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Yellow Sigatoka

Yellow Sigatoka

Mycosphaerella musicola

fungi

In a Nutshell

    Light green specks appear on the upper side of the leafLesions enlarge and form narrow, brown spots and later rusty red streaksRed streaks with yellow, water-soaked marginsLarge brown to black necrotic areas appear along the leaf margin

Hosts: %1$s

· Banana

Symptoms

The earliest symptoms can be found on the 3rd and 4th open leaf. Tiny, light yellow specks (1-2mm long) appear on the upper leaf blade, parallel to the secondary veins. These specks later develop into narrow, brown or dark green spots with a spindle shape. These lesions expand further parallel to the veins and form oblong rusty red streaks with water-soaked centers and yellow halos (4 to 12 mm in length). The centers of the streaks gradually turn gray brown to brown, a sign of necrosis. Along the leaf margins, they coalesce to form large, black or brown necrotic lesions surrounded by patches of yellow areas. The cracking of the leaves gives them a ragged appearance.

Trigger

Yellow Sigatoka is caused by the fungus Mycosphaerrela musicola and occurs throughout the world. It is one of the most destructive diseases of banana. It is more frequent at higher altitudes and cooler temperatures, or during rainy seasons in subtropical growing regions with warm environments and high relative humidity. The fungus survives in dead or living plant tissues, and produces spores that are spread by wind or rain splashes. The optimal growth temperature for the fungus is around 27°C and young leaves are the most susceptible. The disease reduces plant productivity, which in turn affects the size of the bunch and shortens the ripening time of the fruit.

Biological Control

Biological control with bio-fungicides based on Trichoderma atroviride have the potential to hinder the disease and are being tested for possible field applications. Bordeaux spray applied on pruning sites can hinder the propagation of the disease on these plan parts

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Fungicides containing mancozeb, calixin or chlorothalonil can be applied as foliar sprays when disease is not widespread. Rotations of systemic fungicides such as propiconazole, fenbuconazole or azoxystrobin also work fine. The rotation is important to prevent the build up of resistance in the fungus.

Preventive Measures

    Use resistant varieties (note that this can negatively impact taste)Leave sufficient space between plants to ensure good ventilationAvoid high soil moisture through good drainageClear fields and surroundings of weedsEnsure a balanced nutrition of the treesApply urea as nitrogen source to compromise fungal growth on the soilCut off infected leaves, then burn them outside of the plantation or bury themUse fertilizers high in potassium to minimize the infestation