Fusarium species are the most predominant pathogens contributing to the root rot complex in pulse crops.
Fusarium root rot causes severe root damage, preventing water and nutrients from flowing to the aboveground plant material and leading to premature plant death.
The sheer number and broad host range of Fusarium species, combined with few control options, make Fusarium root rot a challenging disease to manage in pulse crops.
The seedling stage is most susceptible to infection.
Impact
Fusarium spp. infections can cause yield losses in pulses from 10–30%, and severe infections under ideal environment conditions can be as high as 60% in field peas. Survey results from 2015–2018 found that F. avenaceum and F. solani were present in over 99% of pea and lentil fields sampled across the Prairies.
Yield loss can be challenging to assess because of the numerous indirect effects on the crop and the timing of the initial infection. Infections during the early seedling stage are much more detrimental than later infections.
Causes
Fusarium root rot is caused by a complex of Fusarium species (80 species worldwide) that can differ in preference for host crops and vary in their level of aggressiveness. Commonly found species in Western Canada include F. avenaceum, solani, redolans, oxysporum, culmorum, and poae, among many others. Pulses are more susceptible to Fusarium species than cereals or oilseeds, making Fusarium root rot the most common root disease in pulse crops.
The most common species in Western Canada is F. avenaceum, which can infect up to 200 host plants, including wheat, barley, canola, flax, chickpeas, and alfalfa. F. avenaceum causes particularly aggressive infections in peas and lentils, resulting in significant crop damage.
The F. solani species complex is also very aggressive on pulses and is peas’ most virulent Fusarium species.
For additional information on other fusarium species, see the resource below.
Fusarium spp. can survive in both soil and previous crop residue. Fields with tighter host crop rotations will build the inoculum of Fusarium spp. and contribute to increased infection risk in future crops. Fusarium root rot can occur under various growing conditions, and the plant must first be stressed for a host crop, such as peas or lentils. Typical environmental stressors include extreme soil moisture (flooding, excessive rainfall, poor soil drainage, or drought), high soil temperature (22–30˚C, acidic soils (pH 5.1–6.2), and low fertility. Soil compaction, such as field entrances and heavy clay soils, can favour Fusarium root rot and increase incidence and severity. Warm and moist conditions can favour both Fusarium and Aphanomyces, increasing the severity of root rot, with the most severe infections occurring at 25–30°C in moderately moist soils. Fusarium root rot commonly occurs alongside Aphanomyces root rot and can mask Aphanomyces symptoms. Fields with a history of root rot will experience more disease due to the higher amount of inoculum present in the soil.
