Ring rot increase in potato seed lots having known quantities of infection

Summary

One-bushel samples of potatoes, each containing a “trace” of ringrot, were sent from Maine, Minnesota, Nebraska, New York and North Dakota to the Wyoming Agricultural Experiment Station, where they were grown in 1942 to determine the amount of ring-rot increase in the crop.

Each state sample was divided according to tuber size and planted separately either as whole tubers or as cut seed pieces. Ring-rot infection in each lot was determined both by plant symptoms and by the gram-stain method. The per cent of ring-rot by the latter method varied from 0.63 to 2.31 per cent in the five lots from the different states. Thus, the samples with a “trace” of disease produced an average of 1.31 per cent of ring-rot in the subsequent crop.

In addition, larger amounts of ring-rot were introduced in healthy seed, one-half of which was treated and the other one-half left untreated. The percentages of ring-rot introduced in the different lots were as follows: 0.10, 0:25, 0.50 and 1.00.

The resulting ring-rot in the treated lots ranged from 0.60 to 2.58 whereas in similar untreated lots it ranged from 1.48 to 18.69 per cent.