EFFECT OF SOIL MOISTURE AND SOIL TEMPERATURE ON BLACK SHANK DISEASE DEVELOPMENT IN TOBACCO
FORT DETRICK FREDERICK MD
Pagination or Media Count:
Phytophthora parasitica var. nicotianae, which causes black shank disease, infected susceptible Burley 21 and resistant Burley 11B tobacco plants growing in soil with moisture levels ranging from 19 to nearly 100 of moisture-holding capacity MHC. Most Burley 21 plants were killed at each of four moisture levels tested, although the disease developed slightly faster when moisture was high. Generally, Burley 11B and 37 resistant plants were diseased most severely when moisture was abundant, although a high incidence of the disease occurred in Burley 11B plants when moisture was 19 of MHC. The latter results suggest a relationship between moisture stress and disease severity. Burley 21 seedlings 2 12 inches high were killed between 16 and 30 C. Disease development accelerated with increasing temperature in this range. Burley 11B and 37 seedlings of the same age were killed at 28 to 30 C but not at 16 and 20 C, although infection occurred. In studies with older plants, Burley 21 plants in the 3- to 4-leaf and 7- to 8-leaf stages were killed at 24 and 31 C. Some Burley 11B and Burley 37 plants, inoculated in the 3- to 4-leaf stage, were killed at 24 and 31 C. When inoculated in the 7- to 8-leaf stage, some of these plants were killed at 31 but none was killed at 24 C. The optimum temperature for the growth of the fungus on oatmeal agar was 28 to 30 C.
- Medicine and Medical Research
- Soil Mechanics