Importancia de las plantas voluntarias de maiz como reservorio de Exserohilum turcicum (tiz¨®n foliar com¨²n) y Kabatiella zeae (mancha ocular)

FORMENTO, A.N.; PIOLI, R.; PLOPER, L. D.

Rosario

Congreso; Maiz HD - X Congreso Nacional de Maiz.; 2014

Asociacion de Ingenieros Agronomos del Norte de Buenos Aires

Current corn production in Argentina is characterized by zero tillage, insufficient crop rotationand inadequate management of volunteer plants, mostly corn RR. The increase of late planting (December-January) has allowed the re-emergence of foliar diseases and ears and stalks rots, standing out the northern leaf blight (NLB) caused by Setosphaeriaturcica, anamorph Exserohilumturcicum, eyespot (ES) by Kabatiellazeae, gray leaf spot (Cercosporazea-maydis) and southern rust (Pucciniapolysora). The necrotrophic pathogens survive in stubble and volunteer plants, which have become an important source of initial inoculum. The NLB can cause losses greater than 40% and ES up to 9%. The aim of thisstudy was to evaluate the occurrence of NLB and ES in volunteer corn plants in Entre Rios province. About 26 fields located in Paraná, Diamante, Victoria, La Paz and Federal were assessed between June 2 and July 3,2014. The following variables were considered: previous crop, total number of volunteer plants, volunteer plants per m-2, growth stage, prevalence, incidence and severity of diseases. About 35% of fields were planted after corn, 27% after wheat and 23% after soybean;85% of fields in zero tillageand 15% in reduced tillage. We analyzed 897 plants and an average of 9 volunteer plants by m-2was determined; 41.9% of the volunteer plants were in V6 and 25.9% in V5. NLB prevalence was 100% and ES prevalence was 88.5%, with an incidence of 99.4 and 97.2%, respectively. NLB severity was over 25% (high level) and ES 9% (moderate level). The inadequate chemical control and mild temperaturesin the winter, favor the presence of volunteer plants, considered an important "green bridge" between corn growing seasons.