No farmer deals with just one weed in his or her fields, but every farmer has a “worst weed” that causes the most trouble. Farm Journal Media surveyed more than 1,000 farmers in 2013 and again in 2015 to find out what that worst weed was.
And although palmer amaranth tends to grab the lion’s share of headlines in agricultural media, another weed is king according to farmers – waterhemp.
In 2013, farmers ranked waterhemp as their number one significant weed problem (30%), followed by marestail (16%), marestail (16%), “other” (12%), palmer amaranth (11%) and grass species (9%). For 2015, the rankings looked largely the same, with waterhemp grabbing a commanding lead again (35%), followed by marestail (19%), ragweed (14%), palmer amaranth (13%), “other” (11%) and grass species (8%).
Waterhemp and palmer amaranth are both categorized as pigweed species, notes Aaron Hager, associate professor of weed science with the University of Illinois.
“Accurate identification of weedy Amaranthus species during early vegetative species can be difficult because many exhibit similar morphological characteristics – [in other words], they look very much alike,” he says.
Just like its palmer amaranth cousin, waterhemp can grow fast and produces prolific amounts of seed. According to the United Soybean Board, waterhemp can produce 1.5x more seeds than most other pigweed species. That means a single plant can produce 250,000 to 1 million seeds in optimal conditions. The USB notes that these seeds can remain viable in the soil for several years – as much as 12% of waterhemp seeds can germinate after four years.
The USB encourages a multi-step approach to waterhemp control that includes:
- Apply an effective pre-emergent soil-residual herbicide.
- Overlap post-emergent residual herbicides when weeds are no bigger than 3” to 4”.
- Scout seven to 14 days after herbicide applications to verify effectiveness.
If weeds reach germination, expect to wage war on waterhemp again next year.