We report a biosensor that combines the construction of a three-dimensional nanocomposite with electrochemical methods for the detection of viruses in plants. This is the first report, where carbon nanotubes are used as a conductive frame to anchor highly electrolytic agglomerates of copper nanoparticles to detect agroviruses. Morphological analysis of nanocomposite revealed the presence of carbon nano tubes having a diameter of 50-100 nm with copper nanoparticles of 20-100 nm, attached in the form of bunches. This material was applied to assess the infection caused by geminiviruses which are a major threat to the cotton plants in Asian and African countries. The hybridization events were studied by monitoring differential pulse voltammetry signals using methylene blue as a redox indicator. In the presence of target DNA, sensor signals decreased from 7 x 10(-4) to 1 x 10(-4) Ampere. The probe exhibited 97.14% selectivity and the detection limit was found to be 0.01 ng UL-1. The developed biosensor is stable for at least four weeks, losing only 4.3% of the initial signal value. This sensor was able to detect the presence of viruses in sap extracted from cotton leaves, thus providing a promising platform to detect a range of other crops infecting viruses. (C) 2017 Elsevier B.V. All rights reserved.