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Rice Stem Rot

Rice Stem Rot

Magnaporthe salvinii

fungi

In a Nutshell

    Initial symptoms are small, irregular black lesions on the outer leaf sheath near water levelThe fungal growths empty the stem of its content, leading to early lodgingAt later stages of the disease, unfilled panicles and chalky grains are observed

Hosts: %1$s

· Rice

Symptoms

Symptoms are usually seen after the tillering stage. Initial symptoms are small, irregular black lesions on the outer leaf sheath near water level. As the disease advances, the lesion enlarges, penetrates the inner leaf sheath and the culm, producing brownish-black lesions. One or two internodes of the stem eventually rot and collapse (only the epidermis remains intact), leading to lodging, unfilled panicles, chalky grains or death of the tiller. Dark-greyish mycelium can be seen inside hollow, infected stems, with small, black sclerotia dotted over the inner surface.

Trigger

Infection is high on plants with wounds as a result of lodging or insect attack. The panicle moisture content and nitrogen fertilizer also influence disease development.

Biological Control

Methods to control stem rot include good field management practices, and the use of antagonistic organisms.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Chemicals such as fentin hydroxide sprayed at the mid-tillering stage, thiophanate-methyl sprayed at the time of disease initiation can reduce stem rot incidence. Other fungicides such as ferimzone and validamycin A also work effectively against the fungus.

Preventive Measures

    Keep updated on the available resistant varietiesDrain the field to reduce the proliferationReduce nitrogen content and perform split applicationsIncrease the content of potash to keep soil pH highCollect and burn any crop residue after harvest or let the straw decomposeAvoiding stagnation of irrigation waterTimely weed control