Phytophthora root rot

The causative agent of the disease is the oomycete Phytophthora cryptogea, a soil-borne pathogen. It is a highly destructive organism capable of causing systemic root and crown rot, which often leads to total plant collapse. This pathogen is particularly problematic in both greenhouse and nursery production environments.

The host range for Phytophthora cryptogea is extensive. It affects a wide array of vegetable crops, such as tomatoes, peppers, and cucumbers, as well as a significant number of ornamental plants, including various bulbs and flowers like gerberas and chrysanthemums, causing severe economic damage.

Infected plants typically show signs of wilting, stunted growth, and yellowing foliage. Upon closer inspection, the root system shows signs of decay, appearing brown and necrotic. The rot can eventually progress to the crown, resulting in a firm, reddish-brown discoloration of the stem tissue.

The pathogen thrives in conditions of high soil moisture and poor drainage. Since the zoospores of the fungus rely on water films to move and reach the roots, over-irrigation or waterlogged soil are the primary drivers of disease spread and establishment within a plant population.

Effective management requires an integrated approach. Prevention strategies include using pathogen-free planting media, ensuring excellent drainage, and avoiding the reuse of contaminated irrigation water. Chemical control, using systemic fungicides that target oomycetes, is often necessary when the disease is already present.