Relação entre datas de sementeira e os diferentes patógenos da cultura do girassol -helianthus annuus l em Umbelúzi

Abstract

The degree work presented here is the result of an observation made in the field for the cultivation of sunflower, in the free-pollinated varieties, ALA and RECORD, hybrid varieties, "PAN7392", "2W2302", for two years (period 1997/1998) . The main objectives were to identify the sowing dates with the lowest and highest attack by the most harmful parasites for the sunflower crop and to analyze the behavior of free-pollinated and hybrid varieties in relation to pathogen attacks. Thus, the behavior of four diseases that affect the sunflower crop in Mozambique, namely, Puccinia helianthi, Alternaria hellanthl, Alternaria alternata and Sclerotium batalicola, was analyzed. A randomized complete block design with a 7x4 factorial nested arrangement was used for the treatments, with two replications. In this drawing the varieties were contained in the planting dates. The sunflower crop in its different varieties was susceptible to pathogens' attack and the best date for sowing varies according to the type of pathogen, with August and November being the most flowering months for Puccinia helianthi, September for Alternaria alternaia, August for Alternaria helianthi and November for Sclerotium batticola. The incidence of P. helianthi was lower than that of other diseases, with an infection rate of 0.41. S. balaticola had the highest percentage of ataque (27.25%).