Cylindrocladium black rot

Infected plant and shell
Roots usually become blackened and die back from the tips (left); the red resting bodies are typical of Cylindrocladium black rot, but are not always present (right)
Infected kernels
Kernels infected with Cylindrocladium black rot
Cause

Cylindrocladium crotalariae.

Damage

Major in the Burnett and Atherton Tableland. Black rot is caused by a soil-inhabiting fungus. Although wet conditions allow infection, particularly when plants are young, cylindrocladium black rot (CBR) is more evident when conditions turn dry and bushes start to wilt and die.

Symptoms

The taproot and side roots start to decay from the tip towards the main crown of the plant. There is internal dark brown discolouration of the roots, and sometimes the stems, but the only symptom seen on foliage is a general yellowing. Eventually the plant dies due to loss of the root system.

Red fungal structures (about pinhead size) may form on dead or diseased tissue. These do not usually occur on infected tissue in the South Burnett.

Spread

By infected plant parts and soil.

Management options

Nothing can be done for the current crop. The future of growing peanuts on that land seems to depend on surviving one or two bad crops, after which losses may be acceptable.

Cultural
Some growers on the Atherton Tableland use irrigation and fertiliser to reduce the effects of CBR. The lateral roots feed on the moisture and nutrients after the taproot has died. A rotation of two years maize followed by peanuts seems to be effective in keeping the inoculum to a low level on the tableland.

In the South Burnett, CBR can be quite severe in affected parts of a field for a few successive crops, but generally the severity decreases in subsequent crops. This does not appear to be the case on the Atherton Tableland, where the severity of the disease varies from season to season depending on weather conditions.

Damage to the root system by soil insects and nematodes can increase CBR infections.

Soybeans, lupins and lucerne are hosts for CBR.

Chemical registrations and permits
Check the Australian Pesticides and Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this disease on the target crop in your state or location. Always read the label and observe withholding periods.