TABLE 3--A summary of the minimum toxic and maximum non-toxic doses of insecticides ap- 
plied as sprays or dips to livestock as determined at Kerrville, Tex.--Continued 
Minimum 
toxic dose 
found 
Maximum 
non-toxic 
dose tested 
Chemical 
ORGANIC PHOSPHORUS COMPOUNDS-- Continued 
Percent Percent 
Malathion Calves 1-2 weeks ORS) 0 
Cattle adult P0) --- 
Sheep adult TO --- 
Goats adult TO --- 
Parathion Calves 1-2 weeks --- Os 
Sheep adult --- 0 
Goats adult sali 10 
Ronnel Calves 1-2 weeks 2 --- 
(Dow ET-57, Korlan) Cattle adult 2e5 --- 
Sheep adult Pes) --- 
Bayer L 13/59 Calves 1-2 weeks 0 --- 
(Dipterex ) Cattle adult 2.0 a 
4-tert-butyl-2-chlorophenyl Calves 1-2 weeks 200 an 
methyl methylphosphoramidate Cattle adult Ae --- 
( Ruelene ) Sheep adult BG --- 
Delnav Calves 1-2 weeks 5 52 
Cattle adult AS) aes 
CARBAMATES 
Sevin Calves 1-2 weeks 2.0 4.0 
Cattle adult 4.0 ae 
*DDT, TDE, Methoxychlor, Perthane, and Dilan were nontoxic to 1l- to 2-week old calves 
at 8 percent concentrations. 
insecticide left on hair, and that this effect was altered by the degree of hardness of the 
water used for dilution. 
Emulsifiable concentrates gave some real problems, many of them closely allied to 
those of suspensibility. Early observations indicated that the specific gravity of the mix- 
ture (insecticide, solvent, and emulsifier) was of importance. If the weight was less than 
that of water, the droplets came to the surface; if heavier, they settled to the bottom. If 
the mixture came to the surface, wind and sun evaporated the solvent, changing the basic 
formula and decreasing the liklihood that reemulsification would occur. There was also 
obviously a greater concentration of insecticide in the floating layer and a decrease in 
the water below it, In a dipping vat (bath), a submersed animal, on returning to the sur- 
face, could be coated with a heavy dosage of insecticide. Uneven control of parasites was 
inevitable. If in a spray device with delivery from the bottom, the first treatments were 
unusually light, the last unusually heavy, the latter leading the livestock poisoning. 
On the other hand, when specific gravity was high, the droplets settled out in a layer 
along the bottom. Settling in dipping vats, along with assorted dirt, hair, and debris, the 
143 
