Glomerella gossypii

The pathogen produces fruiting bodies known as acervuli within plant tissues. These structures release numerous conidia, which are responsible for the secondary spread of the disease during the growing season.

The fungus persists in infected seeds, crop debris, and on weed hosts within the Malvaceae family. Its ability to remain viable in soil and seed makes it a persistent challenge for cotton producers.

The infection process initiates when a conidium lands on a plant surface and germinates. It forms an appressorium, a specialized structure that generates physical force and enzymes to penetrate the host epidermis.

Laboratory diagnosis involves isolating the pathogen on culture media, where it typically develops an olive-gray mycelium and produces large quantities of characteristic spores under proper lighting and humidity conditions.

The primary host for this pathogen is the cotton plant (Gossypium spp.). The disease affects all aerial parts of the plant, from the seedling stage through to boll development.

Anthracnose results in seedling blight, leaf spotting, stem lesions, and boll rot. These symptoms severely impact both the density of the crop and the economic value of the harvested fiber.

Infected bolls open prematurely, and the lint within becomes discolored, weak, and matted. This degradation makes the fiber unsuitable for high-quality textile manufacturing and reduces yield weight significantly.

In regions with high rainfall during the flowering and boll-setting stages, losses can reach up to 50% of the total yield. Secondary infection of bolls is often the most economically damaging phase.

Seed transmission is a major concern, as infected seeds lead to poor germination rates and introduce the pathogen to new planting areas.

Primary inoculum is usually provided by infected seeds or contaminated crop residues in the soil. Infection often occurs shortly after planting, particularly if the soil remains cold and wet for extended periods.

During the summer, the disease cycle accelerates under warm, humid conditions. Rain splash and high winds are primary drivers for the dispersal of conidia from the lower foliage to the upper bolls.

The fungus thrives at temperatures ranging from +22°C to +28°C with high relative humidity. Under these conditions, the incubation period can be as short as a few days.

As bolls mature, they remain susceptible to late-season infections. If the bolls are damaged by insects or mechanical stress, the pathogen easily invades the internal tissues.

The pathogen enters a survival phase in the soil after harvest, overwintering on plant debris until the following growing season.

Seedling blight appears as reddish-brown lesions on the hypocotyl, causing the stem to collapse and the seedling to die before or shortly after emergence.

Leaf symptoms include circular brown spots with lighter centers and darker margins. Severe infections lead to extensive chlorosis and premature defoliation of the cotton plants.

Stem lesions manifest as sunken, necrotic areas that can girdle the stem, restricting the flow of water and nutrients and leading to plant wilting or death.

On bolls, the disease presents as dark, sunken spots that eventually cover with a pinkish or salmon-colored mass of spores under humid conditions.

• Seedling damping-off and death.
• Leaf spotting and premature leaf drop.
• Necrotic lesions on stems and branches.
• Pinkish spore masses on infected bolls.
• Poor quality, discolored lint.

The foundation of control is the use of high-quality, disease-free, and fungicide-treated seed. Seed treatments significantly reduce the incidence of primary infections during the seedling stage.

Crop rotation is essential for long-term management. Avoiding cotton cultivation on the same field for at least 3 years helps deplete the population of fungal spores in the soil.

Agronomic practices, such as planting in well-drained soil during optimal temperatures and managing weed populations, help reduce the incidence of infection.

Post-harvest management involves incorporating crop residues into the soil through deep plowing, which accelerates decomposition and reduces the survival of the pathogen.

When environmental conditions favor disease outbreak, targeted foliar applications of fungicides are recommended to protect the crop during the boll development phase.