This work reports the results of the effects of chemical control and nitrogen-potassium fertilization on gummy stem blight, one of the most important watermelon (Citrullus lanatus) diseases. Two factorial field assays were conducted in Projeto Formoso, Tocantins, in a randomized block design with four replicates. Experimental plots measured 30 x 10 m. Treatments for assay I were (factor a - active ingredients/100 l water or ha): (1) mancozeb (MANC)-160.2 ml, (2) methyl thiophanate (TM)-49 g, (3) carbendazin-500 ml, (4) tebuconazole-20 g, (5) difenoconazole (DIFE)-75 ml, (6) methyl thiophanate-40 g + chlorothalonil -100 g, (7) copper oxychlorate-168 g, (8) trifloxistrobina-87.5 g + propiconazole-87.5 g, (9) mancozeb-80 ml + difenoconazole-37.2 ml, and (10) control. Treatments for factor b were two levels of N-K fertilization: (1) 30-20, and (2) 90-60 kg/ha. Disease severity on leaves was evaluated on a 0 to 9 scale. For the assay II, treatments for factor a were repeated, while treatments for factor b were N-K fertilization levels (kg/ha) 60-40 and 120-80. On both assays, lowest Areas Under Disease Progress Curves (AUDPD), were obtained with MANC + DIFE, TM + chlorothalonil, MANC, trifloxistrobina + propiconazole and copper oxychlorate. Fertilization did not affect disease severity. Larger yields were obtained with TM + chlorothalonil, MANC + DIFE and MANC.
Citrullus lanatus; Didymella bryoniae; fungicides
