History of herbicide
Download the War on Weeds game and play along as you gather ideas on how to manage your weeds.
1. 2,4-D debuts in 1946. This broadleaf killer kicks off the row-crop herbicide era. It amazes wide-eyed farmers with its activity on broadleaves, but it has a nasty drawback – drift. Several generations of farmers and their spouses get used to covering tomato plants when it's applied to nearby fields.
2. Resistance tip: Be competitive. “Maintaining crop competition and avoiding skips will prevent weeds from getting a foothold,” says Matt Liebman, Iowa State University (ISU) agronomist. This step is still as applicable today as it was back in the 1940s to farmers who just had 2,4-D to use.
3. Atrazine debuts in 1958. This popular corn herbicide controls a number of broadleaves and grasses. The photosynthesis-inhibitor mode of action that includes atrazine will be joined in the 1960s by microtuble inhibitors (trifluralin) and shoot inhibitors (Lasso).
4. Resistance tip: Rotate crops. Like back in the 1950s and 1960s, crop rotation remains a weed-control tool. A multiyear ISU study examined a corn-soybean rotation and showed inclusion of these crops with small grain and legumes in three- and four-year rotations effectively suppressed weeds. “This was despite backing off herbicides in the three- and four-year systems,” says Liebman.
5. Weed scientists confirm a common groundsel biotype resistant to atrazine's mode of action in Washington in 1970. Over time, more weeds develop resistance. Fortunately, weed resistance to atrazine doesn't deter its use. Atrazine is contained in over 60% of corn herbicides today.
6. Seven herbicide modes of action for corn and soybeans debut during the Golden Age of Herbicides from 1970 to 1989.
● GS inhibitors: (glufosinate, contained in Liberty)
● EPSP inhibitors: (glyphosate)
● ACCase inhibitors: (fenoxaprop, included in Fusion)
● HPPD inhibitors: (Isoxaflutole, contained in Balance that was later commercialized in 1999)
● PPO inhibitors: (Lactofen, contained in Cobra)
● ALS inhibitors: (Imazethapyr, contained in Pursuit)
● Carotenoid Synthesis inhibitors: (Norflurazon, contained in Zorial)
7. Resistance tip: Cultivate rough spots. Think you can dig your cultivator out from the back of your machine shed or tree claim? Well, it can still play a role in ridding your fields of herbicide-resistant weeds.
“The lion's share of weed control will still come from herbicides,” says Mike Owen, ISU Extension weed scientist. However, cultivating those areas with hard-to-control weeds can help manage them and prevent them from going to seed.
8. Roundup Ready debuts in soybeans in 1996. This nonselective herbicide technology enables glyphosate to blanket the crop while obliterating nearly all weeds. Previously to the development of glyphosate-tolerant systems, glyphosate is used as a burndown at an 8- to 10-ounce-per-acre rate. Supplemented with 2,4-D, its cost covers $90 to $100 per gallon, says Owen. “In 1996, glyphosate was used in an entirely different manner on entirely different suites of weeds,” says Owen. In essence, Roundup Ready dumbs down weed control, breaking it down to one and later two postemergence applications of just glyphosate. It soon catches on with corn, too. With weed-control worries over, Roundup Ready frees up considerable time for farmers to take on more land or to take a summer vacation.