As you drive through the Central Sands in August, it’s not unusual to see brown and wilted spots in those potato fields that were so lush in July. What causes potato crops that once looked so good to suddenly turn brown? Ironically, it is the same problem that many homeowners have in their gardens. It’s called potato early dying, and it results when two common soil inhabitants get together to prevent plants from taking in and transporting the nutrients needed for growth.
The two soil dwellers are a fungus and a nematode. The fungal disease attacks roots and stems, blocking the cells that move nutrients. The microscopic nematode, which is invisible to the human eye, feeds on root hairs making it easier for the fungus to enter the plant. Mid-season conditions, such as heat and dry areas in fields, stress the rapidly growing plants in August; the seemingly innocuous critters then get together and stop the plant’s growth in its tracks at the very time when the plant is putting all its energies into enlarging its tubers. Soil survey results show that the majority of Wisconsin’s potato fields and many home gardens are routinely infested by both the nematode and fungus; without proper management, plant growth can be reduced by 60% and result in potato yield losses of 20-50%. Unfortunately, the only consistently effective management technique is chemical fumigation. (more…)