Cs. Rothrock et al., THE INFLUENCE OF WINTER LEGUME COVER CROPS ON SOILBORNE PLANT-PATHOGENS AND COTTON SEEDLING DISEASES, Plant disease, 79(2), 1995, pp. 167-171
The influence of winter legume cover crops on soilborne plant pathogen
s and seedling diseases of cotton was examined at two locations over 2
yr. The Clarkedale site was a long-term cover crop experiment establi
shed in 1972. The Lewisville site was established in a production fiel
d with a history of cotton monoculture. Soil populations of Thielaviop
sis bosicola and isolation frequency of this pathogen from cotton seed
lings were reduced following a hairy vetch cover crop compared with wi
nter fallow at Clarkedale, the only site with moderate to high soil po
pulations of this pathogen. Isolation of Rhizoctonia solani from cotto
n seedlings and soil populations of Rhizoctonia spp. at planting were
increased following hairy vetch compared with winter fallow at Lewisvi
lle. A similar trend was found for Rhizoctonia spp. following hairy ve
tch at Clarkedale. Soil populations of Pythium spp. were greater at bo
th locations following a legume cover crop compared with winter fallow
; however, no differences among cover crop treatments were found for i
solation frequency of this genus from seedlings. The other cover crop
treatments (common vetch, hairy vetch plus rye, or crimson clover plus
rye) were intermediate between winter fallow and hairy vetch in their
influence on pathogen populations and isolation frequency. Bacterial
and fungal populations were greater in the cropping system containing
a hairy vetch cover crop compared with winter fallow at Clarkedale. Th
e influence of winter legume cover crops on the seedling disease compl
ex depended on the prevalent pathogens at each location. Winter legume
s do not appear to increase the risks of cotton seedling diseases suff
iciently to deter their use in reducing soil erosion and providing nit
rogen to a subsequent cash crop, and can reduce the risk of black root
rot.