Stem rot is a category of plant diseases in which a pathogen, usually a fungus or oomycete, infects and decays the stem of a crop plant, often resulting in lodging, reduced yield or plant death.[1][2] The term is applied to diseases of many different crop species and is caused by a heterogeneous group of soil-borne and seed-borne pathogens; the most economically important include several species of Sclerotinia, Phytophthora, Fusarium, Pythium and Rhizoctonia on broadacre crops and Sclerotium oryzae on rice.[1][3][2]
Symptoms
editSymptoms of stem rot vary with the causal pathogen but commonly include water-soaked or discoloured lesions on the lower stem, wilting, yellowing of foliage, lodging, and partial or complete plant death.[4][5] The fungus or oomycete impedes vascular transport of water and nutrients through the stem, and water may leak from lesions in stem tissue.[1] Some pathogens produce visible signs in addition to symptoms, such as the cottony white mycelium and small black resting structures known as sclerotia characteristic of Sclerotinia sclerotiorum infection, or the dark chocolate-brown lesions that extend from below the soil line up one side of the stem in Phytophthora infections.[1][6][5]
Pathogens
editSclerotinia stem rot
editSclerotinia stem rot, also known as white mold, is caused by Sclerotinia sclerotiorum, a hemibiotrophic fungus with an unusually wide host range of more than 400 plant species.[7][8]
The pathogen survives in soil as melanised sclerotia for up to five to eight years.[8][7] Under cool, moist conditions during the host's flowering period, sclerotia in the upper soil profile germinate carpogenically to produce small, cup-shaped apothecia that release millions of airborne ascospores.[1][7] Ascospores cannot infect healthy living tissue directly; they first colonise senescing flowers or other dead plant tissue, from which the fungus then advances into the living stem at the nodes.[8][6]
Phytophthora root and stem rot
editPhytophthora root and stem rot of soybean is caused by the oomycete Phytophthora sojae, and is one of the most damaging soybean diseases in the northern United States.[4][5][9] The pathogen survives in soil as long-lived oospores, which germinate in saturated soil to release motile zoospores that swim through soil water to infect soybean roots.[5][9] Infection progresses up the stem, producing a characteristic dark brown lesion extending from the soil line.[5][10] Disease development is favoured by heavy, poorly drained soils and warm temperatures above 60 °F (16 °C).[4][5] Phytophthora sojae is genetically diverse, with over 200 pathotypes detected in some regions, complicating management based on race-specific resistance.[4]
Other causal agents
editA number of additional soil-borne fungi cause stem and stalk rots on cereals, legumes and vegetables. Fusarium species, including Fusarium culmorum, cause stem and root rots on wheat and barley.[1] Pythium species are common cause of damping off and root rot in seedlings, particularly under cool, wet conditions.[4] Rhizoctonia solani causes stem and crown rots in a wide range of hosts including soybean and many vegetable crops.[1] Sclerotium oryzae (sexual stage Magnaporthe salvinii) causes the principal stem rot of rice, which can cause yield losses of 30–70 per cent in heavily infected fields.[2][11]
Disease cycle
editMost stem rot pathogens are persistent in soil through specialised resting structures, including sclerotia (Sclerotinia and Sclerotium), oospores (Phytophthora and Pythium), and chlamydospores (Fusarium), which can remain viable for several years between susceptible host crops.[1][9][11] Spores or mycelium from these resting structures infect plants when environmental conditions are favourable, with most stem rot pathogens requiring high soil moisture for either germination or dispersal of infective propagules.[5][2] Once the host is infected, the fungus or oomycete colonises stem tissue, and new resting structures form within or on the diseased tissue and return to the soil at the end of the growing season, completing the cycle.[1][8]
Management
editBecause the resting structures of stem rot pathogens are long-lived in soil, no single management tactic provides reliable control, and most extension programs recommend an integrated pest management (IPM) approach combining cultural, genetic, biological and chemical methods.[8][9]
Cultural practices include crop rotation with non-host crops to reduce inoculum, adjusted row spacing and seeding rates to modify canopy microclimate, improved drainage on heavy soils, and the use of clean planting material and sterile equipment to limit pathogen spread.[8][7][4] Crop residue from infected fields is a primary source of subsequent-season inoculum and is often managed by tillage, burning, or extended rotation.[2][11]
Resistant cultivars are the most effective management tactic for Phytophthora root and stem rot, with race-specific resistance conferred by single dominant Rps genes and supplemented by quantitative (partial) resistance.[4][10][9] Resistance to Sclerotinia sclerotiorum has remained partial across cultivars and is inconsistent under field conditions.[8][7]
Fungicides are used for Sclerotinia stem rot during the host's flowering period, timed to coincide with apothecial development and ascospore release.[7][6] Forecasting models, including the smartphone-based Sporecaster tool developed by the University of Wisconsin–Madison and validated in Wisconsin, Iowa, Michigan and Nebraska, are used to time fungicide applications based on apothecial development risk.[8] Biological control with antagonistic fungi such as Coniothyrium minitans, which parasitises sclerotia, is also used in some systems.[8]
Economic impact
editStem rot diseases collectively cause substantial annual yield losses in major broadacre crops. Sclerotinia stem rot in soybean produces yield reductions of roughly 5 to 10 bushels per acre at 10 per cent disease incidence, and in epidemic years can cause losses on the order of one million metric tons across the United States.[6][1] Stem rot of rice has been recorded as one of the major constraints on rice production in parts of South and Southeast Asia, with reported losses of up to 60–70 per cent in heavily infected fields.[11] Phytophthora root and stem rot is a leading cause of stand establishment failure in the northern United States soybean production region.[4][9]
Causal species and hosts
editThe following table lists species reported to cause stem or stalk rot, with their principal hosts:
| Species | Hosts |
|---|---|
| Cladosporium ear rot | maize/corn |
| Fusarium culmorum | wheat, barley |
| Glomerella graminicola | maize, sorghum, ryegrass, bluegrass, barley, wheat |
| Gibberella zeae | maize |
| Phialophora gregata, Cadophora gregata, Brown stem rot (BSR) | soybeans |
| Phyllachora maydis | maize |
| Phytophthora capsici | cucumbers |
| Phytophthora sojae[12] | soybean |
| Phytophthora tentaculata | Chrysanthemum, Verbena, Delphinium ajacis |
| Pythium graminicola | bent grass, turmeric, cotton, barley, wheat, rice, beans, peas, sugarcane |
| Rhizoctonia | |
| Sclerotium oryzae[13] | rice |
| Sclerotinia sclerotiorum (White mold) | beans, can befall more than 350 species |
| Stenocarpella maydis | corn, canes |
| Waitea circinata | maize |
Causative chemical agents produced by these fungal species may include mycotoxins: Trichothecene. Nematodes may cause symptoms similar to stem or stalk rots.
See also
editReferences
edit- 1 2 3 4 5 6 7 8 9 10 Peltier, Angelique J.; Bradley, Carl A.; Chilvers, Martin I.; Malvick, Dean K.; Mueller, Daren S.; Wise, Kiersten A.; Esker, Paul D. (2012). "Biology, Yield Loss and Control of Sclerotinia Stem Rot of Soybean". Journal of Integrated Pest Management. 3 (2): B1–B7. doi:10.1603/IPM11033.
- 1 2 3 4 5 "Stem Rot of Rice". UC IPM Pest Management Guidelines: Rice. University of California Agriculture and Natural Resources. Retrieved 25 May 2026.
- ↑ Giesler, Loren J. "Soybean Disease: Sclerotinia Stem Rot". University of Nebraska-Lincoln. Retrieved 25 May 2026.
- 1 2 3 4 5 6 7 8 "Plant Disease: Phytophthora Root and Stem Rot". University of Nebraska-Lincoln Institute of Agriculture and Natural Resources. 2021. Retrieved 25 May 2026.
- 1 2 3 4 5 6 7 "Phytophthora root and stem rot on soybean". University of Minnesota Extension. Retrieved 25 May 2026.
- 1 2 3 4 Chilvers, Martin. "Sclerotinia stem rot of soybean: identification, factors and management". Michigan State University Extension. Retrieved 25 May 2026.
- 1 2 3 4 5 6 Dorrance, Anne; Mills, Dennis. "Sclerotinia Stem Rot (White Mold) of Soybean". Ohioline. Ohio State University Extension. Retrieved 25 May 2026.
- 1 2 3 4 5 6 7 8 9 Khambhati, Vivek Hemant; Chen, Zhi-Yuan (21 November 2025). "Integrated Pest Management of Sclerotinia Stem Rot in Soybean: Current Strategies and Future Prospects". Journal of Fungi. 11 (12) 823. doi:10.3390/jof11120823. PMC 12734104.
- 1 2 3 4 5 6 Mueller, Daren; Sisson, Adam (2024). "An Overview of Phytophthora Root and Stem Rot". Crop Protection Network. Retrieved 25 May 2026.
- 1 2 "Phytophthora Root and Stem Rot of Soybean". North Dakota State University Agriculture. 2025. Retrieved 25 May 2026.
- 1 2 3 4 Singh, Vipin Kumar; Pandey, Ajay Kumar (2024). "Stem rot: a recent threat to rice cultivation". Indian Phytopathology. 77 (3): 549–562. doi:10.1007/s42360-024-00757-7.
- ↑ Plant Disease: Phytophthora Root and Stem Rot, University of Nebraska–Lincoln, Institute of Agriculture and Natural Resources, accessed 2021
- ↑ Stem Rot of Rice, University of California AGRICULTURE AND NATURAL RESOURCES Integrated Pest Management Program, 2004