Stem blight (Phoma exigua Desm.)

Introduction

The disease is considered as a minor disease in India. The disease is first reported by Dayakar Yadav and Sukumar (1988) from Tail Nadu during July to October 1985.

Symptoms

It attacks tender stems which become pale brown and swollen. The leaves wither and the stem usually breaks at the point of infection. Pycnidia develop in concentric rings inside the necrotic spots.

Causal organism

Phoma exigua

Systematic position

Predisposing factors

Moderate temperature and high soil moisture conditions favours the disease development.

Disease cycle

The pathogen forms sub-epidermal pycnidia in concentric rings. The pycnidia are globose to sub-globose or obpyriform and ostiolate. Pycnidia wall is pseudoparanchymatous, with outer cell dark and thick walled and inner cells osodiometric and hyaline. Conidiogenous cells are indistinguishable from inner cells. Conidia arise as buds in basipetal succession from the apex of conidiogenous cells.

Control

Cultural control: The affected shoots should be removed and burned. Proper intercultural operations such as deep digging and ploughing to be done.

Chemical control: The cuttings should be soaked in 0.1%  Dithane M-45 before planting.

Biological control: Soil application of Nursery guard (A bioformulation made of Trichoderma pseudokoningii) reduces the disease severity.

Related literature

Dayakar Yadav BR, Sukumar J, (1987) Occurrence of a new stem- blight and collor- rot disease of mulberry from India.  Sericologia, 27(2): 205-206.