Abstract
Inoculation experiments have established Aspergillus niger van Tieghem as the cause of Crown Rot of groundnut seedlings in East Africa. Typical lesions were produced by mycelial inocula on a suitable substrate, but no infection could be obtained by the use of conidia alone. The pathogenicity of five isolates of the A. niger group (Thom & Raper, 1951) could be closely correlated with oxalic acid production, but not with that of citric acid. Hypocotyl lesions were produced by treatment with growth products of pathogenic isolates in agar, and also by treatment with pure oxalic acid in comparable concentration. The optimum temperature for growth of A. niger on agar was found to be 37° C.; seedlings raised at 30–37° C. were most disposed to severe development of Crown Rot, and the progress of the disease was most rapid at these temperatures. Under experimental conditions, development of Crown Rot was most severe in a soil of light texture.
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