Project Code: BPR15-041
Project lead
Odile Carisse - Agriculture and Agri-Food Canada
Objectives
To develop an integrated management program incorporating the biopesticide Botector® and other best practices for the control of Botrytis grey mould in greenhouse tomato
Botrytis grey mould, caused by the fungal pathogen Botrytis cinerea, is a devastating disease of tomato in greenhouses across Canada. The biopesticide Botector® (Aureobasidium pullulans) was identified by growers as a priority solution for the control of Botrytis grey mould on multiple crops in 2014. Through regulatory support provided by the Pesticide Risk Reduction team of Agriculture and Agri-Food Canada's Pest Management Centre, in 2020 Botector® was finally registered in Canada for use on a broad range of field and greenhouse grown vegetable, berry, herbs and ornamental crops.
This 2-year project aimed to develop an integrated approach involving optimal timing of Botector® applications in combination with other cultural practices for the control of Botrytis grey mould in greenhouse tomato.
Approach
Three integrated pest management (IPM) strategies were evaluated in artificially inoculated greenhouse tomato chambers, and only one of these was validated in commercial greenhouse under natural infection conditions. Each strategy involved cultural practices commonly used by growers including de-leafing (removal of old bottom leaves) and cleaning up removed leaves from trial chambers. In the control chambers, only the common cultural practices were applied as in each of other strategies, without using any conventional fungicides or biopesticides. Flower and stem-wound infections were monitored weekly to assess the efficacy of each strategy. Spore samplers were installed to detect concentrations of B. cinerea airborne spores concentration in the chambers.
A. Integrated Biological Management (IBM) strategy included two scenarios:
- the biopesticide Botector® was applied once at a low air humidity as a preventive treatment on stem wounds after de-leafing operations; and
- Botector® applications continued as long as the concentration of B. cinerea airborne spores was below 100 conidia per metre cubed (conidia/m3) or when 1-2 stem wounds were infected after de-leafing of plants. On average, six Botector® applications were carried out under the A strategy trials.
B. Integrated management (IM) strategy: Botector® was applied on stem wounds when airborne inoculum levels were between 10 and 25 conidia/m3, and also Botector® was applied on foliar, flower and stem wounds when grey mold disease symptoms were detected and airborne inoculum levels were between 25 and 100 conidia/m3. Conventional fungicides (fenhexamide, pyriméthanil and fluopyram) were applied in this strategy when symptoms were detected and the airborne inoculum level was above 100 conidia/m3. On average, 4.3 Botector® applications and 3.3 conventional fungicide applications were carried out during the B strategy trials.
C. Optimised Chemical Management (OCM) strategy included applications of conventional fungicides (fenhexamide, pyriméthanil and fluopyram) along with the indicated cultural practices. The fungicide application started when the inoculum was at a level above 25 conidia/m3 or when there were 1-2 stem wounds infected or flower blight was present. On average, 5.3 conventional fungicide applications were carried out and no Botector® was applied.
Among the three approaches tested, only the IBM (A) strategy was validated in a commercial greenhouse under natural infection conditions. Comparison in this case, was made with another commercial greenhouse adopting standard grower's practices, including removal of diseased flowers or fruits and lowering air humidity when grey mould is observed. Two spore samplers were installed in each of the above greenhouses to detect concentrations of B. cinerea spores. Flower and stem-wound infections were assessed weekly for efficacy evaluations.
Results
Both the IBM (A) and IM (B) strategies, which included the Botector® biopesticide, performed similarly providing significant control of the disease, reducing flower infections by 86 and 91% and stem infections by 96 and 97%. Concentration of Botrytis airborne inoculum in IBM and IM chambers was also reduced by 61 and 66%, respectively, compared to control chambers. The OCM (C) strategy also significantly reduced flower infection (by 59%), stem wound infection (by 72%), and airborne inoculum concentration (by 30%) compared to control chambers, but performance was inferior to the IBM and IM strategies.
In the commercial greenhouse the IBM (A) strategy significantly reduced flower infection (by 72%) and stem wound infection (by 73%), as well as spore concentration by 30% compared with the standard practices.
Conclusions
Results of this project indicate that the biopesticide Botector® can be considered as an important tool as part of an integrated management of Botrytis grey mold in greenhouse tomato. When incorporated in a strategy that aims at first reducing disease pressure and secondly optimizing the application conditions, Botector® can provide commercially viable control with acceptable number of applications. The strategy that included a combination of Botector® and conventional fungicides (IM) provided an excellent disease control efficacy, and better than the optimised chemical only based strategy (OCM). The key outcome for the IBM strategy was that preventive application of Botector® on stem wounds after the de-leafing operations and repeated when reached spore concentration thresholds, along with decreasing greenhouse air humidity and practicing good sanitation by removing all foliar residues from greenhouse can provide a far superior disease management compared to a chemical based control strategy. While optimizing management of Botrytis grey mold, the system that incorporates the use of biopesticide and chemical products was shown to lead to a significant reduction of conventional fungicides application, reduction in pathogen inoculum pressure, and also lower the risk of pathogen developing resistance to available conventional fungicides. All these benefits enable growers to adopt sustainable production practices and enhance their competitiveness in domestic and international markets.