Gray leaf spot of maize

C/O : Cercospora  zeae –maydis

• Prevalent in warmer and rainy season
• GLS was first reported in 2006 from Nepal.
• It became epidemic in the Dhungkharka VDC of Kavre Planchowk district and Kaleswor, Gotikhel VDCs of Lalitpur district of Nepal

Symptoms:

• Symptoms appear first on lower leaves before silking.
• Small, pinpoint lesions surrounded by yellow halos (more visible as leaf is backlit).
• Gray to tan lesions develops between the veins and are distinctly rectangular with smooth, linear margins along the leaf veins.

Lesions are most often confused with those of the bacterial leaf streak. Bacterial leaf streak lesion margins are usually more irregular or wavy in contrast to the smooth, straight lesions of gray leaf spot. 

Etiology:

• olivaceous-grey with white patches.
• conidiophores bearing fusiform conidia that emerge through stomatal pores in the plant epidermis

Favorable condition:

• warm temperatures, 27 °C.
• high humidity, relative humidity of 90% or higher for 12 hours or more.
• Extended periods of leaf wetness (~13 hours) allow infection of leaves

Survive and spread:

• Survive: Cercospora zeae-maydis overwinters in corn residue, allowing inoculum to build up from year to year in fields.
• Spread: wind borne conidia

Disease cycle: Polycyclic disease

Management

• Cultivation of tolerant varieties such as Ganesh-1, Manakamana-3 Manakamana-1, Hillpool yellow, Deuti.
• Spraying of fungicides such as; Carbendazim 50% WP (Bavistin, Benofate) 1gm or DiathaneM-4̊̊5 or SAFF 2gm/lit of water can help to manage the disease.