Herbicide Injury in Hemp

Printer-friendly .pdf version of this page

Lynn M. Sosnoskie and Elizabeth C. Maloney
Contact: lms438@cornell.edu, 315-787-2231

Previous research conducted at Cornell AgriTech has found hemp to be sensitive to several pre- and post-emergence herbicides. In the absence of registered products, owners who experience herbicide injury may be seeing damage resulting from residue carryover in the soil or drift from neighboring crops. The images included in this handout document symptoms observed from foliar applications with products that are representative of several herbicide classes.

Note: Herbicide symptomology can be affected by many factors, including variety and environmental conditions. Many herbicides may have similar symptomology (such as stunting). Herbicide injury may also be confused with pathogen infections, stress responses, insect damage, nutrient deficiencies.

WSSA 2. ALS-inhibiting herbicides. Chlorosis (yellowing), purpling of tissue or just veins.
WSSA 2. ALS-inhibiting herbicides. Chlorosis (yellowing), purpling of tissue or just veins. Low doses may result in leaf distortions or deformations that could mimic auxin damage.
EPSPS-inhibiting herbicide. hlorosis starting at the base of leaves, witchesbrooming, stunting.
WSSA 9. EPSPS-inhibiting herbicide. Glyphosate is the only registered herbicide in the group. Chlorosis starting at the base of leaves, witchesbrooming, stunting.
Auxin mimics. Characterized by leaf and stem distortions such as twisting, strapping, puckering, cupping, curling, rolling
WSSA 4. Auxin mimics.Characterized by leaf and stem distortions such as twisting, strapping, puckering, cupping, curling, rolling. Auxinic herbicides are active at very low doses.
HPPD-inhibiting herbicides. Characterized by bleaching/whitening of tissue which turns necrotic and burns away.
WSSA 27. HPPD-inhibiting herbicides. Characterized by bleaching/whitening of tissue which turns necrotic and burns away. WSSA 13 herbicides may look similar.
PS II-inhibiting herbicides. Water-soaking that starts at the edges of leaves becoming interveinal (between veins) chlorosis and then necrosis.
WSSA 5, 6. PS II-inhibiting herbicides. Water-soaking that starts at the edges of leaves becoming interveinal (between veins) chlorosis and then necrosis.

WSSA 14 . Necrotic spots or lesions. Purpling of tissue may occur

WSSA 14 (above) and 10 (below). PPO-inhibiting and nitrogen metabolism inhibiting herbicides, respectively. Necrotic spots or lesions. Purpling of tissue may occur with WSSA 14. Some spots can be white. WSSA 22 can show similar symptoms.

WSSA 10 nitrogen metabolism inhibiting herbicides, respectively. Necrotic spots or lesions

Author: cdc25

Craig Cramer is a communications specialist, in the School of Integrative Plant Science, College of Agricultur and Life Sciences, Cornell University, Ithaca, N.Y.