Project Overview

Reports

Commodities

• Agronomic: peanuts

Target Pests

Practices

• Pest Management: chemical control, cultivation, cultural control, mechanical control, mulches - general, pesticide resistance management, prevention, temperature treatment,

• Crop Production: conservation tillage, cover crops, cropping systems, no-till

Palmer amaranth (Amaranthus palmeri) is a very damaging weed in row crops, especially peanuts, in the United States. As a C4 plant it has high water use and photosynthesis efficiency, it can grow 1 inch a day under optimal conditions. A healthy female plant can produce up to half a million seeds within 2-3 months of growth, which is a very significant amount for an annual plant. Many peanut growers in the southeast US struggle to control this weed using herbicides, due to multiple resistance against several modes of action. In the last several years, glyphosate, ALS and PPO-resistant Palmer has widely spread in mid-south and Mississippi delta area (account for over 80% of all the Palmer populations in this area). Once this multiple herbicide resistant Palmer spreads to the major US peanut production area, which produces 80% of all US peanuts, (south AL, FL panhandle and southern GA) it will be nearly impossible to control it by herbicides alone. Some peanut growers in northeast AR and southeast MO have resorted to abusing paraquat by spraying additional applications to control this specific type of resistant palmer, this is a highly toxic postemergence herbicide, risking their health and peanut yield (paraquat is very injurious to established peanut plants beyond 30 days after planting). To prevent this illegal practice being adopted in southeast major peanut production areas, evaluation of ALS and PPO-resistant Palmer control methods using integrated and non-chemical approaches is urgently needed.

In this project, the project team proposes to established multiple field and greenhouse experiments to study: 1) evaluate integrated control methods of PPO and ALS resistant Palmer with high residue cover crop, tillage, cultivation, mowing, agronomic practices such as planting pattern and seeding rate, wickbar, and soil herbicides, 2) evaluate Palmer stump winter survival rate in no-till system, which is gaining more popularity in peanut producing area, 3) survey current herbicide resistance in Palmer populations and monitor PPO-resistance spread in AL with field survey and Palmer seedhead collection from multiple peanut fields. Field experiments will be conducted in Alabama, on agricultural research stations with heavy Palmer infestations. Resistance survey will be conducted in a greenhouse screening after seeds have been collected from multiple peanut fields throughout the state.

Project team will conduct experiments and generate effective Palmer control programs using integrated methods and non-chemical based approaches. These IPM programs can significantly reduce paraquat abuse and over-reliance on chemicals to control Palmer. They will slow down the resistance evolution and spread of PPO-resistant Palmer to peanut producing area as well. Project team will promote project recommendations through multiple peanut production meetings, AL-FL peanut tradeshow, Southeast peanut producer conference, AL auxin training and multiple experiment station field days. Future funding will be secured from USDA-NIFA, SARE, state production programs, and peanut industry to carry on field research, resistance survey and program promotion to growers. Project director will also survey peanut growers for program impact in 2021 and beyond during extension events, farm visits, emails and online surveys. Reduction of paraquat abuse and spread of PPO-resistant Palmer into peanut production area will also be documented through surveys. Expected short and long term impact will include increased awareness and knowledge based about the risk of PPO-resistant and multiple resistant Palmer amaranth, increased knowledge regarding Palmer control with non-chemical based approaches, willingness to adopt IPM approaches to control Palmer, satisfactory rating of adopted IPM programs promoted by this project, increase profitability, cost per acre saving for weed control, etc.

Project Output:

1.Conduct two field experiments at two locations (Headland and Fairhope AL) to evaluate how cover crop residue, planting pattern, seeding rate, mechanical cultivation, soil herbicides and wick bar can be integrated into effective, economical and sustainable PPO-resistant Palmer management strategy in peanut. Conduct a greenhouse experiment on campus to evaluate Palmer stump/root survivability after cold treatments (-5C, 0C and 5C) for various length of time. Palmer stumps will be dug from various peanut fields in south Alabama before harvest.

Collect data regarding Palmer density, height, peanut canopy width and height, Palmer control rating, # of seed produced, and peanut yield from field experiments. Collect CO₂ assimilation rate, quantum yield, stomata conductance and other physiological data to measure Palmer stump and shoot vigor following cold treatments in greenhouse experiments.

Conduct a weed resistance survey in major peanut production counties in AL. Sample Palmer amaranth seedheads from highly infested fields and screen these populations for herbicide resistance in greenhouse on Auburn campus. The goal is to expand the current Palmer resistance database in AL by screening 15 additional fields in peanut producing counties.

2. Promote project findings and recommendations to peanut growers in the southeast US through AL peanut production meeting series (7-8 meetings throughout the state), AL-FL peanut tradeshow (Dothan AL), Southeast peanut grower conference (for MS, AL, GA and FL growers at Panama city FL), AL-GA crop consultant annual conference, Wiregrass REC annual field day (mid-August), Wiregrass weed control tour (mid-July), Central AL row crop tour (late-July), UFL extension peanut field day (Marianna FL, late-August), southeastern peanut farmer magazine (hosted by National Peanut Board), Alabama IPM newsletter, Southeast farm press, Agfax, American Peanut Research and Education Society annual conference, Southern Weed Science Society annual conference, and Alabama extension auxin training (mandatory training for most cotton and peanut growers), etc. The goal is to cover 50-80% of the peanut growers with project information in the tri-state area where 80% of the US peanut is produced in the next 2-3 years.

3. Leverage funding from USDA-NIFA CPPM program, commodity groups, state funding for production agriculture, and peanut industry. Continue grower survey to document adoption rate, effectiveness of recommended control program, new infestation, peanut yield, profitability and $ saving per acre, etc. Publish data and results obtained from this project in Weed Science or another peer-review SCI journal (may require repeating the experiment in 2021 to meet publication requirement). Continue monitoring the spread of PPO-resistant Palmer amaranth through field survey.

Project anticipated outcomes:

1.Develop effective, economical and sustainable Palmer amaranth management program and new control options to peanut producers in the southeast. Control PPO-resistant Palmer amaranth effectively with less reliance on chemical control and foliar herbicides, particularly paraquat which is very toxic to human. Develop a management strategy to address this problem to prevent crop competition and yield loss. Determine if Palmer stump can survive warm winter in the major peanut production area in deep south, and if these stumps can produce shoots earlier than when seedlings start to appear in field.

2.Increase understanding of current herbicide resistance level in Palmer amaranth populations in major peanut growing areas. Slow down the spread of PPO resistance in Palmer amaranth to major peanut production area in south AL, FL panhandle and south GA. Increase knowledge of controlling herbicide resistant Palmer amaranth in peanut. Increase growers’ awareness of Palmer resistance evolution and the urgent needs to adopt IPM to manage Palmer in peanut. Increase grower adoption of IPM practices that have been proven effective in this project.Reduce paraquat abuse and potential risk to pesticide applicators due to its acute toxicity to mammal.