Plant diseases in afforested crop-livestock systems in Brazil

Abstract

Integrated crop-livestock systems (ICLS) include diversified agricultural practices, like crops and animals grazing in the same area and frequently with afforestation. A return to these practices has been proposed in recent years, aiming to reach some benefits that may include a reduction in plant diseases, one of the main constraints in Brazilian crops. However, these benefits rely mainly on the resilience and the self-regulating capacity of the systems, and practical examples of the influence of ICLS on plant diseases are still scarce. The objective of the present work is to show how ICLS arrangements can reduce plant diseases. We carried out a four years investigation on soybean and corn diseases in agropastoral (AP) and agrosilvopastoral (ASP) systems, compared to a non-integrated control (CO), in a long-term field experiment established in 2006 in the region of Campos Gerais, Paraná state, Brazil. The tree component of the ASP system was eucalyptus and silver oak. Soybean and corn were cultivated alternately as summer crops, and the natural occurrence of diseases evaluated from 2012 to 2015 sowings. Results show that the agricultural diversification promoted by ICLS can reduce foliar diseases intensity, and the ASP system showed the best results. The rust severity was 28.2 and 34.2% in ASP and AP systems in 2012, and 8.5 and 12.4% in ASP and AP in 2014. White-spot severity was 1.6, 2.2, and 3.1% in ASP, AP, and CO systems in 2013, and 0.6, 1.3, and 1.3% in ASP, AP, and CO in 2015. Other diseases, like downy-mildew on soybean and gray-leaf-spot on corn, were also less severe in ASP compared to other systems. Micrometeorological variables recorded inside soybean and corn canopy contributed to understanding the influence of ICLS arrangements on plant diseases, allowing concluding that microclimate is the main drive influencing disease reduction in the aerial part of crops in ICLS. The ICLS, mainly the agrosilvopastoral system, pose as a less diseases susceptible and consequently an environmentally friendly system. Knowing the requirements of the pathogens of a crop species is fundamental in planning a production system, avoiding or minimizing risks. The influence of trees on plant diseases of afforested production systems is discussed.