White grub incidence, Campesino management systems and climatic variability in Napizaro, Michoacán, México

Abstract

Traditional agriculture continues to be an important practice in Mexico, however it is not homogeneous and presents a great diversity of managements that is reflected on crop yield and biodiversity maintenance. In recent times, due to excessive use of pesticides and the increase in monocultures, pest species have become and important problem. Particularly soil pest are causing annual losses; however evidence to decide which management strategies minimize pest effects upon harvest is lacking. In order to estimate the effect of management type upon white grub abundance, we evaluated three management systems in the community of Napizaro in the Pátzcuaro basin, Mexico. The studied systems were: conventional management, organic fertilization and crop rotation, in four different plots per system. In three consecutive years (2010-2012) during the agricultural cycle between June and December, we sampled white grub abundance once per month and we evaluated crop yield per hectare at the end of the season. Also we measured soil parameters such as pH and percent organic matter per plot. The evaluated plots present a management gradient that is reflected on white grub abundance and on maize yield. Organic fertilized and crop rotation plots presented lower abundances of soil pests in comparison with conventional plots (p<0.05), while crop yield was greater in conventional plots. On the other hand, soil parameters showed that organic fertilization indeed increased % soil organic matter and soil pH reached more adequate levels in crop rotation plots. White grub abundance was not related with crop yield, therefore we suggest further investigation into the direct effect of these insects upon maize plants. Organic fertilized and crop rotation plots where resilient to drought effects, particularly regarding white grub abundance.