According to a survey of weed scientists, Palmer amaranth (Amaranthus palmer S. Wats.) and Waterhemp (Amaranthus tuberculatus (Moq.) Sauer) are two of the most common/troublesome weeds of grass crops, broadleaf crops, fruits and vegetables in the US, particularly in the Southeast, Midsouth and Midwest. Both are highly aggressive species due in part to their large sizes, prodigious seed production and the evolution of herbicide resistance. Infestations can reduce yields through direct competition, by interfering with the deposition of crop protection chemicals, and by physically impeding the movement of men/machinery at harvest. Palmer amaranth andwaterhemp are also resistant to multiple herbicide sites of action (acetolactate synthase (ALS)-, microtubule-, photosystem II (PSII)-, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS)-, protoporphyrinogen oxidase (PPO)-, long chain fatty acid (LCFA)- and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitors and the synthetic auxins) which can significantly impact management success. Palmer amaranth and waterhemp are present in New York, although both are not yet widely distributed. Discussions with NYS-IPM/CCE/regional weed scientists suggest that Palmer amaranth and waterhemp populations in the Mid-Atlantic/Northeast are likelyThe ultimate goal of this project is to develop Palmer amaranth and waterhemp control strategies that acknowledge current resistance issues and address how variability in both current and future production environments can affect weed control success.The objectives include:1. Documenting the current distribution of Palmer amaranth and waterhemp throughout New York state and in relation to geographical, environmental, and crop production parameters.2. Collecting seed from Palmer amaranth and waterhemp populations and screening for resistance to commonly applied herbicides and herbicide classes.3. Describing the germination and emergence phenology, growth, competitiveness, reproductive output, and herbicide sensitivity of Palmer amaranth and waterhemp under a range of temperature and soil moisture conditions that can/will impact New York agroecosystems.