Latest Causes and Control Measures of Wheat Root Rot

It occurs in all wheat-growing countries; in China it mainly occurs in Northeast China, Northwest China, North China, Inner Mongolia and other regions, and in recent years it has continued to expand, with cases also found in the wheat-growing areas of Guangdong and Fujian. The symptoms are similar to those of root drowning disease. After the underground roots are infected by the pathogen, it first spreads gradually from the fibrous roots to the branch roots and then to the main root, and the color gradually turns dark brown. After the disease develops, the underground roots slowly rot; in the early stage there are no obvious symptoms on the aboveground stem, but over time, without the roots supplying fertilizer and water, the stem will wither, the branches and leaves will turn yellow, and eventually the plant will die. Wheat, strawberry, Scutellaria baicalensis, Salvia miltiorrhiza, Isatis indigotica, Astragalus membranaceus, Pseudostellaria heterophylla, peony and Codonopsis pilosula are susceptible to this disease.

Main causes of wheat root rot

Wheat is continuously cropped for many years, soil organic matter is relatively low, and unfavorable weather adds to the impact; or because the soil is hilled too high where the crop is planted, or fertilizer is applied in furrows on both sides or weeds are removed, causing damage to the root system; or because during rain or irrigation the water volume is too large and drainage is not timely; or because of insufficient light, low temperature and high humidity, excessive soil stickiness, soil clodding, and poor ventilation; and also when the root system is damaged and broken, it is most susceptible to pathogen invasion. Root rot occurs frequently in the rainy season.

Characteristics of wheat root rot

Wheat root rot is caused by the fungus Fusarium solani (Mart.) App. et Wollenw., a deuteromycete of the subdivision Deuteromycotina, which is the chief culprit causing root rot. Insufficient light, high soil stickiness/large water volume, poor ventilation, and root damage are all main causes of pathogen invasion. The pathogen infects the roots, first forming brown to black lesions on the coleoptile, young leaves, root crown, root neck and underground stem, which gradually expand and cause them to rot, thereby causing dead seedlings or dead plants. After the disease develops, the roots gradually change from light brown to dark brown. The pathogen remains in the soil to overwinter, enters the crop the following year through the above causes, and spreads through irrigation or rain.

Effective measures to control wheat root rot

Controlling wheat root rot combines agriculture and pesticides.

1. Agricultural control methods

① Because large accumulations of water and untimely drainage can trigger this disease, choosing relatively flat soil for planting is also very necessary.

② If the soil in the planting area is not level, that is all right, but drainage work must be done well to discharge accumulated water, especially in the rainy season.

③ Excessive soil viscosity easily causes soil clodding and tends to cause poor root development. This is similar to the principle that wearing clothes that are too tight makes the body uncomfortable.

④ Everyone knows that using any fertilizer that has not been fully decomposed easily increases the incidence of disease; the damping-off disease introduced earlier also has this cause. Apply decomposed organic fertilizer, potassium fertilizer and phosphorus fertilizer to make the plants “strong” so as to enhance disease resistance.

⑤ For seedbed selection, the seedbed for crops to be raised should preferably be one used for a different crop last year, that is, crop rotation should be practiced.

⑥ Choosing high-quality seeds is also a good option. High-quality seeds can also resist the occurrence of disease to a large extent.

2. Pesticide control is closely related to hymexazol and metalaxyl-hymexazol

As with other diseases, pesticide control of root rot first involves seed disinfection, then soil disinfection, and finally the choice of root-drenching medication for crops after the disease develops.

① Seed disinfection before planting. This is also the most common first step to reduce disease. Dosage for seed disinfection: because the area of seeds is smaller than that of soil treatment, seed dressing can use a relatively lower dilution of the drug. 600-800 times dilution of hymexazol or 800-1000 times dilution of metalaxyl-hymexazol.

② Soil disinfection before planting. The second step to reduce disease. Soil disinfection uses a relatively higher dilution of the drug than seed disinfection. 1200-1500 times dilution of hymexazol or 1500-2000 times dilution of metalaxyl-hymexazol.

③ Root drenching after the disease develops. The third step to reduce disease. Root drenching is similar to soil disinfection, and the application area is relatively large, so the dosage is the same. 1200-1500 times dilution of hymexazol or 1500-2000 times dilution of metalaxyl-hymexazol.