Deep Root Zone Affects Probability of Oak Wilt Breakouts in Central Texas

Abstract Oak wilt, caused by Bretziella fagacearum , is a significant threat to oak trees in Texas. The pathogen can be spread by underground root grafting of trees, and this means of transmission is the most effective and damaging means of spread for the live oak ( Quercus fusiformis and Q. virginiana ) mottes in central Texas. Trenches are created between disease centers and healthy trees in the hope to sever or disrupt root connections to limit the spread of the pathogen. This study subsampled 275 from a total dataset of 2,124 installed trenches to evaluate the effect of soil factors, specifically root zone depth and particle size, on the probability of trench breakouts in central Texas. Pathogen transmission breakout data created from 1990 to 2020 under the Texas Oak Wilt Suppression Project cost-share was used to determine if soil particle size and/or rooting depth could predict the success or failure of trenching in slowing the spread. Our results showed that for the subsampled trenches, the overall breakout of oak wilt was 39% compared to a 19% measured breakout for the entire dataset. Root zone depth and soil particle size significantly influenced breakout likelihood. Deeper root depth was associated with a higher probability of trench breakouts, particularly in clayey soils, while finer and silty soils demonstrated a lower risk. The findings highlight the importance of considering soil characteristics when implementing trenching strategies to control oak wilt spread. This study is the first to explore soil-related factors affecting oak wilt management in Texas and suggests that additional environmental variables could further improve predictive models of trench success.