated substrates, germinating conidia of T. harzianum were found on P. canariensis leaves. Widenings of hyphal apex, resembling appres soria, were found for T. harzianum and B. bassiana on palm leaves. Hyphae o f G. virens produced adhesives on the surface of palm leaves. The developme nt of antagonistic fungi on plant waste substrates depended on the combinat ion fungus-substrate tested. Of the entomopathogens 14 farinosus did not gr ow on almond mesocarp. This fungus grew well on both P. dactylifera seed an d P. canariensis leaves. P. farinosus grew extensively on the edges of the leaf fragments and then started colonizing the leaf surface. V. lecanii col onized and sporulated on almond mesocarp. Of all the plant waste substrates tested M. anisopliae only did grow on almond mesocarp. C. humilis leaves w ere excellent substrates for the growth and sporulation of both V. lecanii and B. bassiana. B. bassiana grew best on P. dactilyfera seed. The mycopara sitic fungi were, in general terms, faster and better colonizers of plant w aste substrates than the entomopathogens. T. harzianum and G. virens sporul ated well on P. dactilyfera seed C. humilis leaves also supported abundant growth of T. harzianum. P. canariensis leaves were also readily colonized b y the fungus. Our results show that plant waste has potential as substrate for production and perhaps formulation of important biocontrol fungi. (C) 1 999 Elsevier Science Ltd. All rights reserved.