Graduate Thesis Or Dissertation
 

Influence of Norbak, Dacagin, and Vistik on spray drift, volatility, adherence, and efficacy of several herbicides

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  • Norbak, Dacagin, and Vistik, when mixed with a spray solution, each have the unique property of increasing the viscosity of that solution. This property has been used commercially for the reduction of spray drift. Studies were made of the drift control adjuvants to determine the following: (1) the effect of the adjuvants on the phytotoxicity of selected herbicides to several crops, (2) the effect of the adjuvants on the herbicidal efficacy of paraquat, (3) the effectiveness of the adjuvants in reducing spray drift under field conditions, (4) the effect of the adjuvants in preventing amitrole-T from being washed off plants with simulated rainfall, and (5) the ability of the adjuvants to reduce vapor loss of 2,4-D ethyl ester when applied in combination to plant surfaces. Field experiments in which adjuvants were sprayed in combination with 2,4-D amine on wheat and corn, dicamba on barley, and MCPA on red clover, indicated that only in the case of Vistik applied with MCPA at rates of 1.0 and 1.5 lbs./A. was there a reduction in herbicidal selectivity. This reduction was very slight. The adjuvants were each very effective in reducing spray drift in paraquat field studies. Injury to test plants 50 feet from the spray swath was less than five percent for the paraquat solution containing an adjuvant as compared to 20 percent for the solution without an adjuvant. Studies were conducted to determine whether the adjuvants would substitute for the wetting agent X-77 in paraquat applications under field conditions. Thirty-two plant species were sprayed in each plot and visually evaluated several weeks later for injury. Results showed that the adjuvants were not effective substitutes for X-77. On the other hand, the addition of Dacagin or Vistik to the paraquat solution did not decrease the herbicidal efficacy when X-77 was used. Norbak decreased the herbicidal efficacy of paraquat with or without the addition of X-77. A study to determine the effectiveness of the adjuvants in preventing amitrole-T from being washed off plant surfaces was conducted. Tomato plants were sprayed with an amitrole-T solution containing adjuvant and washed with simulated rainfall at various time intervals following the spraying. The adjuvants proved ineffective in preventing the amitrole-T from being washed off the plants. In another experiment bean plants were sprayed with a 2,4-D ethyl ester solution in which adjuvant was mixed. These plants were placed in a plastic bag enclosure with untreated bean plants to study the effectiveness of these adjuvants in reducing vapor loss of 2,4-D from the treated beans. Results suggested that only Dacagin had properties that reduced vapor loss, and this reduction was slight. Throughout the above experiments Norbak noticeably decreased the efficacy of the herbicides. This decrease is attributed to the reduction in the number of spray droplets per unit area in the spray swath.
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