The Fusarium Dry Rot

A number of crops, with potatoes being the most prominent are affected by dry rot decomposition in storage. Its cause can be traced to the 'Fusarium fungi' which also causes seed decay and wilting in the same crops. Among the many varieties of the Fusarium fungi, Fusarium sambucinum is the most commonly found to affect crops. Fusarium infections are either seed-borne or soil-borne or both. The fungus finds it way into potato tubers through abrasions and injuries on the tuber. These wounds are caused when the potatoes are harvested and while handling them. Fusarium doesn't grow below 40 degree Fahrenheit and rapidly grow at temperatures above 50 degree Fahrenheit.

Identification / Detection / Symptoms

Symptoms for dry rot are flaky decay in the tuber with red, yellow, brown or white fungal growth. Vascular discoloring in the stem may also occur in some cases. In the early stages of infection dark surface depressions start forming on the tuber. Later the tuber skin crumples in concentric rings. The pathogen begins decomposing the center of the tuber and then affects the remaining tuber by moving outwards in a circular fashion rotting out the center.

Control

Since the major entry point for the Fusarium fungus is wounds on tubers, it is advisable to preserve harvested tubers at 55 – 65 Fahrenheit and 90-95 percent relative humidity to ensure efficient wound healing. The tuber surface can also be coated entirely with the chemical Thiabendazole (TBZ) as it has anti-Fusarium properties.

The following proactive measures also help preventing dry rot

1. Usage of only certified seeds for planting. Further examination of procured seeds to eliminate any possibility of planting a seed with dry rot.

2. Regular disinfection of the seed storing facility, seed cutters and handling equipment.

3. Elimination of any potential moisture sources within the proximity of storage facilities.

4. Avoiding bruises while harvesting drastically reduces chances of infection. Heating the tubers to above 50 degree Fahrenheit minimizes the probability of bruising as cold tubers are highly prone to shattering.

5. Shielding the seed from sunlight and wind while planting as dehydrated seeds are very weak.

6. Timely inspection of stored tubers for obvious dry rot and grading out rotten pieces.

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