Bacillus subtilis based-formulation for the control of postbloom fruit drop of citrus.
Postbloom fruit drop (PFD) caused by Colletotrichum acutatum affects flowers and causes early fruit drop in all commercial varieties of citrus. Biological control with the isolate ACB-69 of Bacillus subtilis has been considered as a potential method for controlling this disease. This study aimed to develop and optimize a B. subtilis based-formulation with a potential for large-scale applications and evaluate its effect on C. acutatum in vitro and in vivo. Bacillus subtilis based-formulations were developed using different carrier materials, and their ability to control PFD was evaluated. The results of the assays led to the selection of the B. subtilis based-formulation with talc + urea (0.02 %) and talc + ammonium molybdate (1 mM), which inhibited mycelial growth and germination of C. acutatum. Studies with detached citrus flowers showed that the formulations were effective in controlling the pathogen. In field conditions, talc + urea (0.02 %) provided 73 % asymptomatic citrus flowers and 56 % of the average number of effective fruit (ANEF), equating with fungicide treatment. On the contrary, non-treated trees had 8.8 % of asymptomatic citrus flowers and 0.83 % ANEF. The results suggest that B. subtilis based-formulations with talc as the carrier supplemented with a nitrogen source had a high potential for PFD control.
Agroecology and Rural Development Program, Postgraduate School, Universidade Federal de São Carlos, Araras, SP, CEP 13600-970, Brazil.
Mariana Nadjara
MN
Klein
Agroecology and Rural Development Program, Postgraduate School, Universidade Federal de São Carlos, Araras, SP, CEP 13600-970, Brazil.
Aline Caroline
AC
da Silva
Laboratory of Plant Pathology and Biological Control, Centro de Citricultura "Sylvio Moreira"/IAC, Cordeirópolis, SP, CEP 13490-970, Brazil. katia@centrodecitricultura.br.
Katia Cristina
KC
Kupper
D001412:Bacillus subtilis / Q000502:physiology*; D002957:Citrus / Q000254:growth & development* / Q000382:microbiology; D020231:Colletotrichum / Q000187:drug effects* / Q000472:pathogenicity; D035264:Flowers / Q000254:growth & development / Q000382:microbiology; D005659:Fungicides, Industrial / Q000378:metabolism / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D008982:Molybdenum / Q000378:metabolism / Q000494:pharmacology; D010935:Plant Diseases / Q000517:prevention & control*; D013627:Talc / Q000378:metabolism / Q000494:pharmacology; D014508:Urea / Q000378:metabolism / Q000494:pharmacology
D005659:Fungicides, Industrial; D013627:Talc; D008982:Molybdenum; D014508:Urea; C022175:ammonium molybdate
Additives; Biological control; Bioproducts; Colletotrichum acutatum; Survival