When a crop is finished, the plant matter that remains (i.e., crop residue) is incorporated into the soil. How this is done, and its effect on root diseases, are of great interest. This is true for strawberries and any other annual crop grown in open fields. Maybe we can learn something from a 15-year study on a wheat-corn rotation as it relates to wheat crown rot caused by Fusarium pseudograminearum.

Study Findings

The study by Zhou et al. (2025) looked at corn crop residue soil incorporation methods and their effect on wheat crown rot. The researchers used the same cropping pattern for 15 years. Corn harvest in mid-September was followed by three crop residue incorporation methods: “deep plowing”, “rotary tillage” and “deep loosening”. Figures 1–3 show the photos the authors used to explain these three crop residue incorporation methods. This was followed by planting wheat in mid-October. Crown rot severity was rated during the grain filling stage in May.

They found that crown rot incidence was 22% for deep plowing, 64% for rotary tillage and 49% for deep loosening. Disease severity followed a similar pattern: 7%, 24% and 19%, respectively.

The authors further showed that F. pseudograminearum soil populations were lower under deep plowing than under rotary tillage or deep loosening, but similar across sampled soil depths. This was associated with alterations in both fungal and bacterial soil microbiota. Interestingly, a greater diversity in soil microbiota was associated with higher levels of the pathogen.

What the Findings Suggest

In short, burying inoculum deeper reduced disease, at least in this system. I would speculate that could be broadly applied to many soilborne pathogens, including those affecting California strawberries (i.e., Macrophomina, Fusarium, Verticillium and Phytophthora).

Literature Cited

Zhou et al. 2025. Preceding crop straw return methods influence the disease severity of wheat crown rot. Phytopathology 115:783-793. https://doi.org/10.1094/PHYTO-12-24-0386-R