Genus species: Chenopodium album, Amaranthus hybridus, Senecio vulgaris, Ambrosia artemisiifolia
Common names: Lambsquarters, Smooth Pigweed, Common Groundsel, Common Ragweed
Background and Distribution: There are currently 5 different weeds in occurring in NY that have herbicide resistant biotypes (individuals within a population). Lambsquarters (Chenopodium album), reported in 1977, was documented as having biotypes resistant to atrazine, cyanazine, and simazine herbicides. Lambsquarters is now the most widespread herbicide resistant weed in NY. Scientists estimate there are 1,950 infested sites with an estimated acreage between 10,001 and 100,000 acres. The most recently discovered weed is Common Ragweed (1993) also documented as having biotypes resistant to atrazine, cyanazine and simazine.
Crops of Concern: Corn, soybeans and crops that follow.
Potential for Economic Impact: Preplant weed management is critical to successful berry crop production. Berry crops are often planted in succession after field crops as herbicide options for berries are greatly reduced compared to those for field crops. The possibility for resistant weeds to occur in new berry plantings exists in this instance. Berry crops are also a perennial cropping system. Introduction of herbicide resistant weeds into an established planting could have significant impact on weed management options and costs.
Identification: Look for weeds that survive an herbicide application. Before assuming this is due to resistance development, rule out factors that affect herbicide efficacy such as problems in application, improper application timing, unfavorable weather conditions, and weed flushes after application of a non-residual herbicide. Then ask the following questions: 1. Are other weeds listed on the product label controlled satisfactorily apart from the one remaining? 2. Did the same herbicide or another herbicide with the same mode of action fail in the same area of the field in previous years? 3. Was there extensive use of the same herbicide or herbicide mode of action year after year?
Monitoring and Management: Weed identification and mapping in plantings may help to identify herbicide resistant populations before they become well established.
- Cultural Management – Rotate crops. Plowing, disking, cultivating, mowing, hoeing, and hand pulling to reduce weed populations before they go to seed; spring and fall moldboard plowing to bury weed seed deeply after its shed.
- Chemical Management – Rotate herbicides and herbicide classes or families. Use herbicides with shorter residuals. Use effective herbicide mixtures from more than one class. See listings under specific crops in the Cornell Pest Management Guidelines for Berry Crops.
Additional Resources:
- Herbicide Resistant Weeds – University of Minnesota
State contact: Dr. Russell Hahn, Extension Faculty, Weed Science
Cornell University, Department of Crop and Soil Sciences
238A Emerson Hall – CSS, Ithaca, 14853, New York
Phone : (607) 255-1759 e-mail rrh4@cornell.edu