Association of Granary Mites and Seed-Borne Fungi in Stored Grain and in Outdoor and Indoor Habitats1

Abstract

One hundred mite-infested samples of wheat, oats, and barley from grain spill adjacent to granaries, granary floors, and grain bulks in various parts of Canada were collected during 1961–65. The faunal and floral populations were identified to specific or generic level; their frequency on each cereal, in each habitat, and the relative frequency of association between individual species of mites and microorganisms were recorded. Thirty-six genera (more than 46 species) of mites, 27 genera (more than 38 species) of fungi, and 1 genus of Actinomycetes (at least 3 species) were identified. The commonest mites, i.e., those present in 30%–20% of all samples, were, in descending frequency: Glycyphagus destructor (Schrank), Acarus ferris (Oudemans) A. siro L., Cheyletus eruditus (Schrank), Haemolaelaps casalis (Berlese), and Tydeus interruptus Thor. Of the economically important mite species A. ferris was common on all cereals, both in outdoor and indoor bulk habitats; but A. siro, which was more prevalent on wheat and barley than on oats, predominated in the indoor bulk, and was not found in outdoor samples. The commonest microorganisms, i.e., those present in 94%–35% of all samples, were, in descending frequency: Streptomyces spp., Alternaria tennis sensu Wiltshire, Penicillium spp., Hormodendrum cladosporioides (Fresenius) Saccardo, Trichothecium roseum Link, and Aspergillus versicolor (Vuillemin) Tiraboschi. Of the economically important microorganisms: Penicillium spp., which were more prevalent on wheat and barley than on oats, occurred in all habitats; H. cladosporioides, which was commonest on oats, occurred in all habitats; and A. versicolor, which was common on all cereals, occurred only in grain bulks indoors. Acarus ferris and A. siro were frequently associated with the fungi Alternaria tenuis, H. cladosporioides, Nigrospora sphaerica (Saccardo) Mason, and T. roseum on which they also thrive in the laboratory. G. destructor was most frequently associated with Penicillium spp. and A. tenuis, which also support the mite population in the laboratory. Probable sources and modes of infestation of stored grain by mites and fungi are discussed.