When buying an inoculant for mycorrhiza is the number of spores important?
Yes, the number of spores can be important, but more important is the degree of infectivity present in an inoculant. How effective an inoculant is depends on how rapid it can cause colonization of the root system. Spores tend to be the least infective of fungal parts in the genus Glomus (which comprise the majority of commercially available inoculants). Hyphal fragments are most infective, followed by mycorrhizal root fragments. All three infective components are referred to as propagules by INVAM (http://invam.caf.wvu.edu/otherinfo/articles/propagules.htm). Make sure that the species used in the inoculant are diverse and have been proven to be effective over wide ranges of plant species, pH, and soil types. (DIEHARD species are proven – see a +40 page reference list.) Consumers can be fooled by companies that claim high spore count but use weak, or ineffective spores, in the count that are easy to reproduce to achieve spore count specifications. Some spores too offer little potential
