Influência de diferentes densidades de semeadura de adubação verde nas injúrias provocadas por spodoptera frugiperda (Lepidoptera: noctuidae) em plantio direto de milho (Zea mays)

Abstract

The cultivation of corn holds significant importance for farmers, and in the pursuit of more sustainable farming practices, direct planting systems have been developed. This study aimed to assess the impact of different densities of cover crops on the injuries caused by the fall armyworm (Spodoptera frugiperda) in corn (Zea mays) cultivation. The experiment took place in a previously fallow area with initial cultural treatments, including soil preparation, correction, and fertilization. Cover crops used were a policulture of Avena strigosa, Raphanus sativus, and Vicia villosa, with treatments at densities of 0, 40, 80, 100, 120, and 160% from recommendation. Monitoring of fall armyworm-induced defoliation was visually conducted over 19 weeks, beginning at the V2 phenological stage up to the R4 stage of corn. Statistical analysis revealed no significant difference in the population pressure of the fall armyworm among different densities of green manure. This outcome could be attributed to the prior fallow condition of the area, the prevalent presence of Urochloa decumbens. In surrounding areas, and a period of regular rainfall during the corn cycle, which might have directly influenced the population pressure of the armyworm. Regarding corn production, significant results were observed in the plots, with the treatment achieving the highest production at 100% green manure, yielding 4,237 kg ha-1. However, it is acknowledged that corn crops can attain higher yields, and lower production might be associated directly with nutrient availability in a fallow area, potentially impacting first-year plantings. The treatment with 80% green manure yielded lower results than the plots with 0% and 40% green manure, rendering this outcome inconclusive. Thus, it can be concluded that the injuries caused by S. frugiperda in corn crops did not differ among the treatments. However, the productivity did differ among the treatments.