Preparation Method of Compost Tea Affects Its Suppression of Grey Mould ( Botrytis cinerea ) of Tomato Plants

ABSTRACT

Botrytis cinerea , causing grey mould disease, is a serious pre‐ and postharvest fungal phytopathogen. Conventional methods for disease control rely on chemical fungicides, which have associated health and environmental effects. Disease suppressive compost teas (CTs) provide a promising alternative. In this study, CTs prepared from sheep manure (SHE), bovine manure (BOV) and shrimp residue (SHR) composts at two preparation dilutions (1:5 and 1:10 compost:water) were tested for their suppressive effect against tomato grey mould. Results showed all CTs reduced disease severity for up to 7 weeks, except SHE 1:5 and BOV 1:10. SHR teas, regardless of dilution, reduced disease severity and improved plant growth. SHE 1:10 was equally as effective at reducing disease severity as the SHR teas. SHE 1:5 impaired plant growth by 12% whereas SHE 1:10 had no effect on plant growth. BOV 1:10 improved plant growth by 29% but BOV 1:5 had no effect on plant growth. Metagenomic analysis revealed distinct differences in the bacterial and fungal communities of suppressive CTs, with the most efficient CTs distinctly clustering apart from the less effective teas. Genus‐level analysis revealed specific antagonistic microorganisms that may be responsible for the differences in suppressive activity observed, notably Trichoderma in combination with Arthrobacter and Pseudomonas .