This study evaluates the interaction effects on corn (Zea mays L.) growth between intact humic substances (HS) extracted in an alkaline medium from three different origins (an Organosol [HS-Org], an Andisol [HS-And], and vermicompost [HS-Vc]) and the arbuscular mycorrhizal fungus (AMF) Dentiscutata heterogama. The HS were characterized by spectroscopic techniques, and different biochemical, morphological, nutritional, and AMF colonization parameters were evaluated in corn plants. The experiment was conducted in a greenhouse, and low-fertility soils sterilized after solarization were used as the substrate. Hybrid corn BR-3025 was planted, and the HS concentrations used were 5, 10, and 20 mg carbon L −1 for HS-And, HS-Vc, and HS-Org, respectively, applied 15, 25, and 45 d after emergence close to the roots. The results show that HS application and D. heterogama inoculation significantly stimulated the biomass in relation to the treatments without AMF. Carbohydrate and protein content were stimulated by HS-AMF interaction. A higher leaf content of nutrients was observed in the AMF-and HS-inoculated plants. The HS-Vc application and AMF inoculation resulted in intense stimulation, which was confirmed with a high mycorrhizal efficiency. The spore density and glomalin content were also stimulated by the three different HS applications independently of their source. The HS-Vc has intermediate structural chemical characteristics in terms of polarity and aromaticity compared with HS-Org and HS-And. The HS-Vc more strongly stimulated the plant physiological parameters when combined with the AMF inoculation. These results may indicate that the HS formed in soil and characterized by structures that are more balanced may function more effectively.

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El uso de enemigos naturales para el control de insectos plaga como Spodoptera frugiperda en el cultivo de maíz constituye una alternativa viable que reduce considerablemente el impacto ambiental de la agricultura moderna, caracterizada por el uso de agrotóxicos. El objetivo del presente trabajo fue evaluar la eficiencia de Trichogramma sp en el control de Spodoptera frugiperda en el cultivo de maíz. El experimento se instaló en la comuna San Marcos, en el cultivo de maíz híbrido Hércules; se estableció un diseño experimental completamente al azar con arreglo bifactorial 2x3, donde un factor fue la densidad del parasitoide (100.000 ind∙ha−1(D1)) y 200.000 ind∙ha−1(D2)) y el segundo factor, tres tiempos de liberación (TL) 30, 45 y 60 días después de la germinación (DDG), con cuatro repeticiones. Los datos fueron analizados en el programa estadístico SISVAR, las medias comparadas utilizando el test de Tukey con un 95 % de confianza. Se evaluó incidencias (I), grado de afectación por cogollero (GAC) y masa de huevos parasitados (MHP). Los resultados demuestran que el tiempo de liberación afecta directamente a las variables I y GAC, mientras que la variable MHP se relaciona con el tiempo de liberación y la densidad. Entre las tres variables estudiadas sobresale la liberación temprana se intensifica a mayores densidades del parasitoide.

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