CONTROL STUDIES 



Since the initiation of the current studies on Rhabdocline needle 

 cast, spray control plots at various plantations of the Northeast have 

 been maintained. It was thought that the use of spray programs to 

 provide acceptable disease-free trees would be economically justi- 

 fiable because of the high stumpage value of Douglas-fir for Christ- 

 mas trees. It seemed obvious that such a program should be initiated 

 bv a search of known fungicides in the hope of finding one or more 

 that would control R. pseudotsugae. 



In 1956 test plots were established at the Camden and Cortland 

 plantations in New York. Forty-five trees, with varying degrees of 

 infect ion. were selected in each plantation and given numbers. These 

 numbers were then randomly assigned to five different treatments, 

 using Snedecor's (53) random numbers tables. Ten trees were 

 assigned at each plantation to each of four different spray materials: 

 Bordeaux mixture, Lime-sufur, Ferbam, and Captan. Five trees 

 were sprayed with flour and Dreft (used as sticker and spreader 

 respectively) in water, as a check on the possible toxicity of this mix- 

 ture. The remainder of the infected trees in each plantation served 

 as untreated controls. 



In 1958 and 1959 additional plots were established in Douglas-fir 

 plantations on the University of Vermont forest at Jericho, Vermont, 

 and on a private estate at Woodstock, Vermont. Trees in both of 

 these plantations were heavily infected with both Rhabdocline 

 pseudotsugae and Adelopus gdumanni Rohde. Fifteen trees were 

 sprayed with one of three compounds: Cyprex, Actidione BR, or 

 Actidione S. Thus a total of forty-five trees was sprayed at each 

 location. All toxicants with their common names and concentrations 

 are given in Table 1. 



The fungicides were applied either by means of 5-gallon copper 

 knapsack-type or 3-gallon galvanized garden-type spray tanks. Only 

 the lower 6-foot portion of trees were sprayed except for trees 6 to 

 7 feet in total height wherein the entire tree was sprayed. 



The first spray was applied at Camden on May 22 and at Cortland 

 on May 28, in 1956. The sprays were then applied at weekly intervals 

 through the end of June. Two later applications, one on July 14 and 

 the other on July 23, were made at Camden when it was observed 



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