Occurrence and Control Methods of Rust Disease in Small Spring Crops: Barley, Wheat, and Broad Bean

Rust disease is a type of plant disease caused by parasitic rust fungi. It is widely distributed and highly destructive, and is most commonly seen in cereal crops, leguminous plants, and pears. The rust diseases of many crops are worldwide in scope, and some have the characteristic of large-region epidemics, with yield losses often counted in tens of thousands of tons. So what are the occurrence and control methods for rust disease in small spring crops (barley, wheat, and broad bean)?

1. Broad bean rust mainly damages leaves and stems, and in severe cases also damages pods. In the early stage, pale white or light yellow small granular spots appear on both the front and back of the leaves, then turn rust-brown and bulge like small pustules. After the epidermis of the small pustules ruptures, rust-brown powder is released. Later, black oval swollen spots appear, and after rupturing, black powder is released. Damage to stems and pods is similar to that on leaves, and severely affected plants often die prematurely.

Control measures for broad bean rust among broad bean disease controls:

1. Select early-maturing, disease-resistant, high-yielding varieties, plant early and harvest early, and avoid the peak disease period.

2. Practice crop rotation, and rotate with crops other than peas.

3. Do a good job of ditching and drainage; in low-lying land, make high beds and deep ditches to lower the groundwater level and field humidity.

4. Remove diseased plant residues and carry out deep plowing.

5. During the flowering and pod-setting stage, if the year is rainy, spray 0.4-degree lime-sulfur mixture, or 120—150-fold potassium sulfide solution 3—4 times, which has a good control effect.

2. The control of wheat leaf rust is basically similar to that of stripe rust. When stripe rust and leaf rust occur together, general control of stripe rust also controls leaf rust at the same time. However, the following points should also be noted.

1. Strengthen breeding work for resistance to leaf rust. In production, slow-disease varieties can also be used to delay disease onset and reduce disease severity.

2. Eliminate volunteer wheat seedlings to reduce sources of inoculum. Because wheat leaf rust can oversummer on volunteer wheat seedlings, eradicating volunteer wheat seedlings in fields and at field edges can reduce the amount of inoculum and is conducive to controlling major outbreaks of leaf rust.

3. Chemical control is the same as for stripe rust, but the appropriate time for spraying at the adult plant stage is from wheat booting to heading, when the rate of diseased leaves reaches 5%.

3. The barley leaf rust pathogen oversummers in the form of urediniospores on volunteer barley seedlings. After sowing and emergence, it infects autumn seedlings and overwinters on wheat seedlings in the form of mycelium or uredinial pustules. In spring, as temperatures rise, it resumes development, reproduces, spreads, and causes damage.

1. Select disease-resistant varieties. Disease resistance differs among varieties, and each locality can choose according to local conditions.

2. Strengthen field management. Fertilize rationally, eradicate volunteer wheat seedlings, and reduce sources of inoculum.

3. Chemical control. Spraying agents include 20% triadimefon emulsifiable concentrate, 95% nabam original powder, and 65% zineb wettable powder. For details, see the chemical control section for wheat rust.

Appendix: Symptoms of rust disease

Many light yellow small spots appear on the back of the leaves, then gradually expand and become yellow-brown raised pustules. After the epidermis covering the pustules ruptures, reddish-brown powdery material disperses, and chlorotic spots form at the corresponding sites on the front of the leaves. These pustules are the uredinia of the pathogen, and reddish-brown oval urediniospores are produced inside the uredinia in powdery form. Uredinia sometimes also occur on the front of the leaves. On a single leaf, the number of uredinia can even exceed 2,000, and in severe cases the diseased leaves dry up and fall off. In the late growth stage, dark brown pustules, namely telia, grow on the diseased leaves, and after the epidermis ruptures, dark brown teliospores are released. In Yongping County, the rate of rust-diseased fields reached 30-85%, and the rate of diseased plants was as high as over 90%. Therefore, timely chemical control of pests and diseases should be carried out to control the spread, creeping expansion, and severity of damage of the disease in the middle and late stages. It is recommended to use 15% triadimefon, applying 80 grams (1 packet) per mu, diluted with water and sprayed evenly.