Root Collar Excavation – ARR Solutions

The fungus is present in most orchards, and can survive in soil for decades, waiting for a suitable host tree. Once one tree is infected, the fungus moves underground through root-to-root contact to neighboring trees, forming infection islands or clusters. Peach trees are particularly susceptible, with even the healthiest trees succumbing to the disease in infection clusters. To keep our future peachy, solutions are desperately needed.

Scientists from Clemson University have been developing much-needed methods to combat Armillaria root rot. Across many studies spanning over a decade, Dr Guido Schnabel and his colleagues have shown that planting trees on berms and removing the soil around the upper portion of a tree’s roots – called root collar excavation – can effectively slow disease progression.

Root collar excavation prevents the pathogen from reaching the trunk. It works because the fungus cannot survive the extreme temperatures in the exposed roots. By confining the disease to the affected roots, tree death can be delayed by an average of two years. However, the root collar excavation technique is limited by several factors. Excavating around tree roots can be difficult and labor-intensive, and removal of the berm between trees in a row also poses challenges.  

Continuous berms between trees in a row can interfere with tree care and fruit harvest due to the uneven ground around the trees. Dr. Schnabel and Dr. Bulent Koc addressed these limitations by developing a mechanized method to remove the soil between each tree in a row.

Inspired by street sweepers, the researchers designed a rotating, horizontal paddle wheel attached to a tractor that removes berms mechanically. Removal of the soil between trees will also facilitate the excavation process around the tree roots.

The team’s methods slow tree-decline without reducing fruit yields, while also minimizing labor costs. Most importantly, they might just give peaches a chance. And that’s good news for consumers!