Collar rot

Infected kernels and stem
Affected pods go grey inside in the early stages, then the whole pod rots (left); note the characteristic small black resting bodies on the stem (right)
Infected and healthy plants
Collar rot or lasiodiplodia: bushes rapidly wilt and rot at ground level
Cause

Lasiodiplodia theobromae.

Damage

Major problem in the Central and South Burnett, but is known in all peanut-growing areas.

Losses can be severe, up to total crop loss across an entire paddock. The disease seems to be worse where the soil is degraded through erosion or scalping during land levelling.

Symptoms

A rapid collapse of plants due to complete rotting of the roots and stems at ground level. Plants die throughout the season. Infection occurs at soil level where stems and crowns suffer from heat stress, soil abrasion or drought.

Management options

Nothing can be done for an affected crop.

Cultural
Maintain light irrigations where possible, so the plant can survive on surface roots. Do not delay harvest.

Rotation of at least two years in other crops should reduce the level of spores in the soil.

To minimise risk, plant early and consider planting on beds to obtain ground cover before the middle of summer.

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.