5E: Do You Know Archive

Do You Know?

Test your knowledge of herbicides, weed resistance, and human health impacts of pesticide exposure!  See the Do You Know questions and answers below.

What percent of birth defects are observable by doctors while a newborn is still in the hospital or birth center?


About two-thirds, and the percent is likely falling. In the Garry et al. (2002) study of herbicide-induced birth defects in the Red River Valley, medical records and birth certificates accounted for only 60% of total birth defects at the end of a child’s first year of life. About one-third were diagnosed at three years of age or older.

The percent of total birth defects diagnosed later in life is likely rising as a result of trends in autism, ADHD, and a host of other neurological and reproductive system birth defects.

Access state-specific birth defect registries supported by the CDC.

Historically, what is the most widely used pesticide ever in both the U.S. and globally?


Measured by pounds of active ingredient applied in any given year, glyphosate herbicide (aka Roundup) has been for a decade now the most heavily applied pesticide ever (for the details, see Benbrook, 2016a).

The introduction of genetically engineered, herbicide-resistant corn, soybeans, cotton, and canola dramatically increased glyphosate use from 1996 to 2006. The rate of increase has slowed in recent years, and overall use may have peaked in 2016.

Two Part Question:

#1. In the 1980s through the mid-1990s, what forces or institutions played the biggest role in driving change in corn and soybean weed management systems?

#2. In the decade ahead, what forces or institutions will likely play the biggest role in driving change in corn and soybean weed management systems?


Part 1:

In the 1980s through the mid-1990s, the three major drivers of change in corn and soybean weed management were:

  1. The herbicide-biotechnology-seed industry.
  2. Farmers looking for simpler, more effective solutions to tough weed control challenges.
  3. University weed management scientists and extension specialists.

Part 2:

In the decade ahead, the three major drivers of change in corn and soybean weed management are likely to be:

  1. Consumers and citizens worried about the collateral damage stemming from more intensive herbicide use.
  2. Food companies, through supply-chain interventions.
  3. Farmers choosing to reduce reliance on herbicides by adoption of multi-tactic, “many little hammer” weed management systems.

Which two corn and soybean herbicides will account for most of the increases in the next 5-10 years in overall herbicide use and risks across the Midwest?


2,4-D and dicamba, because of recently approved genetically engineered corn and soybean varieties resistant to these herbicides, as well as combinations of glyphosate, glufosinate, and the “fop” herbicides.

By 2020 according to Monsanto and Dow AgroSciences, most conventional corn and soybean seed will carry either the 2,4-D or dicamba resistant trait, increasing the combined use of these two relatively high-risk herbicides on these two crops by around 30-fold compared to 2010.

Before the widespread planting of genetically engineered, herbicide-resistant corn and soybeans in the Midwest, which birth defect was linked to glyphosate (Roundup) herbicide use?


ADHD (Garry et al., 2002b)

Why are physicians and risk assessment scientists so concerned over the impact of newly approved, 2-4-D and dicamba resistant corn and soybean varieties?


Four primary reasons:

  1. Dramatic increases in the acres planted to these new GE-HR varieties, and sprayed with these two herbicides.
  2. Much higher average rates of application and more applications per acre.
  3. The much longer time period over which herbicides will be sprayed (~4 months instead of 1.5), increasing the number of conceptions and pregnancies that will coincide with the heavy herbicide spray season.
  4. Substantial evidence from past research and animal studies that 2,4-D and dicamba exposures can trigger adverse birth outcomes and a host of health problems later in life.

For the three major herbicides (glyphosate, 2,4-D, dicamba) that will dominate use in the coming decade on GE herbicide-resistant corn and soybean fields, in which decade was most of the toxicology studies carried out that support EPA’s evaluation of each herbicide’s toxicity to humans?


The 1980s.

This is one key reason why scientists have recently called for a thorough re-assessment of glyphosate’s mammalian toxicity (see Vandenberg et al., 2017 or Myers et al., 2016).