H. glycines :4 



n'ent is carried out, in 1955 was groi-m solid v/ith soybeans, and soil 

 assay indicated a fairly imiform infestation throughout the field. 



Another phase of the work that I personally have followed, perhaps 

 most closely, has been chemical control. Me have leased the field 

 just mentioned for a period of five years. Plots twenty feet souare, 

 with four-foot x%Tide alleyways between, were set up for experimental 

 work. We established three replications and are using methyl bromide 

 at three rates: 1, 2, and 3 pounds per hundred square feet; D-D at 

 three rates: 20, ijO, and 60 gallons per acre; ethylene dibromide at 

 three rates: U|j 9 and 13 gallons per acre; telon at 20 and Uo gal- 

 lons per acre; nemagon at 3 and 5 gallons per acre; and the necessary 

 control plots. 



In gauging the effects of the chemicals, we took what we call a "white 

 cyst index." It was a means for rather quickly obtaining data on the 

 effective ness of the chemicals. Ife found that if one removes the 

 bean plants from the grotmd approximately 30 days after planting, the 

 white cysts can be seen and judged by an arbitrary rating scale. The 

 roots can either be washed by dipping in a bucket of water or, if the 

 soil is readily shaken off, the roots can be examined id.thout washing. 

 The white cysts are very easily seen. VJe used a rating scale of from 

 to 5. "0" represented no cysts being found in the examination of 

 from 10 to 20 plants from a plot. "5" represents the heaviest degree 

 of infection. Use of this method serves to give a good idea of the 

 level of infestation at the time the beans were planted, as, of course, 

 the white cysts had come from invasion by active, viable larvae in the 

 soil. 



Now, as to the results of the fumigation experiment. The plants in the 

 untreated check plots had index readings of about 5. VJhile we do not 

 claim- to have eradicated the nematode from the methyl bromide treated 

 plots, we were unable to find white cysts on the roots when they were 

 pulled as soon as one month after planting, so we gave these a rating 

 of for the time being. Telon, at 20 gallons per acre, was quite inef- 

 fective, but gave very good control at UO gallons per acre. Nemagon 

 was very good at 3 and 5 gallons per acre, particularly at the 5 gallon 

 rate. D-D was only fair at the 20 gallon rate and very good at UO and 

 60 gallons per acre. Ethylene diV^romide was somewhat eratic, in that 

 it seems the more we put on, the less control we had. Hovrever, we are 

 repeating this same test again to make sure we are not being unfair in 

 our appraisal of this material. 



Ue knew that methyl bromide would not be a practical field method of 

 control. However, we did want to learn if it could control the nematode, 

 as it would, perhaps, be useful for treating small spots or infested 

 objects. Methyl bromide did give the best looking plots. The 1 and 2 

 pound rates were about equal in effect, but at the 3 pound rate there 

 was some toxicity to the soybean plants. One difficulty was had in the 

 check plots. Wiere there was poor growth of the soybean plants, hence 

 little shading out of the weeds, control of the weeds was quite a problem, 



