Volunteer Potatoes: The Weed You Didn’t Expect
Volunteer potatoes, an unexpected yet persistent problem in rotational farming systems, arise when unharvested potato tubers survive in the soil. These tubers sprout new plants, competing with subsequent crops for sunlight, water, and nutrients. Beyond competition, volunteer potatoes harbor pests and diseases that threaten neighboring fields, complicating pest management strategies and reducing overall crop yields.
The persistence of volunteer potatoes has been documented across potato-growing regions, with Michigan providing a notable case study. Warm winters, high potato production intensity, and limited effective control options exacerbate the issue.
The Risks of Volunteer Potatoes
A Reservoir for Pests and Diseases
Volunteer potatoes serve as an overwintering site for pests like the Colorado potato beetle. These beetles feed on the volunteers in spring and migrate to production fields in summer, causing waves of infestation. Late blight, a devastating potato disease, also originates from volunteer tubers under warm winter conditions. These challenges increase the complexity and cost of pest and disease management.
Survival Conditions: Temperature and Depth
Volunteer potatoes’ survival depends on their depth in the soil and the severity of winter frost. Tubers buried deeper than four inches are insulated from freezing temperatures, while those near the surface face a greater likelihood of exposure to the threshold of 50 frost-hours at or below 28°F. Data from Michigan State University’s Enviroweather program shows that most winters in Michigan since 1999 have been warm enough for significant volunteer potato survival, particularly in regions with intense potato production like Montcalm and St. Joseph counties.
Strategies for Managing Volunteer Potatoes
Chemical Control and Herbicide Efficacy
Volunteer potatoes are notoriously resistant to control, as no single herbicide guarantees complete eradication or prevents the production of new daughter tubers. Recent studies by Michigan State University tested combinations of herbicides and found that:
- Adding atrazine to herbicide treatments significantly reduced daughter tuber production.
- Early application, when volunteer plants are under six inches tall, yields the best results, reducing tuber production by over 90%.
- Tank-mixing herbicides with insecticides reduced Colorado potato beetle populations by an average of 94% without harming the main crop.
Control Recommendations by Crop
Control measures vary by rotational crop. Effective options include:
- Corn: Callisto, Armezon, paired with atrazine.
- Winter Wheat: Group 4 (e.g., 2,4-D, dicamba) and Group 27 (e.g., Huskie).
- Soybean: Reflex, Raptor, and glyphosate (depending on crop traits).
- Alfalfa: Pursuit, Raptor, and 2,4-DB.
- Sugarbeet: Nortron and Stinger.
Preventative measures, such as thorough harvesting to minimize leftover tubers, remain critical in reducing volunteer emergence.
Volunteer potatoes represent a dual threat: reduced crop yields due to competition and the perpetuation of pests and diseases. While chemical controls and early interventions offer partial solutions, farmers in high-risk areas must adopt integrated management strategies to address this persistent problem. Combining cultural practices, precise herbicide applications, and pest monitoring can mitigate the impacts of volunteer potatoes and protect crop profitability.
