Watermelon green spot

The fungus overwinters in plant debris and soil, serving as a persistent inoculum source for the subsequent growing seasons.

Pathogen dispersal occurs mainly through wind currents and splashing rain, which carry spores from infected leaves to healthy ones.

Upon germination, the fungal spores penetrate the host cuticle, establishing systemic infection within the leaf and stem tissues.

The biological cycle of the pathogen is highly dependent on environmental moisture, which allows the mycelium to spread rapidly across the plant.

The earliest symptoms present as small, chlorotic green spots on the leaves, which gradually evolve into necrotic brown lesions.

In many cases, the centers of these spots dry out and fall away, resulting in a "shot-hole" effect on the leaves of the watermelon plant.

Elongated lesions or ulcers may appear on the vines and petioles, weakening the structural integrity of the plant during rapid growth.

Fruit symptoms include small, sunken, water-soaked spots that can eventually enlarge, leading to secondary rot and tissue degradation.

• small chlorotic spots
• necrotic lesions
• vine ulceration
• fruit rot
• foliar blight

The development of green spot is favored by high relative humidity (above 85%) and moderate temperatures ranging from 20°C to 28°C.

Prolonged periods of leaf wetness, often caused by heavy dew or frequent rainfall, are critical for successful fungal penetration.

Poor air circulation within dense plantings prevents the foliage from drying, creating an ideal environment for rapid disease progression.

Overhead irrigation systems often exacerbate the disease by spreading spores from infected plants throughout the field via water droplets.

Stress factors, such as improper fertilization or insect damage, increase the susceptibility of the crop to pathogen colonization.

The primary impact of the disease is the substantial reduction of the functional leaf area, which severely limits plant photosynthesis.

Infected plants exhibit stunted growth, resulting in significantly lower yields and poor fruit development throughout the season.

The disease decreases the market value of the harvest, as cosmetic lesions make the watermelons unattractive for commercial distribution.

Severe epidemics can lead to total crop failure, as the rapid spread of the fungus causes complete senescence of the foliage.

Economic losses are further compounded by reduced storage longevity, as infected fruit are highly prone to rapid post-harvest decay.

Implementing a strict crop rotation schedule is essential to break the pathogen's life cycle and reduce the soil inoculum pressure.

Sanitation practices, such as removing and destroying crop residues immediately after harvest, are vital to minimizing future infection risks.

Regular application of protective and systemic fungicides is recommended when environmental conditions are conducive to disease development.

Transitioning from overhead to drip irrigation significantly reduces leaf wetness and helps manage the spread of fungal spores.

Selecting resistant cultivars and ensuring adequate plant spacing are proactive measures that enhance the overall resilience of the crop.