Mycoparasites cause heavy losses in commercial mushroom farms worldwide. The negative impact of fungal diseases such as dry bubble (Lecanicillium fungicola), cobweb (Cladobotryum spp.), wet bubble (Mycogone perniciosa), and green mold (Trichoderma spp.) constrains yield and harvest quality while reducing the cropping surface or damaging basidiomes. Currently, in order to fight fungal diseases, preventive measurements consist of applying intensive cleaning during cropping and by the end of the crop cycle, together with the application of selective active substances with proved fungicidal action. Notwithstanding the foregoing, the redundant application of the same fungicides has been conducted to the occurrence of resistant strains, hence, reviewing reported evidence of resistance occurrence and introducing unconventional treatments is worthy to pave the way towards the design of integrated disease management (IDM) programs. This work reviews aspects concerning chemical control, reduced sensitivity to fungicides, and additional control methods, including genomic resources for data mining, to cope with mycoparasites in the mushroom industry.

In 2010, symptoms of cobweb were observed on cultivated king oyster mushroom (Pleurotus eryngii) in Castilla-La Mancha (Spain) affecting 16% of the blocks of substrate cultivated. Cobweb appeared at the end of the crop cycle, first as small, white patches on the casing soil, subsequently spreading to the nearest king oyster mushroom by means of a fine gray-white mycelium, and eventually sporulating to produce masses of dry spores. The mycelium can quickly cover pinheads, stalks, pileus, and gills, eventually resulting in decomposition of the entire fruit body. Infected tissues of P. eryngii were plated onto potato dextrose agar (PDA) and the parasitic fungus was isolated. Fungal colonies consisted of abundant and cottony aerial mycelium spreading rapidly on PDA and red pigment spreading in the agar. Conidiogenous cells were 24 to 35 μm long, 3.5 to 5 μm wide basally, and tapered slightly to the tip. Conidia were cylindrical to narrowly ellipsoidal, 17 to 25 (-28) × 8 to 10 μm, and zero to three septate. Total DNA was extracted and the internal transcribed spacer (ITS) region of rDNA was amplified for one isolate using ITS1F/ITS4 primers (1,3). The amplicon was sequenced (GenBank Accession No. JF505112). BLAST analysis showed 100% similarity of the obtained ITS sequence with two sequences of Cladobotryum mycophilum (teleomorph Hypomyces odoratus) (GenBank Accession Nos. Y17096 and Y17095) (2). Pathogenicity tests were performed using 24 blocks containing sterilized, spawned, and incubated P. eryngii substrate (3.6 kg, 352 cm² in area). The blocks were placed in a mushroom-growing room and cased with a 40-mm layer of a casing soil (0.7 liter block^–1) made with mineral soil + Sphagnum peat 4:1 (vol/vol). Five days after casing, a conidial suspension (7 × 10³ conidia ml^–1) of one isolate of C. mycophilum was sprayed (5 ml per block) onto the surface of the casing layer at a rate of 10⁶ conidia m^–2. Twenty-two blocks were sprayed with sterile distilled water as a control. A temperature of 17 to 18°C and 85 to 90% relative humidity were maintained throughout cropping. The first cobweb symptoms developed 23 days after inoculation and C. mycophilum was consistently reisolated from nine (37.5%) of the inoculated blocks. Noninoculated blocks remained healthy. In a second test, conidial suspensions (3.4 × 10⁵ conidia ml^–1) of one isolate of C. mycophilum were inoculated onto 20 P. eryngii fruit bodies. Ten fruit bodies were inoculated externally while the other 10 fruit bodies were cut in half and inoculated internally with 50 μl of conidial suspension per fruit body. Sterilized distilled water was used as a control. All fruit bodies were then incubated at 22°C in a moist chamber. Assays were conducted twice and the results were recorded after 7 days. C. mycophilum grew on 85% of the internally inoculated fruit bodies and on 40% of those inoculated superficially, while the control mushrooms remained symptomless. To our knowledge, this is the first report of C. mycophilum causing cobweb in king oyster mushroom in Spain. This finding will have a potentially significant impact on button mushroom farms where cobweb is one of the most common diseases. References: (1) M. Gardes and T. D. Bruns. Mol. Ecol. 2:113, 1993. (2) G. J. McKay et al. Appl. Environ. Microbiol. 65:606, 1999. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

The objective of this work was to evaluate the efficacy of two nematodes, Steinernema feltiae and S. carpocapsae, to control mushroom flies and to evaluate the effect of these treatments on Agaricus bisporus production. Two mushroom cultivation trials were carried out in controlled conditions, in substrate previously infested with the diptera Megaselia halterata and Lycoriella auripila, with two treatments: 10⁶ infective juveniles (IJ) per square meter of S. feltiae and 0.5x10⁶ IJ m^-2 S. feltiae + 0.5x10⁶ IJ m^-2 S. carpocapsae. Another experiment was carried out using the same treatments to evaluate the possible nematode effect on mushroom yield. The number of adults emerging from the substrate was evaluated for each fly species. No decrease in the population of M. halterata was detected with nematode application, whereas the number of L. auripila was reduced in both treatments, particularly in the individual treatment with S. feltiae. The application of entomopathogenic nematodes has no adverse effect on mushroom production.

Lentinula edodes, known as shiitake, is the main cultivated edible mushroom worldwide, representing about 22% of the world’s output, with China being the major producer. In 2017 symptoms of cobweb were observed on cultivated shiitake mushrooms in Castilla-La Mancha (Spain), affecting more than 30% of the blocks of pasteurized substrate. Cobweb appeared at the end of the crop cycle as circular white patches over the surface of the blocks of substrate and fruitbodies. The fine grey-white mycelium rapidly covered pinheads, stalks, pileus and gills, eventually resulting in the decomposition of the entire fruitbody. The mycelium can colonize the surface of the substrate completely and may turn reddish brown. To isolate the parasitic fungus, infected tissues of L. edodes were plated onto potato dextrose agar (PDA). Fungal colonies consisted of white, cottony, aerial mycelium that spread rapidly on the PDA, changing from white to yellow and finally, pink, as the red pigment spread into the agar. The conidiogenou...