The Role of Water Content in the Casing Layer for Mushroom Crop Production and the Occurrence of Fungal Diseases

Mushroom cultivation requires effective control of environmental cues to obtain the best yield and high quality. The impact of water content in the casing layer on mushroom yield and the incidence of two of the most important diseases in the mushroom growing farms, dry bubble and cobweb diseases, was evaluated. Different initial water content in the casing and two alternative irrigation programs applied (light or moderate irrigation) were the agronomic parameters under study during five separate button mushroom crop trials. Higher initial humidity content in the casing layer reported a larger yield, with a fewer number of basidiomes but heavier, while no correlation to the dry matter content or the colour of the basidiomes was noted. The incidence of dry bubble disease was not conditioned by the water content of the casing layer, at the high moisture levels established in the study. In the case of Cladobotryum mycophilum, the lower moisture level of the casing layer reported more incidence of cobweb disease, and subsequently harmful yield losses. According to the results obtained, the right management of the moisture level in the casing materials could promote crop yield and preclude the significant impact of dry bubble and cobweb diseases.

Efficacy of Liquid Soap and Alcohol-Based Hand Sanitisers in Eradicating Viable Conidia of the Mushroom Pathogen Lecanicillium fungicola on Contaminated Hands

Lecanicillium fungicola causes dry bubble disease of the white button mushroom and produces masses of sticky conidia. Humans are an important vector in the spread of this disease in mushroom farms. Three hand cleaning treatments (tap water, liquid soap and alcohol-based hand sanitisers (ABHSs)) were evaluated for their effectiveness at eliminating conidia of L. fungicola from a contaminated index finger. The hand sanitisers were highly efficacious in reducing the number of viable L. fungicola conidia on contaminated fingertips, although some variability was encountered. The tap water and liquid soap treatments had little effect. An in vitro test confirmed that the log10 reduction in viable conidia after 1 min exposure to the different treatments was ≤0.15 for tap water and soap and >4.5 for the ABHSs, which is similar to what is achieved in the medical care field for many bacteria and viruses. Thus, regular use of ABHSs by staff on mushroom farms may help to reduce the incidence of dry bubble disease. Their use could also be beneficial in other areas of intensive horticulture or agriculture where human hands are known to transmit plant pathogens to uninfected plants.

Control of Fungal Diseases in Mushroom Crops while Dealing with Fungicide Resistance: A Review

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.

Genome Sequence of Lecanicillium fungicola 150-1, the Causal Agent of Dry Bubble Disease

The fungus Lecanicillium fungicola causes dry bubble disease in the white button mushroom Agaricus bisporus. Control strategies are limited, as both the host and pathogen are fungi, and there is limited understanding of the interactions in this pathosystem.

Essential oils in the control of dry bubble disease in white button mushroom

ABSTRACT: Lecanicillium fungicola, which causes Dry bubble disease, induces infections and inflicts major losses in champignon production. The control can be managed through measures of hygiene and use of fungicides; however, in Brazil there are no registered products. This study aimed to estimate the influence of various essential oils extracted from Melissa officinalis, Thymus vulgaris, Origanum vulgare, Eucalyptus globulus, Cinnamomum zeylanicum and Syzygium aromaticum on the in vitro development and their uses. Therefore, analysis was performed of the L. fungicola isolates in vitro and the best oils were tested in vivo. Besides, the Agaricus bisporus - L. fungicola interaction was confirmed by scanning electron microscopy (SEM). Cinnamon and clove oils in concentrations of 0.4% and thyme oil of 0.8% were identified as good growth inhibitors of the pathogenic mycelium. Effective inhibition of the conidial germination was seen in all concentrations by cinnamon oil, and by clove and thyme oils only at 0.4% and 0.8%, respectively. When the essential oils were applied post-infestation in the in vivo experiments the incidence of the disease in the mushrooms was much lower. From the SEM it was clear that 19 hours after the inoculation of A. bisporus with L. fungicola, the spores had already completely germinated, revealing the presence of the infection. Therefore, the findings of this study indicated that the oil extracts of cinnamon, clove and thyme are potential and efficient alternatives in the control of dry bubble disease.

Evaluation of some plant extracts in management of dry bubble (Verticillium fungicola) disease of white button mushroom [Agaricus bisporus (Lange) Imbach]

The study was undertaken to determine antifungal potentials of some plant extracts against dry bubble (Verticillium fungicola) disease of white button mushroom (Agaricus bisporus). Twelve botanicals namely, Allium cepa, A. sativum, Saraca asoca, Aloe vera, Azadirachta indica, Lantana camara, Ocimum sanctum, Solanum lycopersicum (Lycopersicon esculentum), Tagetes erecta, Psidium guajava, Catharanthus roseus and Aparagus racemosus were evaluated in-vitro and in-vivo for their efficacy against both A. bisporus and V. fungicola, causing dry bubble disease of mushroom. The efficacy of botanicals was examined by poison food technique in in-vitro. The percent inhibition produced by botanicals against V. Fungicola recorded in-vitro was; A. cepa (25.87%), A. sativum (24.70%), S. asoca (12.35%), A. vera (22.35%), A. indica (35.11%), L. camara (28.48%), O. sanctum (20.59%), S. lycopersicum (20.34%), T. erecta (14.11%), P. guajava (15.11%), C. roseus (18.11%) and A. racemosus (13.52%). Among these plant extracts, A. indica was found best treatment followed by L. Camara and A. Cepa. Plant extracts showing maximum efficacy against V. fungicola and minimum inhibition against mushroom were further evaluated against V. fungicola infection in mushroom crop room (in-vivo test). In in-vivo test, the polybags which receive A. indica show maximum mean increase in yield (43.46%) over control and exhibited minimum mean disease incidence (27.7%).

The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels

This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these “dry” bubbles, contact line forces and a possible capillary pressure gradient induced by pinning act on the bubbles and resist motion. Without sufficient driving force (e.g., external pressure), a dry bubble is brought to stagnation. For the first time, a bipartite theoretical model that estimates the required pressure difference across the length of stagnant bubbles with concave and convex back interfaces to overcome the contact line forces and stimulate motion is proposed. To validate our theory, the pressure required to move a single dry bubble in square microchannels exhibiting contact angle hysteresis has been measured. The working fluid was de-ionized water. The experiments have been conducted on coated glass channels with different surface hydrophilicities that resulted in concave and convex back interfaces for the bubbles. The experimental results were in agreement with the model's predictions for square channels. The predictions of the concave and convex back models were within 19% and 27% of the experimental measurements, respectively.