Bibliography Tag: desiccation

Zhang et al., 2017b

Zhang, Ti , Johnson, Eric N., Mueller, Thomas C., & Willenborg, Christian J.; “Early Application of Harvest Aid Herbicides Adversely Impacts Lentil;” Agronomy Journal, 2017, 109(1), 239-248; DOI: 10.2134/agronj2016.07.0419.

ABSTRACT:

Applying harvest aid herbicides can dry down lentil (Lens culinaris Medik.) crops evenly and quickly, and can help control late-emerging weeds. However, improper application timing may reduce yield and quality, and leave unacceptable herbicide residues in seed, which can cause commercial issues when marketing lentil. The objective of this research was to determine the response of lentil to various application timings of glyphosate, saflufenacil, and the combination of these two herbicides. A field experiment consisting of a randomized complete block design was run at Saskatoon and Scott, SK, Canada in 2012, 2013, and 2014 to address the objective. Application of harvest aid herbicides before 30% seed moisture content reduced seed yield and thousand seed weight up to 25 and 8%, respectively. Moreover, application timings before 30% seed moisture resulted in lentil seed samples exceeding residue levels of 2.0 and 0.03 mg kg–1 for glyphosate and saflufenacil, respectively. Adding saflufenacil to glyphosate did not reduce glyphosate residue in lentil seed compared to glyphosate applied alone. However, this tank mixture significantly reduced seed residues of saflufenacil and improved crop desiccation compared with either glyphosate or saflufenacil applied alone. Our data lead us to conclude that a tank mix of saflufenacil+glyphosate should be recommended for crop desiccation and pre-harvest weed control in lentil over using either product alone. In addition, it is critical to ensure applications of glyphosate or saflufenacil are not made prior to 30% seed moisture in lentil crops. FULL TEXT


Zhang et al., 2017a

Zhang, Ti, Johnson, Eric N., & Willenborg, Christian J.; “Evaluation of Harvest-Aid Herbicides as Desiccants in Lentil Production;” Weed Technology, 2017, 30(3), 629-638; DOI: 10.1614/wt-d-16-00007.1.

ABSTRACT:

Desiccants are currently used to improve lentil dry-down prior to harvest. Applying desiccants at growth stages prior to maturity may result in reduced crop yield and quality, and leave unacceptable herbicide residues in seeds. There is little information on whether various herbicides applied alone or as a tank-mix with glyphosate have an effect on glyphosate residues in harvested seed. Field trials were conducted at Saskatoon and Scott, Saskatchewan, Canada, from 2012 to 2014 to determine whether additional desiccants applied alone or tank mixed with glyphosate improve crop desiccation and reduce the potential for unacceptable glyphosate residue in seed. Glufosinate and diquat tank mixed with glyphosate were the most consistent desiccants, providing optimal crop dry-down and a general reduction in glyphosate seed residues without adverse effects on seed yield and weight. Saflufenacil provided good crop desiccation without yield loss, but failed to reduce glyphosate seed residues consistently. Pyraflufen-ethyl and flumioxazin applied alone or tank mixed with glyphosate were found to be inferior options for growers as they exhibited slow and incomplete crop desiccation, and did not decrease glyphosate seed residues. Based on results from this study, growers should apply glufosinate or diquat with preharvest glyphosate to maximize crop and weed desiccation, and minimize glyphosate seed residues. FULL TEXT


Griffin et al., 2010

Griffin, James L., Boudreaux, Joseph M., & Miller, Donnie K.; “Herbicides As Harvest Aids;” Weed Science, 2017, 58(3), 355-358; DOI: 10.1614/ws-09-108.1.

ABSTRACT:

Herbicides used as harvest aids are applied at crop maturity to desiccate weed and crop foliage. Weeds present in the harvested crop can increase moisture content and foreign material, reducing grade and market price. Weeds can also delay the harvest operation and reduce harvest efficiency. Glyphosate can be used to desiccate weeds in glyphosate-resistant crops without concern for crop injury. Carfentrazone and pyraflufen-ethyl used as harvest aids can be effective in desiccating broadleaf weeds in corn and soybean. Paraquat, although effective on grass and broadleaf weeds when applied late season, can cause significant crop injury if applied too early. With expanded production of early maturing soybean cultivars in the mid-South (Arkansas, Louisiana, Mississippi, Missouri bootheel, and west Tennessee), presence of green stems, green pods, or green leaf retention, or combinations of these at harvest has increased. Interest in harvest aids has shifted to use as a crop desiccant. Paraquat also is an effective soybean desiccant, but application timing differs for indeterminate and determinate cultivars. Paraquat applied after soybean seed reached physiological maturity reduced number of green stems, pods, and retained green leaves present, allowing harvest to proceed 1 to 2 wk earlier than nontreated soybean. Seed moisture, foreign material, and seed damage also were reduced when paraquat was applied. FULL TEXT


Wigfield et al., 1994

Wigfield, Y. Y., Deneault, F., & Fillion, J.; “Residues of glyphosate and its principle metabolite in certain cereals, oilseeds, and pulses grown in Canada, 1990-1992;” Bulletin of Environmental Contamination and Toxicology, 1994, 53(4), 543-547; DOI: 10.1007/bf00199024.

ABSTRACT:

Glyphosate, sold under the trade names of Roundup R (for ground application) and Vision R (for forestry use), is a non-selective herbicide which is absorbed through the leaves and translocated throughout the whole plant. The herbicide, when applied close to harvest for late season weed control and possible harvest management benefits, can result in the presence of residues throughout the whole plant including the seed coat. In Canada, glyphosate is registered for pre-plant and post-harvest uses and until June 1991, it was not registered for direct application on crops. Diquat, a fast acting herbicide, is registered for desiccation of canola, mustard, field peas, flax, soybeans, and lentils. While diquat is effective as desiccant, it is not particularly effective in controlling perennial weeds and it is not registered for use on cereals. In June 1991, a temporary registration was granted for pre-harvest application on flax for control of quackgrass, seasonlong control of Canada thistle and perennial sow thistle and harvest management by drying down the crops. In June 1992, the same registration was granted for application on certain cereals (wheat and barley), oilseeds (canola/rapeseeds and soybeans) and pulses (peas and lentils), and in June, 1993 it was granted for malting barley. The pre-harvest use may also provide soil conservation benefits by reducing the use of cultivation as a means of weed control. The maximum residue limit (MRL) (Doliner and Stewart, 199 la) when crops are treated with the proposed label directions (single application at the rate of 0.89 kg/ha glyphosate and the time of 7-14 days before harvest) are shown in Table 1. Registration for use on beans has not been granted due to insufficient residue data.

However, because glyphosate is effective as herbicide and provides harvest management benefits, in 1990 questions were raised from Agriculture Canada field inspection staff regarding the potential misuse of the herbicide which at that time was not registered for pre-harvest use on crops. Thus a post-harvest survey was conducted to monitor glyphosate residues in these cereals, oilseeds and pulses grown during 1990-1992 period to check if the registration uses of glyphosate were being followed. This paper presents the 3-year monitoring results comprising 459 samples of 8 different crops grown in 7 different provinces in Canada. FULL TEXT


Cessna et al., 1994

Cessna, A. J., Darwent, A. L., Kirkland, K. J., Townley-Smith, L., Harker, K. N., & Lefkovitch, L. P.; “Residues of glyphosate and its metabolite AMPA in wheat seed and foliage following preharvest applications;” Canadian Journal of Plant Science, 1994, 74(3), 653-661; DOI: 10.4141/cjps94-117.

ABSTRACT:

In a 2-yr study at four locations in western Canada, residues of glyphosate and its major metabolite aminomethyl-phosphonic acid (AMPA) were measured in the seed and foliage of wheat (Triticum aestivum L.) following preharvest applications at rates of 0.45, 0.9 or 1.7 kg acid equivalent ha−1. Herbicide treatments were applied in early August to mid-September at seed moisture contents ranging from 52 to 12%. Glyphosate and AMPA residues in the seed increased as the rate of application increased, and decreased as the seed moisture content at the time of application decreased. However, when the maximum application rate of 1.7 kg ha−1 was sprayed at seed moisture contents of 40% or less, glyphosate residues in the seed were < 5 mg kg−1, the Maximum Residue Level recently established by Health Canada. Glyphosate and AMPA residues in the straw also increased with increasing application rate, but there was no consistent pattern in residues of either chemical with seed moisture content at the time of application. Physiological maturity of the crop, rainfall washoff, and application rate appeared to play important roles in determining the magnitude of glyphosate and AMPA residues in the seed and straw of wheat. Key words: Glyphosate, AMPA, residues, wheat, seed, preharvest application. FULL TEXT


Cessna et al., 2002

Cessna, A. J., Darwent, A. L., Townley-Smith, L., Harker, K. N., & Kirkland, K.; “Residues of glyphosate and its metabolite AMPA in field pea, barley and flax seed following preharvest applications;” Canadian Journal of Plant Science, 2002, 82(2), 485-489; DOI: 10.4141/p01-094.

ABSTRACT:

Maximum residue levels have been established by Health Canada for seed of several crops treated with preharvest applications of glyphosate, a common practice on the Canadian prairies. Residues of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA) were determined at crop maturity in flax seed at one site in western Canada and in the seed and straw of field pea and barley at another site following preharvest applications of the herbicide. Glyphosate was applied at rates of 0.45, 0.9 and 1.7 kg ha-1 to each crop in early August to mid-September at four stages of crop development. In all crops, mean residues of glyphosate and AMPA increased with increasing application rate of glyphosate and decreased when the herbicide was applied at later stages of crop development. FULL TEXT