Feb. 7,1916 
Further Studies on Peanut Leaf spot 
901 
previously reported, is due in part to the fact that grasshoppers and 
certain other insects are carriers of the leafspot organism. 
It might be interesting to note in this connection that it seems to be 
generally true that peanut fields in which grass and weeds had been per¬ 
mitted to grow unmolested, as exemplified by fields 4 and 6 in Table I, 
and which consequently afforded a more attractive feeding ground for 
grasshoppers, are much more severely attacked by Cercospora than those 
in which good cultivation had been given. Several small fields have also 
been found upon which chickens and turkeys ranged in which leafspot 
was doing inappreciable harm, while fields somewhat farther away from 
the farm buildings were seriously affected. It is believed that the rela¬ 
tive freedom from leafspot here observed is to be attributed largely to 
the destruction of the insects by fowls. 
In most cases no attempt was made to determine the presence of other 
fungi upon the insects taken. Among the other forms noted, however, 
were Helminthosporium Ravenelii B. and C., an organism very abundant 
upon the inflorescence of Sporobolus indicus; Puccinia cassipes B. and C., 
which is parasitic on species of Ipomoea, a common weed; and species of 
Altemaria and Fusarium. According to an estimate made, a single 
fecal deposit of a grasshopper contained 2,500 conidia of Helminthosporium 
Ravenelii . A katydid taken at Marion Junction and one at Auburn each 
voided a vast number of morning-glory rust spores. Insects 21 to 28 
(Table IV) indicate the manner in which this form may carry infections 
for short distances. The blister beetle is another insect which feeds 
upon peanut plants and which therefore discharges conidia from its 
alimentary canal. The other species of insects taken appear to carry 
conidia only upon their bodies. It seems very probable, judging from 
the evidence at hand, that any insect which feeds upon peanut foliage is 
a disseminator of leafspot, and that any of them which frequent peanut 
fields may serve as carriers. 
SUMMARY 
(1) Rotation by itself is not effective under field conditions in 
eliminating leafspot, as evidenced by a field in which peanuts had not 
been grown for 11 years and in which 95 per cent of the plants were 
diseased by August 31, with an estimated loss in yield of 19.5 per cent. 
(2) Seed disinfection with copper sulphate or formaldehyde before 
planting does not prevent leafspot. Shelling peanuts before planting to 
eliminate the danger of infection from conidia which may have been 
adhering to the surface of the shell does not prevent the disease. Seed 
treated in these ways, when planted on land which had previously borne 
diseased peanuts, produced a crop which was 100 per cent diseased. 
Seed treated and planted on soil which had borne no peanuts for at least 
four years previously produced a crop 13 per cent of whose plants were 
more or less affected with leafspot. Crop rotation, therefore, when com¬ 
bined with seed treatment, will not eliminate leafspot. 
