Pigweed identification

Developed by Lynn M. Sosnoskie, Assistant Professor, Specialty Crop Weed Science Lab, Cornell AgriTech
Horticulture Section, School of Integrative Plant Science, College of Agriculture and Life Sciences, Cornell Univ.
Email: lms438 [at] cornell.edu (lms438[at]cornell[dot]edu) | Twitter: @vegfruitweedsci | Instagram: @specialtycropweedscience

Funding generously provided by the New York Corn & Soybean Growers Association (NYCSGA - 2021 Corn Research and Education Grant)

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Why ID pigweeds?

Why ID pigweeds?

Competition and yield loss

Pigweeds are some of the most commonly occurring and troublesome weeds that US growers encounter. Several pigweed species can grow very quickly, often overtaking the crops that they emerge with (like Palmer amaranth on left).


Why pigweeds?

Seed production and seedbank growth

Pigweeds can produce a lot of seed. Under optimal growing conditions, these species can produce tens to hundreds of thousands of seeds; female Palmer amaranth plants have been reported as producing up to a million seed. This leads to the development of large seedbanks.

Why pigweeds?

Herbicide resistance

As of December 2021, there are 162 confirmed cases of resistance across all pigweed species, herbicides, and states in the US. 40 of these reports detail resistances to multiple  herbicide groups within a single plant population (weedscience.org).

palmer amaranth competing with corn
waterhemp seeds
Glyphosate-resistant waterhemp