Field studies on the ringspot disease of Burley tobacco in Washington County, Virginia

Abstract

1. Steam sterilization of the tobacco plant bed did not control ringspot.

2. The virus was not transmitted from diseased to healthy plants by the common tobacco flea beetle (Epitrix parvula) although they lived and multiplied on tobacco plants within the cages.

3. The cucumber flea beetle (Epitrix cucumeris), leaf hopper (Empoasa fabea), Aphis (Macrosiphum solanifolii) and the lightning bug (Photinus scintillans) did not survive when caged on tobacco, and no infection was obtained with them. The tobacco worm (Phlegethontius quinquemoculata) survived but did not transmit ringspot.

4. Stick weed, sometimes called yellow crown beard, (Verbisina alternifolia) and sweet clover (Melilotus alba) were found naturally affected with ringspot, infection was readily obtained on tobacco with the expressed juice from these plants.

5. Twenty-five other species of weeds were tested for ringspot with negative results.

6. The rate of spread of the disease was not definitely determined.

7. The percentage of ringspot infection in ten counties in Virginia in 1927 was 2.5. In Washington County in 1928 it was 3 per cent, and in 1929, 7.6 per cent.

8. There was an average injury of 20 per cent to the affected plants

9. It is estimated that ringspot caused a total loss of $12,768.00 in Washington County in 1929.