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Effect of Preharvest Glyphosate Application on Seed and Seedling Quality of Spring Wheat (Triticum aestivum)
Author: Joseph P. Yenish and Frank L. Young (W.S.U., & USDA)
Date Created: June 07, 2000
Last Reviewed: February 14, 2007
Document Source: Weed Technology, Volume 14:212-217 Summary · Studies were conducted to determine effects of preharvest applications of glyphosate on the seed and seedling quality of ‘Alpowa’ and ‘Penawawa’ soft white spring wheat (Triticum aestivum) varieties. · Glyphosate was applied at 0.62 or 0.84 kg ae/ha at the milk (Zadoks’ scale 70 to 79), soft dough (Zadoks’ scale 85), or hard dough stage (Zadoks’ scale 87) of wheat development; 7 d following the hard dough treatment; and 1 d prior to wheat harvest. · In harvest aid applications, wheat yields were reduced only with glyphosate applied at the milk stage of development. Yield reduction ranged from 20 to 77% depending on the year, variety, and glyphosate rate. Likewise, kernel weight and germination were affected only by glyphosate applications at the milk stage with reductions from 19 to 73% and from 2 to 46% for kernal weight and percent germination, respectively, compared to untreated wheat. · Using wheat from harvest-aided glyphosate treatments at the milk stage as seeds the following year resulted in reductions ranging from 28 to 99%, 19 to 39%, and 12 to 97% for seedling density, plant height, and seed yield, respectively, compared to seeds from untreated wheat. · In this study, wheat seed and seedling quality following preharvest glyphosate applications were most greatly influenced by crop maturity stage at time of application than by herbicide rate or variety.