Rhizochrysis

Rhizochrysis is a genus of golden algae (Chrysophyceae) that can negatively affect plant health, particularly in hydroponic systems and high-moisture greenhouse environments. While these organisms are not traditional fungal pathogens, their proliferation on root surfaces leads to significant physiological stress and growth impairment in agricultural crops.

The causative agent belongs to the class of golden algae, which thrive in moist environments enriched with nutrients. Unlike fungal infections that penetrate tissues, this organism primarily forms dense, mucilaginous films on the surface of roots, physically inhibiting nutrient uptake and gaseous exchange between the plant and its growing medium.

Crop susceptibility is highest among greenhouse vegetables such as tomatoes, cucumbers, and various hydroponic leafy greens. Seedlings in nurseries are also at risk, especially when growing conditions include constant high humidity and exposure to light, which triggers the photosynthetic activity of the algae on exposed root zones.

Symptoms of an infestation typically manifest as a discoloration of the root system. The roots may appear yellowish, brownish, or develop a slimy coating that feels slick to the touch. Infected plants exhibit visible signs of nutrient deficiency, stunted growth, reduced leaf turgor, and overall chlorosis, despite maintaining a proper irrigation and fertilizer regime.

Effective management and protection strategies rely on physical and chemical intervention:

• Blocking light penetration to root zones and hydroponic reservoirs to prevent algal photosynthesis.
• Regular disinfection of irrigation systems and hydroponic equipment with algaecides.
• Improving aeration within the root zone to prevent stagnant water.
• Monitoring the nutrient solution for signs of contamination and adjusting levels of mineral additives.