Frosty pod rot, caused by Moniliophthora roreri, is the most damaging disease of cacao in Latin America and, to better comprehend its epidemiology, we must understand its dissemination and proliferation. However, we do not know how M. roreri spores loads fluctuate in time and space due to the lack of a reliable technique to quantify M. roreri spores in the fields. Therefore, we developed a method that relies on spore traps and qPCR to detect and quantify M. roreri spore loads. This study demonstrated that the qPCR protocol can detect down to 0.025 ng of M. roreri DNA and quantify between 0.006 ng and 60 ng. Moreover, it demonstrated that qPCR protocol can detect and quantify DNA extracted from spore suspension and spore traps containing at least 2.9 × 104 M. roreri spores. However, the variability of the estimates for spore samples was high. Finally, we described a spore-trap device designed to carry spore traps in the field. The qPCR protocol and spore-trap device here developed will help in the understanding of the M. roreri dissemination patterns since they can be used to assess the environmental loads of M. roreri spore in cacao fields.

Frosty pod rot, caused by Moniliophthora roreri, is the most damaging disease of cacao in Latin America. However, to better comprehend its epidemiology, we must understand its dissemination and proliferation. Still, we ignore how loads of M. roreri spores fluctuate across growing seasons since we lack a reliable technique to quantify M. roreri spores in the fields. Therefore, we developed a method that uses a spore trap to capture M. roreri spores and qPCR to quantify them. This study demonstrated that this technique could quantify 3.9 x104 M. roreri spores with a 95 % confidence level. However, it could not differentiate between M. roreri and its close relative, M. perniciosa. Despite this limitation, we could detect and quantify Moniliophthora spores from environmental samples taken from a cacao field. This technique can help the phytopathologist address studies more accurately in disseminating cacao pathogens.