Controle químico de Dreschlera teres (Sacc. ) shoem. da cevada

Resumo

Um ensaio de controle químico da mancha reticular, Dreschlera teres, em cevada, cv. FM 519, foi realizado na Estação Experimental de Cevada da Maltaria Navegantes S.A., em Encruzilhada do Sul, RS. Os tratamentos empregados foram duas aplicações de Propiconazole 25% CE e Triadimefon 25% PM em intervalos de 20 e 30 dias, ambos na dosagem de 125 g i.a./ha. Como critério de avaliação utilizou-se uma escala de 0 a 5 e para o cálculo da percentagem do índice de Severidade de D. teres empregou-se a fórmula:
ISD= ((a + 2b + 3c + 4d + 5e)/5.N)x100, onde:
a= n° de plantas com grau 1; b= n° de plantas com grau 2; c= n° de plantas com grau 3; d= n° de plantas com grau 4; e= n° de plantas com grau 5; N= n° total de unidades observadas e 5= grau máximo de infecção. Foram feitas quatro avaliações nos estágios da planta: 9; 10.1; 10.5.4 e 11.2 (Escala de Feeks-Large) e nas folhas 1, 2, 3 e bandeira. Propiconazole aplicado em intervalos de 20 dias determinou o menor índice de severidade de D. teres (Sacc.) Shoem, maior produção, maior percentagem de grãos do tipo I, teores de proteína dentro dos limites tolerados pela industria e maior rendimento. Abstract This experiment was conducted at the Experimental Station of the Navegantes Malting Co., located in Encruzilhada do Sul, RS. The malting barley variety used was FM 519 and the experimental design was a randomized block with four replications. The treatments were two spray applications of Propiconazole 25% EC and Triadimefon 25% W.P. in a 20 and 30 days intervals. The fungicide rate was 125 g of active ingridient per hectare. As evaluation criterium a 0-5 scale was used and in order to calculate the severity index of Dreschlera teres the following formula was used:
ISD= ((a + 2b + 3c + 4d + 5e)/5.N)x100
onde: a= number of plants rated as 1; b= number of plants rated as 2; c= number of plants rated as 3; d= number of plants rated as 4; e= number of plants rated as 5; N= total number of units observed and 5= maximum degree of infection. For evaluations at the flag leaf and leaves 1, 2 and 3 were don’t a t the plant growth stages, according the Feeks-Large scale: 9, 10.1 ; 10.5.4 and 11.2. The treatment with Propiconazole at 20 days intervals resulted in the lowest Disease Severity Index caused by Dreschlera teres (Sacc.) Shoem as well as greater percentage of type I and protein levels within the malting barley industry tolerances and greater yields.