Plant acholeplasmosis

The causative agents of this disease belong to the Acholeplasmataceae family, a group of wall-less prokaryotes classified under mollicutes. Unlike other similar pathogens, acholeplasmas can be cultured on cell-free artificial media, which is a key diagnostic feature. Once inside the plant, these pathogens inhabit the sieve tubes (phloem), disrupting the translocation of nutrients and causing severe physiological dysfunction.

Acholeplasmosis affects a diverse array of agricultural and horticultural crops. Major hosts include vegetables such as tomatoes and potatoes, various berry crops like strawberries, and several ornamental plants. The systemic nature of the infection means that the pathogen spreads throughout the entire vascular system of the host, leading to a long-term decline in plant vigor and productivity.

Symptoms are often manifested as yellowing or reddening of leaves, stunting, and an abnormal proliferation of auxiliary buds, known as the "witches' broom" effect. Affected plants may show reduced fruit set, fruit malformation, or poor development of reproductive organs. Because these symptoms are often mistaken for viral or nutritional deficiencies, accurate identification requires laboratory confirmation.

Transmission occurs primarily through insect vectors, specifically leafhoppers and planthoppers, which acquire the pathogen while feeding on infected sap. The spread of the disease is highly dependent on the population dynamics of these vectors, which thrive in warm, dry weather conditions. Once introduced into a field, the disease can spread rapidly, especially if weed hosts near the crop are not managed.

Management of acholeplasmosis is challenging because there is no chemical cure for infected plants. Protection relies on integrated pest management (IPM) practices:

• Rigorous control of insect vectors using targeted insecticide applications.
• Elimination of weeds that serve as alternative hosts for both the pathogen and its vectors.
• The use of certified pathogen-free propagating material.
• Implementing buffer zones and physical barriers such as insect-proof nets in greenhouses.
• Regular roguing of infected plants to reduce the local inoculum pressure.