64 MASS. EXPERIMENT STATION BULLETIN 441 



leaves was caused by the naphthalene acetic acid on Wealthy, Early Mcintosh, 

 and Melba; while Golden Delicious, Richared, Blackmack, Red Astrachan, Ken- 

 dall, and Lobo varied from no apparent injury to moderate injury. 



Limited trials were also made with a new thinning mixture which the Delaware 

 Station reported as showing much promise. The mixture consisted of poly- 

 ethylene polysulfide (Goodrite p.e.p.s.) and a complex product of zinc dimethyl 

 dithiocarbamate "Zimate" with cyclchexylamine. It was used at the rate of 2 

 pounds of Goodrite and 1/8, 1/4, and 1/2 pound of the "Zimate" complex per 

 100 gallons. Applications were made on single branches of several varieties at 

 one and two weeks past full bloom. Under the conditions of the test none of the 

 sprayed branches showed a significant reduction in set over the checks. 



Chemical Control of Poison Ivy and Other Weeds. (J. S. Bailey.) Poison ivy 

 is often a serious pest in orchards where it grows under fruit trees, often in rank 

 profusion. Workers are sometimes seriously poisoned when picking up dropped 

 fruit at harvest time or when working in the orchard at other times. During 

 1946, several materials were used as sprays in an attempt to kill this pest. Four 

 formulations of the new weed killer, 2, 4-P, were tried. Two of these were esters, 

 one a butyl and the other a methyl ester. Both of these were tried at the usual 

 strength of 1,000 p. p.m. and at 2,000 p. p.m. None of the four formulations was 

 effective. Mixtures of several different concentrations of ammonium thiocyanate 

 with tar acid oil and kerosene were tried. These killed only the tops and new 

 tops developed from the old roots. A proprietary mixture of sodium chlorate 

 and a deflagration agent was also tried, used at 1 pound per gallon of water. This 

 was more effective than the 2, 4-D sprays but eradication was not complete. 

 As in 1945, ammonium sulfamate proved to be the most effective eradicant for 

 poison ivy. At % pound per gallon it was 90 percent effective, and at 1 pound per 

 gallon it was almost 100 percent effective. 



American bamboo (Polygonum Seiboldii De Vriese) is one of the most persistent 

 and fast growing weeds imaginable. It is not a common weed, but where it has 

 become established, it can take over large areas in a short time. Two ester for- 

 mulations of 2, 4-D at single and double strength were tried, without effect other 

 than a little twisting of the tender tips. Two applications of ammonium sulf- 

 amate at 1 pound per gallon, the first June 26 and the second August 8, failed to 

 kill this pest. 



Ammonium sulfamate is very toxic to peaches and cultivated blueberries but 

 harmless to apple trees four years old or older when spra\'ed on weeds under them. 

 Its effect on four-year-old pear, plum, and cherry trees was tested by applying 

 the spra}' on the weeds around them at 1 pound per gallon, 1 gallon per 100 square 

 feet. One spray was applied June 25 and a second September 6. No visible 

 effects have been observed on the trees; so that material appears to be safe for 

 use around cherries, plums, and pears, at least after they are four years old. 



A proprietary mixture of sodium chlorate and a deflagration agent was also 

 found to be safe around four-year-old cherries, plums, and pears when used at 

 1 pound per gallon, 1 gallon per 100 square feet. This mixture is toxic to cul- 

 tivated blueberries. 



Witch grass, sometimes called quack grass or twitch grass, is often a problem 

 around young trees in an orchard. Previous experience indicated that fall applica- 

 tions of ammonium sulfamate were more effective than sum.mer applications. 

 A series of plots was laid out in the summer of 1946 to test the effectiveness of 

 ammonium sulfamate and a proprietary mixture of sodium chlorate at different 



