46 MASS. EXPERIMENT STATION BULLETIN 378 



Control of Cranberry Bog Weeds. (Chester E. Cross.) 



Kerosene. The water-white kerosenes of five different refining companies 

 were again tested for their vine-burning and weed-killing properties, with 

 results similar to those of 1939: the Atlantic, Colonial and Gulf kero- 

 senes Avere less harmful to cranberrj^ vines than the others tried; Shell 

 kerosene did more burning than the Shell product of last year. In order 

 of increasing toxicity to vines they stood this year as follows: Atlantic, 

 Gulf, Colonial, Shell, and Cities Service. 



The various kerosenes were all about alike as killers of grasses, sedges, 

 and rushes. Colonial and Shell were the most efifective on loosestrife. 



Studies were made of relative vine burn by kerosene under varying 

 conditions of humidity, sky, time of day, and wind. High relative humid- 

 ities correlated with severe vine injury; kerosene applied from 11a. m. to 



4 p. m. burned the vines, while applications made the same day from 



5 to 9.30 p. m. did no harm. Air currents are intimately associated in this 

 with the prevailing humidity; if the latter is high, winds make the vine 

 burn excessive; if low, they hasten the evaporation of the oil, and the vines 

 are not hurt. Kerosene always reduces the crop when applied after the 

 blossom buds are fully developed. 



Applied in small quantities to the bases of the plants, kerosene kills 

 bayberry and sweet gale bushes as it does hoary alders. A heavy spray 

 to the tops of these plants is equally effective. 



Ferric Sulfate. The injury to cranberry vines, reported by many growers, 

 can be avoided by spreading this chemical evenly and brushing it off from 

 the vines after it is applied. The margin in tolerance between weeds and 

 cranberry vines is rather narrow, and locally increased doses harm the 

 vines. Moisture on the vines at the time of treatment caused much injury. 

 Dry weather after the application makes the chemical more effective in 

 killing weeds and reduces the hazard to the vines. Midday applications 

 are best; late afternoon treatments, even when the vines seem dry, are 

 apt to be harmful. 



Ferric sulfate was rather widely used on bogs this year. It proved very 

 effective on horsetail, small ferns, royal fern, hardhack. wool grass (Scirpus 

 cyperinus), and spike rush or needle grass (Eleocharis) when a small hand- 

 ful was applied at the base of each plant. It works on the root system, 

 killing it completely. The cranberry vines remain unhurt if it is used 

 carefully. It is also effective used early in the season on asters, a broad- 

 cast of 15 to 20 pounds to the square rod being advocated. Needle grass 

 can also probably be controlled in this way, though the permanence of its 

 kill is uncertain. 



Broadcasts of 20 pounds of ferric sulfate to the square rod killed 90 

 percent of the rice cut-grass ("sickle grass"') even where the drainage 

 was only five inches. As cut-grass infests poorly drained areas mostly, 

 it is hard to control with kerosene. The bog soil should be kept as dry 

 as possible during and after the treatment witli ferric sulfate. 



Ferric sulfate was effective when applied early in the growing season. 

 Plots treated late in August and in September showed only moderate 

 kills of the weeds, and the vines were hurt in many cases. 



Fertrous Sulfate. A large number of plots treated in June and July proved 

 that dry applications of ferrous sulfate watered at once with a sprinkling 

 can are far more effective than those left to be dissolved by rain. 



A dry broadcast, 30 pounds to the square rod, killed 98 percent of 



