If your wheat grass catches the fungus, the following might be the reasons.

1. Lack of proper watering or over watering.
2. Lack of proper lighting.
3. Lack of good air circulation.
   

• For proper watering, ensure your trays have drainage holes at the bottom for bottom watering. Water only when the soil is dry; avoid making it soggy by over watering.
• Please keep them in indirect bright sunlight or under led grow lights or a table lamp will also work fine.
• Please keep them in a well-ventilated area with good air circulation.
  
• Do not over soak or sprout the seeds before sowing (soak only for maximum 12 hours & then later sprout them for 12 hours).
  
• High humidity in the weather may also cause fungus.
  You can discard this wheat grass with fungus and start with a new batch.

You can watch our YouTube video on How to grow Wheatgrass at home?