Application of liquid and solid organic fertilizers for ameliorating Cowpea aphid-borne mosaic virus disease in cowpea

Abstract

Cowpea (Vigna unguiculata L. Walp) is a major source of dietary protein in most African traditional households and also helps to replenish soil fertility. In spite of its vital role in reducing malnutrition, cowpea production is threatened by a wide range of virus diseases. This study was conducted to determine the effectiveness of liquid and solid organic fertilizers in the management of Cowpea aphid-borne mosaic virus (CABMV). The experiment was laid out in a completely randomised design with five replications. The seeds of virus-susceptible cowpea variety ‘Ife Brown’ were sown in plastic pots containing heat-sterilized soil. Treatments evaluated were uninfected non-fertilized, virus-infected + liquid organic fertilizer, virus-infected + solid organic fertilizer, and unfertilized virus-infected. Seedlings were infected with CABMV inoculum at 10 days after sowing. Disease incidence and severity, growth and seed weight were recorded. At 5 weeks after sowing, uninfected non-fertilized plants were consistently symptomless. Conversely, 100% disease incidence was encountered in unfertilized virus-infected plants. Significantly lower disease incidence (40.5%) was found in the virus-infected plants treated with liquid organic fertilizer than virus-infected plants treated with solid organic fertilizer (67.5%). Disease severity varied significantly between 1 and 5, in an increasing severity. A mean severity score of 2.3 was observed in the virus-infected plants treated with liquid organic fertilizer, which was significantly lower than a score of 3 observed in the virus-infected plants treated with solid organic fertilizer. Virus-infected plants treated with liquid organic fertilizer exhibited the highest seed weight (5.1 g), which was significantly higher than 3.2 g observed in the virus-infected plants treated with solid organic fertilizer. Unfertilized virus-infected plants had 2.2 g seed weight while the lowest came from unfertilized virus-infected (0.9 g). Therefore, application of liquid and solid organic fertilizers is recommended to suppress symptom expression and yield losses in cowpea fields that are prone to CABMV infection.