The effects of tillage, irrigation (10 cm each at 10- to 14-leaf stage, and silking and milk stages, and no supplemental irrigation) and fertilizer (NPK at 0:0:0 or 140:40:0 kg/ha) treatments on the incidence of lepidopteran insects and fungi infesting maize (cv. Pioneer 3025W) were studied in Tamaulipas, Mexico, during 2005-07. The tillage treatments consisted of mouldboard ploughing (discing stalks after harvesting, followed by mouldboard ploughing, discing and row establishment), subsoil-bedding (shredding stalks after harvesting, followed by subsoiling on row centres and establishment of beds), shred-bedding (shredding stalks after harvesting, followed by bedding on old rows), and no-tillage (shredding stalks after harvesting, and spraying 0.6 kg glyphosate and 0.72 kg 2,4-D/ha twice for weed control). Mouldboard ploughing represented conventional tillage, whereas subsoil-bedding and shred-bedding were reduced tillage systems. The lepidopteran species recorded were Helicoverpa zea (86%) and Spodoptera frugiperda (14%). The incidence of these pests was highest in 2006 (91.5%) and lowest in 2007 (49.3%). The most common fungi were Fusarium spp., the highest incidence of which was registered in 2005 (24.4%). The incidence of Aspergillus flavus and Ustilago maydis [ U. zeae] was less than 4.0% regardless of the year. The incidence of lepidopterans significantly varied between the irrigation levels only (greater pest population under dryland farming). Fusarium spp. and A. flavus occurred more frequently under no-tillage compared with other tillage practices. The incidence of Fusarium spp. was higher in irrigated than in dryland maize.
