Efficacy of fungicides, plant resistance activators and biological control agents against guava wilt disease caused by Nalanthamala psidii

Abstract

Guava wilt disease (GWD) caused by the fungus Nalanthamala psidii remains a major constraint to guava production in South Africa and South-east Asia. In the current study, chemical and biological products as well as plant resistance activators were evaluated for control of GWD in shadehouse and glasshouse trials. In all trials, one-year-old ‘TS-G2’ guava plants were used. Plants were inoculated with a macerated culture suspension of a mixture of three isolates of N. psidii after artificial wounding of the roots. Products were applied as a soil drench or as a full cover spray. In Trial 1 plants were evaluated according to a disease severity scale. In Trials 2 and 3 data were recorded as number of dead plants at the termination of the trial. None of the chemical treatments caused a significant suppression of the disease. The best control was achieved with the combination of rhizobacterial strains Bacillus cereus S7 and Paenibacillus alvei T29 resulting in 53.4% and 50% disease control in Trials 2 and 3, respectively. This treatment also seems to have a plant growth-enhancing effect apart from disease suppression. This is to our knowledge the first report of control of GWD by means of bacterial antagonists.