Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2005
Publication Date: 8/8/2005
Citation: Horst, L., Locke, J.C., Krause, C.R., Mcmahon, R.W., Madden, L.V., Hoitink, H.A. 2005. Suppression of botrytis blight of begonia by trichoderma hamatum 382 in peat and compost-amended potting mixes. Plant Disease. 89:1195-1200. Interpretive Summary: Botrytis Blight of Begonia caused by Botrytis cinerea annually reduces grower profitability and the quality of bedding plants. The fungus, Trichoderma hamatum, Strain # 382 (T382) was incorporated into a standard greenhouse potting mix made with light sphagnum peat. Tests were performed and showed that T382 significantly reduced the severity of Botrytis Blight on Begonia when shoot dry weight and salability were quantified. T382 significantly improved Botrytis control when compared to foliar sprays of the conventional synthetic fungicide, chlorothalonil. In other tests, the addition of composted cow manure increased Begonia dry weight and quality (salability). All treatments were spaced to prevent cross-contamination during tests. We conclude that T382 inoculation of potting media suppressed Botrytis Blight though systemic action. The biocontrol agent, T382, could become an alternative to conventional fungicides by suppression of the disease.
Technical Abstract: Inoculation of a light Sphagnum peat potting mix with Trichoderma hamatum 382 (T382) significantly (P= 0.05) reduced the severity of Botrytis blight of Begonia caused by Botrytis cinerea. This treatment increased shoot dry weight and also improved the salability of flowering Begonia plants. Over four experiments, the degree of control provided by T382 was significantly (P=0.05) better than that provided by weekly topical sprays with chlorothalonil. Amendment of the peat mix with composted cow manure (5%; v/v) also significantly (P=0.05) decreased the severity of the disease. Shoot dry weight was increased whereas plant salability was improved by amendment with compost. Topical sprays with chlorothalonil or inoculation with T382 did not consistently change disease severity relative to the nontreated compost-amended mix. Shoot dry weight and salability of flowering plants in the compost mix also were not affected consistently by either treatment. Spatial separation between the biocontrol agent T382 and the pathogen was maintained on the host plant in each of the four experiments. It was concluded, therefore, that the decrease in disease severity and improvement in plant salability and dry weight provided by inoculation of the peat mix with T382 was due to systemic activity induced in Begonia by the biocontrol agent.