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Ask An Entomologist @BugQuestions
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With Glyphosate being in the news due to a recent court ruling, let's take this opportunity to explore the history of pest control in this week's #DeepDive.

It's a huge and complex topic, so the best we can do is a brief overview.
It's not really known when humans started using pesticides.

The first agricultural societies began about 10,000 BCE, with several independent shifts around the world from relatively nomadic lifestyles to those tending crops.
The first records of pesticides being used is in Sumeria, where they used elemental sulfur to control crop pests.

This is largely an accident of geography; Sulfur deposits are abundant in a stretch between Mosul and Fatha...which allowed easy access.
Over in China, one plant used historically for pesticide use was the Chinaberry tree...which we know contains a lot of different toxins. It was mainly used for household pests, although there was some use in agriculture.
In India, the Neem tree was also used quite a bit in traditional medicine...and a few thousand years later, it was found that Azadirachtin was the active ingredient.
So, the earliest attempts at pest control that we're aware of all revolved around using what was found in the area that seemed to kill bugs well.

These were either natural minerals or plants which had been used in medicine.

Sometimes these worked, sometimes they didn't.
As agriculture grew, farmers became more inventive...although exact dates are hard to come by.

Later developments included the use of ash as a repellent/suffocant, sulfur fumigation, and use of oil to keep insects from laying eggs.
One of the most sophisticated pest control techniques of the ancient world wasn't chemical-it was biological!

Around 300 BCE, the Chinese were using weaver ants to control caterpillars and beetles which attacked Citrus crops!

In ancient Rome, we see this pattern continue. Many authors (including Aristotle) valued aromatic plants for their pest control qualities, and Pliny the Elder even recommended what appears to be an attempt at vinegar fumigation.
About 800 BCE, we start seeing sophisticated storage methods.

Grain was often kept in huge pits, and people started developing techniques to reduce moisture and oxygen to prevent insect and fungal growth.

So even back then, we were on top of things.
Another thing folks figured out about this time was that you could separate out insect pests from the seeds by letting the infested grains float up.

This method is still used by some cultures today, although methods are more complex.

From here on out, it's a bit of a grey area. We know that pest control developed, and there's even some discussion of arsenic compounds being used in the middle ages...but there's not a lot of information I could find.
So...a lot of pest control techniques were developed very early, and pest control looked the same until the late 1800s.

During the 1700s and the 1800s, there was a rapid change in agriculture from a subsistence lifestyle to a more commercial business enterprise.
At the same time, the game was changing. We had taken a lot of crops out of their home ranges, and pests had adapted to feed on them.

In essence, we accidentally domesticated *a lot* of bugs.…
Around this time, we see the development of a lot of insecticides using arsenic. We'd known that arsenic containing dyes-usually green ones-were toxic to people, so we started using them to combat insects.
Around this time, we also started to develop the tools to make spraying for pests easier.

If you're familiar with old-timey cartoons, you may recognize this. This is one of the first widely available pesticide sprayers which were used on farms.
After this, we start to see a rapid development of pesticides...and the period of 1920-1970 should really have it's own thread.

DDT was the biggest leap in this era, and it's super important because it was practically non-toxic.…
However, there was some environmental damage which occurred because of widespread applications. Rachel Carson discussed this very widely in Silent Spring.…
Again, this needs its own thread to properly discuss, but Silent Spring was another turning point for pest control.

Yes, Carson got some stuff wrong. Yes, banning DDT was somewhat political.

DDT use was already declining due to increased pest resistance.…

This also popularized the idea of 'least use' approaches to pest management, and the idea that we should treat only when farmers will lose revenue due to losses by pests.
As time goes on, we see techniques get ever more sophisticated.

Starting in the 1910s, we start seeing the development of Bacillus thuringiensis as a pest control product. China and Brazil start developing viral pesticides.
In the 1990s, for the first time, we start seeing transgenic crops...and this brings yet another new era.

It's recognized that these crops can be fairly specific, and we can find and use highly specific proteins.

We also start caring about management of resistance to pcides.
See, by now, we've been watching all sorts of bugs get resistant to insecticides. So much so that one species-the Colorado Potato Beetle-has become a symbol of political resistance.

...and that's where pest control's going in the future.

Resistance is a big issue, and techniques are being developed to combat it.

Development may be slowing down. This is somewhat in part to regulation, but also because companies want to make less toxic pesticides.

So they're a bit more choosy nowadays.
Between 1995 and 2014, the number of compounds companies went through to find a successful product nearly tripled from about 50,000 (1995) to 150,000 (2014).

In addition, costs also increased greatly.

Automation, and enhanced high-throughput screening techniques will help.
If you're curious about the economics of the industry, the below is a great place to start.

So...pest control has changed a lot over the years.

It's gone from using local plants and minerals, to a process which screens hundreds of thousands of compounds to find a single product.

It's also going to change in the future, especially with the advent of robotics and AI.
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