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Comparison of Salt and Ester Formulations of Picloram

Published online by Cambridge University Press:  12 June 2017

R. W. Bovey ,
M. L. Ketchersid  and
M. G. Merkle
R. W. Bovey
Affiliation:
Crops Research Division, Agr. Res. Serv., U.S. Dep. of Agr., Dep. of Range Science
M. L. Ketchersid
Affiliation:
Dep. of Soil and Crop Sciences, Texas A&M University, College Station, Texas
M. G. Merkle
Affiliation:
Dep. of Soil and Crop Sciences, Texas A&M University, College Station, Texas
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Abstract

Under Texas conditions, the potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram) usually was more effective than the isooctyl ester formulation for control of live oak (Quercus virginiana Mill.), yaupon (Ilex vomitoria Ait.), winged elm (Ulmus alata Michx.), huisache (Acacia farnesiana (L.) Willd.), and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Possible reasons for the difference in effectiveness of picloram formulations were studied in the laboratory. Extensive degradation of the ester of picloram (96%) occurred in open Petri dishes after 72 hr exposure to ultraviolet (uv) light, compared to a loss of 26% for the salt of picloram. Forty-five percent of the isooctyl ester of picloram was lost at high temperatures (60 C), whereas only 2% of the potassium salt of picloram was lost after 1 week at 60 C from open Petri dishes in a dark oven. Application of the ester to soils reduced thermal and ultraviolet light degradation losses compared to losses from open Petri dishes. Loss of the ester was greater when applied in diesel oil to Petri dishes than in either water or paraffin oil. The salt of picloram leached most after 12.5 cm simulated rainfall in soil columns to the 17.5 to 30-cm level (907 μg), followed by the acid (360 μg), and last the isooctyl ester (0 μg). However, considerable acid (161 μg) was recovered at the 32.5 to 45-cm depth from the isooctyl ester treatment exposed to wet soils for 3 days, indicating hydrolysis of the ester to acid.

Type
Research Article
Information
Weed Science , Volume 18 , Issue 4 , July 1970 , pp. 447 - 451
Copyright
Copyright © 1970 Weed Science Society of America 

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References

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