From Lynn M. Sosnoskie, Assistant Professor of Weed Management in Specialty Crops
School of Integrative Plant Science, Horticulture Section, Cornell AgriTech
Weeds have been a significant concern for hemp producers; the lack of conventional herbicides has limited the numbers of tools available for weed management relative to agronomic and many specialty crops. On 12 June, 2023, the NYS DEC accepted a supplemental label for Sonalan® HFP use on hemp (which expires on 1 May, 2026). Applicants must have the supplemental label when applying the product. When using a supplemental label, all applicable directions, restrictions, and precautions on the container label must be followed.
Ethalfluralin is the active ingredient (ai) in Sonalan® HFP Herbicide; ethalfluralin is primarily effective for the management of annual grasses (such as crabgrasses, foxtails, and barnyardgrass), although some annual broadleaf weeds (such as pigweeds, nightshades, and lambsquarters) are also susceptible to control. Sonalan® HFP can be applied to the soil surface before or after planting (but before hemp has emerged) at rates ranging from 1.5 to 3 pt/A (0.5625 to 1.125 lb ai/A). Application rates are dependent on soil type; use the lower labeled rate on coarse soils. Sonalan® HFP is limited to one application per year. The product must be incorporated mechanically or with irrigation. Poor incorporation will result in erratic weed control. The product can be used in both directed seeded and transplanted crops.
Ethalfluralin has not been tested on all hemp varieties, nor on all soil types, and it is recommended that growers make applications to small areas to ensure crop safety. Adverse edaphic and environmental conditions, such as cloddy or flooded fields, can enhance crop injury potential. Uneven application and/or incorporation can also increase the chance of crop injury. Ethalfluralin is a WSSA 3 (microtubule inhibitor) herbicide same as pendimethalin and trifluralin; injury symptoms can include stubby roots, swollen stem bases, and stunted plants. See the NYS DEC Bureau of Pesticides Management – Information Portal (NYSPAD) for a copy of the supplemental label. More information about Sonalan® HFP and contact information for sales representatives, can be found at the Gowan USA website.
