ANNUAL REPORT, 1941 39 



Paradichlorohenzene. It was observed <n August 1940 that poison ivy {Rhus 

 Toxicodendron) growing on areas of bog treated with 1200 pounds of this chemical 

 to the acre and then resanded with half an inch of sand lost all its leaves, while 

 cranberry vines on the same ground showed no injury. Cranberry bog plots with 

 poison ivy were treated in September 1940, with amounts ranging from 800 to 

 5400 pounds per acre and then resanded with half an inch of sand. All these 

 plots, except that which received 800 pounds per acre, showed a kill of three 

 fourths of the ivy in the summer of 1941, with no injury to the cranberry vines 

 or their crop. Paradichlorobenzene applied in June, July, and August, 1941, 

 killed the ivy well, 1200 pounds per acre being as effective as greater amounts. 

 A cover of three quarters of an inch of sand seemed necessary for the best results. 

 Frost flooding two weeks after the chemical was applied did not seem to affect 

 the kill of ivy. 



Paradichlorobenzene, 1200 pounds per acre applied in June, July, and August 

 and covered with three fourths of an inch of sand, killed 80 percent of consid- 

 erable growths of chokeberry {Aronia melanocarpa), this weed losing all its 

 leaves and its roots becoming brown and rotten in 12 days. 



The following weeds endured paradichlorobenzene treatments as well as cran- 

 berry vines: Horse brier {Sniilax rotundifolia), saw brier (5. glauca), small bramble 

 {Riihus hispidus), coarse bramble {R. villosus), horsetail (Equisetum), asters 

 {A. spectabilis and A. multiflorus) , sphagnum moss, sensitive fern {Onoclea 

 sensibilis), shield fern (Thelypteris palustris), bayberry (Myrica caroliniensis), 

 sweet gale (Myrica Gale), wild bean {Apios tuherosa), red maple {Acer rubrum), 

 hardhack {Spirea tomentosa), three-square grass {Scirpus americanus) , spike rush 

 {E'eocharis tenuis), and partridge pea {Cassia chamaecrista) . 



Naphthalene. Tests with naphthalene at 800, 1600, and 2400 pounds per acre 

 were made in June, Jul}', and August on poison ivy and other beg weeds. The 

 chemical was broadcast by hand and covered with sand as in the paradichloro- 

 benzene treatments. It failed to kill more than 10 percent of poison iv}' even 

 where it was applied in greatest quantity and had no effect on horsetail, hardhack, 

 soft rush, reed canary grass, three-square grass, royal, sensitive, and shield ferns, 

 or cranberry vines. 



Ferric Sulfate. This year 32 plots with many kinds of cranberry bog weeds 

 were treated with ferric sulfate at various rates. A carpet of young royal ferns 

 on a peat-bottcmed bog with poor drainage was killed with a broadcast treatment 

 of 15 pounds per square rod, no cranberry vines or flower buds being hurt by it; 

 10 pounds per rod killed only 70 percent of the ferns and 20 pounds killed 8-10 

 percent of the cranberry branches. 



One handful of ferric sulfate proved enough to kill 5-7 medium-sized cinnamon 

 ferns. The vines around ferns treated with this amount under dry conditions 

 showed no injury. 



Ferric sulfate, 15 pounds per square rod, completely eliminated shield and 

 sensitive ferns. 



Single handfuls of ferric sulfate killed 2-4 clumps of soft rushes {Juncus effusus). 



Spike rush {Eleocharis) was killed easily with 15 pounds of ferric sulfate or 

 35 pounds of ferrous sulfate to the square rod, but ferrous sulfate needs rain or a 

 sprinkling of water to make it effective. 



Ferric sulfate at 15-20 pounds per square rod must be used in late May or early 

 June to be effective on rice cut-grass. This weed when 6 or more inches high, 

 in July and August, tolerated a great deal of the chemical. 



A little ferric sulfate at the base of each shoot was effective on wild bean. 

 A handful was enough for at least 6 shoots. 



