28 MASS. EXPERIMENT STATION BULLETIN 361 



Because trellis wires cannot be easily or satisfactorily painted, the matter of 

 an inert wire offered a further problem of study. Different kinds of wire were 

 obtained for experimental tests. After exposure to burning sulfur fumigation in a 

 moist atmosphere, the wires were scraped to remove the chemical residue pro- 

 duced from the reaction, and 5 percent suspensions in distilled water were made. 

 The filtrates were applied to lettuce and tomato leaves with an atomizer and the 

 results noted (Table 17). 



Table 17. — Action of Burning Sulfur Fumigation on Wire and Toxicity 

 OF Extract of the Resulting Residue to Plant Foliage 



Degree of Injury 



Type of Wire Residue from Extract Price' 



• — per Cwt. 



Lettuce Tomato No. 16 Wire 



Stainless SteeU None None None $76 . 75 



Bethanized Steel^ Thick white Severe Severe 7.045 



Tinned SteeU Moderately rusted None None 6 . 345 



Zinc Galvanized Iron Thick white Severe Severe 5.995 



Black Enameled Copper2 None None None 10.000 



Uncoated Steel Wire 6 . 75 



'Furnished tlirough the courtesy of Bethlehem Steel Company, Bethlehem, Pennsylvania. 

 -Furnished through the courtesy of Essex Wire Corporation, Detroit, Michigan. 

 'Prices are of December 1, 1936. by Philip A. Rand, Boston, Massachusetts. 



Stainless steel wire is steel throughout with some alloys. Bethanized steel 

 wire is a special zinc galvanized steel wire. Tinned steel wire is coated with tin. 

 Black enameled copper wire is coated with a black enamel. These wires were 

 compared with zinc galvanized iron wire, the common grade of wire used in the 

 greenhouse for supporting trellised plants. The 5 percent extracts of the residues 

 from the zinc-coated wires were very injurious to lettuce and tomato foliage, 

 but extracts of residues from tinned, enameled, and stainless steel wires were not. 

 The use of zinc galvanized wires in greenhouses where sulfur is burned invites 

 serious drip injury to the succeeding planting. The injurious substance formed 

 is zinc sulfate and the amount of damage is obviously influenced by the amount 

 of sulfur burned and moisture conditions. Tinned steel wire, which compares 

 favorably in price with galvanized iron wire, reacted with the sulfur gas, judging 

 from the presence of a moderate amount of rust-colored residue, probably iron 

 sulfate; but a 5 percent extract of it was not injurious to lettuce and tomato 

 foliage. 



In a further experiment the percentage of water-soluble material formed by the 

 reaction and the character of the soluble residue were determined. Water ex- 

 tracts of the.se residues (5 and 2)4. percent strength) were atomized on tomato 

 foliage for toxicity values (Table 18). The percentage of soluble material in the 

 residues was most pronounced with Bethanized zinc galvanized wire. The severity 

 of injury was definitely correlated with zinc sulfate. The 5 percent extracts of 

 the residues from tinned and uncoated steel wires were only slightly injurious 

 and the action of a 2)^ percent extract was negligible. Therefore, uncoated or 

 tin-coated steel wire would be preferable to zinc galvanized wire in greenhouses 

 so far as compatibility with burning sulfur fumigation is concerned. The cost 

 of the stainless steel wire, which did not react, is, however, prohibitive. 



