CIRCULAR No. 409 NOVEMBER 1936 
UNITED STATES DEPARTMENT OF AGRICULTURE 
WASHINGTON, D.C. ; 
THE EFFECT OF THALLIUM ON PLANT GROWTH 
By E. E. Horn, associate biologist, Justus C. Warp, associate pharmacologist, 
James C. Muncu, consulting pharmacologist, and F. E. Gariouas, biologist 
and director, Control Methods Research Laboratory, Division of Game Manage- 
ment, Bureau of Biological Survey 
CONTENTS 
Page Page 
aE FOCUChIONE meets been Bee ee Ne ee 1 | Experiments—Continued. 
OVICW? Omlterabure == sas ee See 1 Hie ldbimvestieat] Onsen 5 
EE EIMCI Tsay ee eye ie Pe ee | MOOG ITS Ons. oe ee ae 7 
Laboratory investigations__ .-.---------- De deliteratwee cited s= 262. 2 aa te 2 eee j 
INTRODUCTION 
For more than 10 years thallium compounds have proved useful in 
the control of the rat, the Zuni prairie dog, the California ground 
squirrel, and certain rodents that have been found particularly 
difficult to combat by other means. Several reviews have appeared 
discussing general features of the action of thallium and of its use in 
rodent control (7, 12, 19).1 Béttger (3) reported it to be widely 
distributed in the vegetable kingdom, finding it qualitatively in cer- 
tain mineral waters, wines, tobacco, beets, and chicory, but no pub- 
lished data have been found showing the occurrence of thallium in 
the soil. Buschke and Langer (6) stated that plants may take up 
thallium from the ground, since they found traces in the plant ash, 
and that if rat poison should be used on field or garden the thallium 
would pass into the plants and might cause poisoning. 
The question has been raised in several recent papers whether 
thallium applications to pasture lands in the control of ground squir- 
rels under field conditions will prove harmful to crop growth (4, 8, 
14, 15). This subject has been studied in detail for more than 10 
years, and the official agencies engaged in the distribution of thallium- 
treated material have always had this in mind (/2). 
REVIEW OF LITERATURE 
A detailed search of the literature shows that it is not possible to 
make any arbitrary statement regarding the toxicity of thallium to 
plants or animals, unless a number of circumstances are considered. 
Detailed data found in this search are recorded in table 1, with 
corresponding references to the literature, and results obtained by the 
authors also are included. 
1 Italic numbers in parentheses refer to Literature Cited, p. 7. 
78716°—36 1 
