Feb. 7, 1916 
Further Studies on Peanut Leaf spot 
895 
is realized, of course, that these figures represent only an approximation, 
because the method itself is inexact. It is believed, however, that the 
approximated losses in yields of from 5 to 20 per cent given in Table I 
are reasonable, when one considers that there has been a loss to the plant 
of about 35 per cent in its active leaf area. 
TESTS ON DISSEMINATION OF LEAFSPOT BY AIR AND WIND 
Previous work on air currents as an agency in the dispersal of the leaf- 
spot fungus yielded only negative results. 1 It was believed, however, 
in spite of this negative evidence, that conidia are carried short dis¬ 
tances by the wind. 
The purpose of the tests herein reported was not only to determine 
whether or not the wind acts as an agent in dissemination of the conidia 
of Cercospora per sonata, but also to ascertain the conditions of tempera¬ 
ture and humidity which might influence its maximum or minimum 
prevalence in the air. The tests were conducted at Eutaw and Auburn, 
Ala. The tests at Eutaw, Ala., at which place 210 exposures of plates 
were made, covered the entire period, nights as well as days, from August 
9 to August 26, with the exception of August 15 and August 22. The 
tests at Auburn, Ala., were conducted from September 6 to September 
11 and were made to substantiate the tests made at Eutaw, Ala. 
The method formerly employed consisted in the exposure for varying 
lengths of time of sterile agar in Petri dishes. This method is open to 
objection for the reasons that at certain times the conidia of Cercospora 
personata germinate poorly or not at all and the development of colonies 
proceeds so slowly that they are likely to be obscured by more rapidly 
developing forms. It was decided, therefore, to use essentially the 
method employed by Burrill and Barrett 2 in their study of the dispersal 
of Diplodia zeae . Stations 2, 4, 6, and 8 feet distant from the nearest 
peanut plant were established. A frame to hold the exposure plates in 
a vertical position about 8 inches from the ground was made. This 
frame could be moved at the beginning of each exposure, to permit the 
plates to face toward the prevailing wind. Glass plates 4 by 5 inches 
were smeared with glycerin only on the side directed toward the peanut 
plants. Four sets of exposures of three hours duration each were made 
during the period from 6 a. m. to 6 p. m. One set of exposures of 12 
hours duration was made nightly from 6 p. m. to 6 a. m. Rains inter¬ 
fered somewhat with this routine. Plates exposed during a rain were 
washed off, and those exposed in the periods following rain were 
found to be free from conidia. Readings of the temperature and rela¬ 
tive humidity were made at the beginning of each set of exposures. The 
1 “All attempts to gain definite data showing that the wind is a carrier of the conidia have thus far been 
unsuccessful.” (Wolf, F. A. Eeafspot and some fruit rots of peanut. Ala. Agr. Exp. Sta. Bui. 180, p. 
134. 1914-) 
2 Burrill, T. J., and Barrett, J. T, Ear rots of corn. Ill. Agr. Exp. Sta. Bui. 133, p. 63-109, n pi. 1909. 
