PERFORMANCE OF TRICHOTROPICO, MIX OF THE FUNGI Trichoderma harzianum AND T. koningii IN THE CONTROL OF Rhizoctonia solani, CAUSAL AGENT OF THE HUSK DISEASE IN RICE CROP.
The rice husk disease caused by the fungus Rhizoctonia solani is considered one of the most restrictive diseases in the rice productivity of Asia, United States and other countries. In Colombia, its incidence and severity has increased during the last years, causing lost that represent 40% of the total weight of grains for rice panicle, and there are not tolerant rice varieties to this pathogen fungus in the world.
As considering the registered potential of Trichoderma spp. in the control of R. solani throughout different mechanisms, the efficacy of TRICHOTRÓPICO was evaluated in foliage preventive sprayings, starting from the maxim budding period before the sprouting of the panicle, stage where the presence of the pathogen is more common and its damage is more severe.
A wettable powder formulation of TRICHOTROPICO, at 5 x108 spores/gram concentration, three doses of commercial product and different application times in two different environments was evaluated. To measure the severity grade of the husk disease, the scale of the International Rice Research Institute, IRRI was recommended, which is based on the relative high of the damage; moreover, for each site where the disease was located, the covered area of affected plants was calculated and it was employed as efficacy parameter; results were submitted to the variance analysis and the Duncan test to establish the statistics differences, as well as the relative effectiveness (% RE) of the treatments throughout the Abbot formula.
According to the results at field conditions in which trials were done, the following conclusions and observations can be established:
The antagonistic fungi T. harzianum y T. koningii in the TRICHOTROPICO product were effective for the management of the husk disease, at low or high incidence conditions, and at foliage spraying of 750 y 1000 g/ha doses. No differences between doses were found as severity and productivity values supported the product efficacy on the husk disease.
It is necessary to start the treatments with TRICHOTROPICO as a preventive form of management of the disease, to let the fungi to establish and spread the soil at field conditions. Likewise, it is recommended an inundative spraying for the first application, at 1000 g/ha, continuing with periodic sprayings each ten days of lower doses: 500 y 750 g/ha, depending on the incidence and severity levels and climatic conditions than promote R. solani pathogen.