The objective of this work was to evaluate the effects of crop cover, using Brachiaria ruziziensis mulch, Trichoderma harzianum 1306 spray treatment and of the interaction between these methods in reducing the density of Sclerotinia sclerotiorum inocula, in white mold incidence and in soybean yield. The evaluations were done from 2006 to 2008 in Jataí (Goiás State, Brazil), in a commercial crop with an average of 136.08 sclerotia m-2. In March and October 2006, 0, 0.5, 1 and 1.5 L ha-1 of T. harzianum 1306 (2x10(9) viable spores mL-1) were sprayed on plots cropped with B. ruziziensis or not. After controlling brachiaria with glyphosate (2,5 L ha-1) and sowing soybean 'M-Soy 6101' onto 10.1Mg ha-1 of its straw, 98% less apothecia were found in these treatments. The treatments with straw and 0.5 and 1 L ha-1 of T. harzianum presented 72.1 and 84.1% more parasited sclerotia respectively. 'M-Soy 6101' soybean yield in 2006/2007 was inversely proportional to the apothecia population per square meter, but 7.6% lower in the treatments with straw. In the 2007/2008 season, the disease incidence in 'M-Soy 7908' was lower in plots with straw and 0.5 and 1 L ha-1 of T. harzianum 1306, applied only in the previous year. Biocontrol with T. harzianum 1306 and the use of B. ruziziensis mulch are efficient and viable for white mold control in soybean in Brazilian Cerrado areas.
Glycinemax; Sclerotinia sclerotiorum; Brachiaria ruziziensis; biological control; cultural control
