Whose Jurisdiction Is Home Contamination? Para-Occupational ‘Take-Home’ Herbicide Residue Exposure Risks among Forestry Workers’ Families in South Africa

Para-occupational “take-home” exposure risks among forestry workers and their families in low-and middle-income countries (LMICs) have not been well characterized. This is a concern because research shows an association between chronic low-dose herbicide exposure and adverse health effects. This study explored take-home herbicide residue exposure risks among forestry workers in the Western Cape, South Africa, through the community-based participatory research approach of photovoice. A key finding of the study was the absence of provisions related to take-home exposure in the national legislation and workplace policies, which largely contributed to poor adherence to risk reduction practices at worksites, in addition to workers transporting residues to their homes. This study demonstrated evidence of the key omissions regarding take-home exposure at the policy level (e.g., recommendations for employers to reduce take-home risks among employees, and training of workers and their families on take-home exposure) and take-home herbicide residue exposure among worker’s families, including children.

Herbicide residues of pre-harvest burndown in cowpea bean (Vigna unguiculata) grains

Cowpea bean (Vigna unguiculata) is usually submitted to pre-harvest burndown with herbicides aiming to an early harvest. We aimed to quantify the residues of paraquat, diquat, glufosinate-ammonium and glyphosate in cowpea grains subjected to two timings of pre-harvest burndown. Three identical experiments were installed in Dourados (Lat. 22° S), Sinop (Lat. 11° S) and Teresina (Lat. 05° S), Brazil, comprising the pre-harvest burndown of cowpea bean with these herbicides, applied either with 50 or 75% of the pods dry and ready for harvest. As hotter and drier the location as slower the herbicide dissipation. Glyphosate should not be used for pre-harvest burndown of cowpea. Herbicide residues were above the maximum levels stated by the Brazilian legislation when applied with 50% dry pods. Burndown herbicides aiming to speed harvest should be applied with at least 75% dry pods in cowpea to ensure safe herbicide residue levels in grains.

Effects of Low-Dose Applications of 2,4-D and Dicamba on Cucumber and Cantaloupe

Agronomic crops engineered with resistance to 2,4-D or dicamba have been commercialized and widely adopted throughout the United States. Due to this, increased use of these herbicides in time and space has increased damage to sensitive crops. From 2014 to 2016, cucumber and cantaloupe studies were conducted in Tifton, GA to demonstrate how auxinic herbicides (2,4-D or dicamba), herbicide rate (1/75 or 1/250 field use), and application timing (26, 16, and 7 d before harvest (DBH) of cucumber; 54, 31, and 18 DBH of cantaloupe) influenced crop injury, growth, yield, and herbicide residue accumulation in marketable fruit. Greater visual injury, reductions in vine growth, and yield loss were observed at higher rates when herbicides were applied during early-season vegetative growth compared to late-season with fruit development. Dicamba was more injurious in cucumber while cantaloupe responded similarly to both herbicides. For cucumber, total fruit number and relative weights were reduced (16 to 19%) when either herbicide was applied at the 1/75 rate 26 DBH. Cantaloupe fruit weight was also reduced 21 and 10% when either herbicide was applied at the 1/75 rate 54 or 31 DBH, respectively. Residue analysis noted applications closer to harvest were more likely to be detectable in fruit than earlier applications. In cucumber, dicamba was detected at both rates when applied 7 DBH, while in cantaloupe it was detected at both rates when applied 18 or 31 DBH in 2016 and at the 1/75 rate applied 18 or 31 DBH in 2014. Detectable amounts of 2,4-D were not observed in cucumber but were detected in cantaloupe when applied at either rate 18 or 31 DBH. While early season injury will more likely reduce cucumber or cantaloupe yields, the quantity of herbicide residue detected will be most influenced by the time interval between the off-target incident and sampling.

Landrace Maize Varieties Used as Phytoremediation of Contaminated Soil with 2,4-D + Picloram

The use of herbicides such as 2,4-D + picloram in livestock areas can contaminate and hinder the use of the production system for subsequent crops of other crops. The objective of the research was to evaluate the ability of landrace maize varieties to reduce contamination of soil treated with 2,4-D + picloram, simulating existing conditions in the Amazon Biome. The experiment consisted of 6 phytoremediation treatments (4 landrace maize varieties, 1 hybrid maize cultivar and 1 control without cultivation), 2 herbicide conditions (with and without) and 3 evaluation periods (28, 56 and 84 days). The soil was contaminated and the maize was subsequently cultivated under the herbicide conditions mentioned above. After each evaluation period, soil samples were collected, which were used to mount bioassays by growing cucumber (plants sensitive to the herbicide). Emergence, aerial dry mass and root dry mass were evaluated. All variables were affected by the herbicide residue. However, the reduction in herbicide persistence in each evaluation period was notable, resulting in the normal reestablishment of bioindicator seedlings, especially in the last evaluation at 84 days. The samples obtained in the soil cultivated with the varieties CR purple and CR white showed the best conditions for the development of cucumber, demonstrating the potential to be studied in phytoremediation programs.

Responses of spring-seeded cover crop roots by herbicide residues and short-term influence in soil aggregate stability and N cycling

Cover crop (CC) prevalence between cash crop systems is contributing to long-term sustainable crop production systems. However, herbicide residue impact on CC root growth and its subsequent effect on soil aggregation and fertility are unknown. An untreated control plus preemergence (PRE) application of saflufenacil (at 67 and 134 g a.i. ha−1)/dimethenamid-P (at 668 and 1336 g a.i. ha−1) as well as S-metolachlor (at 1600 and 3200 g a.i. ha−1)/atrazine (at 1280 and 2560 g a.i. ha−1) + mesotrione at 140 and 280 g a.i. ha−1to sweet corn (Zea mays L. var. rugosa Bonaf.) and imazethapyr (100 and 200 g a.i. ha−1) to pea (Pisum sativum L.) were made in spring 2011 and spring 2012. One year later, ryegrass (Lolium multiflorum Lam.), buckwheat (Fagopyrum esculentum Moench), sorghum–sudangrass [Sorghum bicolor (L.) Moench × S. bicolor var. sudanese (L.)], and spring wheat (Triticum aestivum L.) were seeded. Root biomass and N content, wet aggregate stability (WAS), and aggregate size plus soil mineral N (SMN) were determined. Buckwheat root biomass declined in all herbicide treatments but root N declined in imazethapyr and S-metolachlor/atrazine + mesotrione at the 2× and 1× rates, respectively. Ryegrass root biomass decreased in S-metolachlor/atrazine + mesotrione but root N content declined only at the 2× rate. Sorghum–sudangrass and spring wheat roots decreased in imazethapyr and S-metolachlor/atrazine + mesotrione at the 2× rate, respectively. Despite the impact of herbicide residues on roots, differences in aggregate size, WAS, and SMN were not detected. Findings from this study add knowledge on herbicide residue effect on CC root growth and provide useful CC seeding guidelines for growers.