Seed treatment is an attractive method for applying antagonistic
microorganisms, as other methods involve the application of
larger amounts of propagules. However, the survival of the BCAs
in the soil after the application is essential for the efficient control
of the pathogen. According to Hoitink and Boehm (1999), the selection
of BCAs able to colonize the host rhizosphere or the introduction
of a food base allows the preferential colonization of the soil
and rhizosphere by the BCAs. In previous studies, Gava and
Menezes (2012) demonstrated that Trichoderma spp. isolates used
in the present work were able to colonize the rhizosphere of melon
plants actively, controlling soil-borne plant pathogens in field
conditions.
Melon growers intensively employ drip irrigation systems. So,
applying organic matter to extensive areas become easier when
it is in liquid form. Liquid composts are produced by the submerged
composting of organic wastes for 15 to 60 days, under aerobic
or anaerobic conditions. Liquid composts (LC) are rich in
dissolved organic matter and support a large and diverse microorganism
population (Ghorbani et al., 2005). Applying LCs directly to
the soil or shoots has resulted in the control of plant diseases in different
pathosystems (Lorito et al., 2010). Therefore, application of
BCA and liquid composts by irrigation are likely a good strategy
for soil-borne pathogen control. Considering that, the objectives
of this study were (a) to select effective Trichoderma spp. isolates
for the biological control of melon wilt and (b) to evaluate the
effectiveness of the combined application of Trichoderma spp. and
liquid compost for the biocontrol of melon wilt in naturally
infested field conditions.