Includes bibliographical references.

Maize (Zea mays L.) is the “queen of cereals” due to its high genetic yield potential among the cereals. It is the third important food crop in world after wheat and rice. Mize contributes 39 % of the global grain production. India ranks fourth in area and sixth in production, representing around 4 % (9.3 M Ha) of the world maize area and 3 % (35.00 MT) of total production. In India, maize is grown throughout the year in a wide range of environments, extending from extreme semi-arid to sub-humid and humid regions. Maize is affected by several diseases caused by fungi, bacteria, virus, nematodes which leads to an economic loss of 13.2 %. Northern corn leaf blight caused by Exserohilum turcicum (Pass.) Leonard and Suggs which leads to a fodder and yield reduction up to 16-98 %. In the present study, the diseased leaf sample were collected from the three selected areas viz., CPGS-AS (Umiam), ICAR-RC for NEH (Umiam) and CoA (Kyrdemkulai). It was observed that the disease was severe in CPGS-AS (Umiam) and ICAR-RC for NEH (Umiam) regions when compared to CoA (Kyrdemkulai). The pathogen was isolated from the diseased leaves and identified through cultural, morphological and molecular confirmation. The studies on the efficacy of the silver nanoparticles (AgNPs) and their mode of action on the mycelium and conidia were conducted under in vitro conditions against the pathogen E. turcicum. Nine concentrations of AgNPs were tested against the pathogen by poisoned food technique and the results showed that, the effect was significantly depending on the concentration of the AgNPs. The minimum mycelial growth (1.32 cm) and maximum per cent inhibition of mycelia (85.37 %) were observed at 200 ppm (T9) followed by 150 ppm (T8) in which mycelial growth (2.63 cm) and per cent inhibition of mycelia (70.74 %) and least effect was observed at 1 ppm (T1) in which mycelial growth (7.86 cm) and per cent inhibition of mycelia (12.63 %). The studies on the mode of action of AgNPs at different concentrations on the mycelium and conidia of E. turcicum depicts distortion of the cell wall of the conidia at higher concentrations viz., 100 ppm (T7), 150 ppm (T8), 200 ppm (T9) and swelling, shrinkage, twisting of the mycelium at concentrations from 20 ppm (T4) to 200 ppm (T9). The present study showed an encouraging results of the AgNPs against E. turcicum under in vitro conditions and emerged as effective substitute for the chemical control against northern corn leaf blight of maize in the world.