Herbicide

– **History**
– Cultural controls were used prior to herbicides for weed control.
– Mechanical methods like tillage and flooding were also used.
– Inorganic chemicals were used in the late 19th and early 20th centuries.
– Herbicides revolutionized weed control during the Second World War.
– The discovery of 2,4-D marked a significant breakthrough.

– **First Herbicides**
– 2,4-D was the first selective chemical herbicide.
– Major breakthroughs in herbicides occurred during World War II.
– 2,4-D was synthesized by W. G. Templeman and R. Pokorny.
– Juda Hirsch Quastel’s team also discovered effective herbicides.
– 2,4-D’s commercial release in 1946 revolutionized agriculture.

– **Further Discoveries**
– Triazine herbicides like atrazine were introduced in the 1950s.
– Triazines are a major concern for groundwater contamination.
– Atrazine has a long persistence in soil, especially under alkaline conditions.
– Herbicide formulations have evolved with different compounds.
– Continued research aims to develop safer and more effective herbicides.

– **Herbicide Usage**
– Herbicides are primarily used in agriculture.
– In the US in 2012, 91% of herbicide usage was in agriculture.
– Worldwide pesticide expenditures in 2012 were significant.
– Herbicides constituted the largest portion of pesticide sales.
– Herbicides are also utilized in forestry and pasture systems.

– **Effect on Crop Yields**
– Herbicides, along with fertilizers and improved cultivars, have boosted crop yields significantly.
– Yields of major crops increased by 3x to 6x from 1900 to 2000.
– Selective herbicides target specific weed species.
– Non-selective herbicides kill plants indiscriminately.
– Herbicides play a crucial role in modern agriculture for weed management.