MPSG agronomists participated in the disease session of Crop Diagnostic School this year, highlighting two nefarious root rots: Phytophthora root and stem rot in soybeans and Aphanomyces root rot in peas.
‘Phytophthora’ is an unwieldy name to grasp. Its name is Greek, with ‘Phyto’ meaning ‘plant’ and ‘phthora’ meaning ‘destruction, decay, ruin or perish’. Put these together and we get the Plant Destroyer, Phytophthora root and stem rot. ‘Aphanomyces’ doesn’t have a similar fun break-down, but we can say we’re not A-fan-o’-mycetes. It’s cheesy, but memorable.
Both of these diseases have a few things in common, since they’re both oomycetes, or ‘water moulds’. Water being a key piece here, as both of these diseases require soil moisture for a portion of their life cycle so they can swim to infect plant roots. Since we’ve had drier years, they’ve been less common to observe in the field, but with a return of more moisture this season, we anticipate these being a larger concern. Both of these diseases are also long-lived in the soil as resting oospores, surviving 5 to 10 or more years.
These two root diseases are not alone in our soil, and will typically co-infect with Fusarium root rots. In annual disease surveys, we typically find some level of Fusarium root rot in every single soybean and pea field we survey. Keep those Fusarium root rots in mind as you consider root rot management of Phytophthora and Aphanomyces.
For Crop Diagnostic School, we put together a handy take-home covering the important points of Phytophthora and Aphanomyces root rots. You can check them out here for the full story:
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