Sustainable management approaches for fungal pathogens on vegetable crops

Sustainable methods for the management of greenhouse pathogens such as Fusarium on tomato and powdery mildew on cucumber were investigated. A systematic review of calcium nutrition and its impact on diseases was performed. Calcium has been shown to impact disease development on over 40 crops and 35 pathogens. Direct inhibition of the pathogen, increase in cell wall strength and induced resistance are all modes of action that have been reported for calcium. Formulations of karanja oil (Millettia pinnata extract) were tested for their efficacy at reducing spore germination and mycelial growth of Fusarium oxysporum and in reducing disease development on greenhouse grown cucumber plants. Spore germination of F. oxysporum was inhibited by 100 % after 12 hr exposure when added to potato dextrose broth at a concentration of 0.1 %. The same concentration inhibited mycelial growth by 96 % after 7 days. Inconsistent Fusarium infection and symptom development resulted in no significant disease reduction by karanja oil. On cucumber plants, foliar sprays of the karanja formulations reduced the severity of powdery mildew infection by 73.6 %. On squash plants, foliar sprays increased plant weight by 80%. These results show the potential of karanja oil for suppressing pathogen growth in vitro and in vivo.