Rhizoctonia
Class: Fungi
Common Name
Root rot
Scientific name
Rhizoctonia spp
Potential Hosts
Eggplant, strawberry, pepper, tomato, basil, tarragon, mint, cabbage, cauliflower, pea, beans, soy, lettuce, cucumber, squash, melon, pumpkin, zucchini, watermelon, potato, carrot, beet, rice, sage, cucumber, radish, cotton, canola, wheat, barley, peanuts, corn, strawberry, turf grass, and tobacco
Who am I?
Rhizoctonia is a common seed-and soil-borne fungus with significant saprophytic characteristics (feeds on dead organic matter). Rhizoctonia causes “damping-off” in cultivated fields, ornamental plants, and turf grass. The pathogen overwinters on plant residue and soil.
Several types of rhizoctonia attack plants and are known by their non-host specialization; in other words, they can affect many types of plants. One such specie is rhizoctonia solani, which is the causal agent of black scurf of potatoes, violet root rot in carrots, bare patch of cereals, root rot of sugar beet, belly rot of cucumber, and sheath blight of rice.
Rhizoctonia favors high humidity conditions and can develop in a broad-spectrum of temperatures: 10-32c. Rhizoctonia tends to occur within the short time frame adjacent to planting; the fungi attacks plants at the soil line. Easy to spot symptoms of Rhizoctonia are "damping off" and reduced seed germination. Infected seedlings exhibit red to brown lesions primarily at the stem base. Red-brown to black lesions will form on roots. With time, infected seedlings will wilt, while older, more mature plants will exhibit an increased tolerance to the disease.
Control measures
Cultural
Monitoring: It’s easier and more cost effective to overcome infestations by controlling rhizoctonia in its initial stage. Make it a routine to monitor the field regularly and search plants for the presence of rhizoctonia on a weekly basis.
As with any moisture-favoring disease, various techniques can taken during crop growth to reduce the chances of an infection and spread:
Maintain adequate space: Avoid overdensity planting in order to allow light to penetrate and promote the quick drying of leaves and fruits on humid days.
Recurrence: Experiencing year-after-year outbreaks in the same field probably means soil is heavily contaminated. This justifies crop rotations and preventive measures such as soil disinfection. Solar disinfection of the soil (solarization or pasteurization) can be implemented in sunny areas; this involves covering prepared and moistened soil with a polyethylene film 35–50 μm thick and keeping it in place for at least one month during a sunny period of the year. Solar disinfection of the soil eradicates the presence of white mold on the top layers of soil. It is common for solar disinfection to be accompanied by fumigants such as metam-sodium.
Sanitation: Plant debris must be removed during cultivation and at the end of cultivation to diminish the presence of rhizoctonia within the soil.
Proper soil drainage: Standing water promotes the development of rhizoctonia.
*Drip irrigation is preferable to other methods of irrigation.
*Other moisture reduction techniques (during growth) include covering the ground with polyethylene sheets to reduce evaporation from the soil and help isolate vegetation in the soil.
Conventional (Chemical)
The following are fungicides used in one or more parts of the world: carbendazim, propiconazole, pencycuron, iprodione, and fludioxonil.
Biological
Trichoderma harzianum is a fungus being used as a fungicide and is known to help prevent rhizoctonia.
Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.