Seed health status of mustard seeds as influenced by foliar sprays against powdery mildew disease.
A study was conducted in Karnataka, India, in 2005 to investigate the effects of powdery mildew (caused by Erysiphe cruciferarum) severity on the seed health status of Indian mustard in respect of seed abnormality, seed germinability and seedling vigour as influenced by foliar sprays of fungicides, phytoextracts and one biological control agent (Trichoderma viride at 3.00%) against powdery mildew under field conditions. The treatments comprised extracts (each at 5.00%) of leaves of neem (Azadirachta indica), Eucalyptus globulus, Nerium indicum [N. oleander] and karanj (Pongamia pinnata), and bulbs of onion; hexaconazole (Contaf 5 EC) at 0.05%; Wettable sulfur (Sulfex 80 WP) at 0.20%; tebuconazole (Folicur 25 EC) at 0.05%; tridemorph (Calixin 48 EC) at 0.04%; difenconazole (Score 25 EC) at 0.05%. The foliar sprays were performed thrice at an interval of 12 days commencing from the appearance of powdery mildew in the experimental area. The results revealed significant differences in number of abnormal seeds observed in various treatments. All the fungicides reduced the abnormal seeds significantly over all other treatments. T. viride also reduced such seeds significantly over the phytoextracts and the control. Significantly the maximum abnormal seeds, i.e. 34.33 per 400 seeds were detected in the control. With the phytoextracts such seeds ranged from 30 to 33, whereas 23-33 abnormal seeds were observed in T. viride. The least number of abnormal seeds (18.00-19.66) were recorded in the fungicidal treatments. Thus, the fungicides and T. viride helped reducing abnormal seeds. The seeds harvested from the plots sprayed with the fungicides recorded the best seed germination (90.50-92.75%). The minimum germination was in karanj (84.75%), which was at par with the control and remaining phytoextracts, including T. viride (87.75%). The fungicides and T. viride produced significantly higher mean seedling length compared to the control and phytoextracts. The maximum length was 12.86 cm in hexaconazole, whereas the minimum was 11.99 cm in neem leaf extract. The seedling vigour index was higher with the fungicides ranging from 1149.6 to 1192.8 compared to 1022.1 to 1075.0 in the phytoextracts and control. T. viride revealed 1097.8 vigour index and stood next to the fungicides.