Main Pests and Diseases in Sorghum Cultivation and Their Control Methods
Which pests and diseases should be mainly controlled when growing sorghum? Please provide guidance. The following pests and diseases should be controlled when growing sorghum: 1. Sorghum smut. Sorghum smut is a common disease on sorghum in Liaoning. It includes head smut, loose smut and covered smut. Symptom identification: head smut shows obvious symptoms after heading. Diseased plants are generally shorter. Before heading, the lower part of the diseased head swells, the husk leaves are tight, and there is a white club-shaped mass inside. After heading, a large amount of black powder is scattered.
Which pests and diseases should be mainly controlled when growing sorghum? Please provide guidance.
The following pests and diseases should be controlled when growing sorghum:
1. Sorghum smut
Sorghum smut is a common disease on sorghum in Liaoning. It includes head smut, loose smut and covered smut.
Symptom identification: head smut shows obvious symptoms after heading. Diseased plants are generally shorter. Before heading, the lower part of the diseased head swells, the husk leaves are tight, and there is a white club-shaped mass inside. After heading, a large amount of black powder is scattered.
In loose smut, generally the whole head is affected, but the head shape is normal. The grains, however, become oblong small gray galls, which rupture after maturity and release the black powder inside.
In covered smut, usually all grains in the head become egg-shaped gray galls. The outer membrane is hard and does not rupture, or only slightly splits at the tip, and the inside is filled with black powder.
Occurrence characteristics: sorghum head smut is transmitted through seeds and soil, mainly through soil. Chlamydospores survive in the soil for about 3 years. When sorghum seeds have just emerged from the white tip to a sprout length of 1-1.5 cm, they infect young sorghum sprouts. The pathogens of sorghum loose smut and covered smut mainly attach to the seed surface as chlamydospores. After diseased seeds are sown, the pathogens germinate at the same time as the seeds and invade host tissues. After the pathogen invades, the hyphae spread to the seedling growing point, and then elongate upward as the plant growing point grows, finally forming teliospores in the head.
Control methods:
(1) Select disease-resistant improved varieties according to local conditions.
(2) Chemical seed treatment is the most important, simplest and most effective method for controlling sorghum smut. ① Treat seeds with 2% Raxil at 0.1-0.2% of seed weight (seed treatment with rice-water slurry) or with 50% hexaconazole at 0.5% of seed weight. ② Use 100 ml of 20% triadimefon EC, add a small amount of water, and treat 100 kg of seeds, striving to mix evenly and spread out to dry before sowing. ③ Use 0.5 kg of 20% carboxin EC (or wettable powder), add 3 kg of water, and treat 40 kg of seeds, cover the seeds for 4 hours, then dry and sow.
(3) Implement crop rotation of more than 3 years to reduce the amount of inoculum in the soil. This is an important measure for controlling smut.
(4) Advocate timely late sowing to strive for early emergence and full emergence. Cut down diseased plants in time. Before the gray galls rupture, cut down the diseased plants, pull them out of the field, and destroy them centrally.
2. Sorghum aphid
The aphids damaging sorghum are mainly the sorghum aphid, followed by the English grain aphid, the oat bird-cherry aphid, the corn leaf aphid, the rose-grass aphid and Tetraneura ulmi, collectively called sorghum aphids.
Damage characteristics: sorghum aphids parasitize on the underside of host crop leaves and suck nutrients. In the early stage, they mostly damage the lower leaves, then gradually spread to the upper leaves of the plant, and secrete large amounts of honeydew, which drips onto the lower leaf surface and stems, making them shiny and oily. This affects plant photosynthesis and normal growth, causing leaf color to turn red, "bald necks" and "blunt tips", small heads and few grains, and affecting sorghum yield and quality.
Occurrence characteristics: sorghum aphids have short generations and reproduce quickly. They overwinter as eggs on Miscanthus sacchariflorus. After sorghum emerges in June, they migrate into sorghum fields to reproduce and cause damage, appearing in spots and patches at the seedling stage. During this period, if the average temperature remains above 22°C for two consecutive ten-day periods and rainfall is below 25 mm (high temperature and high humidity), sorghum aphids may break out. Conversely, if rainfall is relatively high and temperature is relatively low during this period, it is not favorable for aphid occurrence.
Control methods:
(1) Eliminate central aphid-infested plants (that is, "nest honey") early. The method may be to lightly prune aphid-infested lower leaves and take them out of the field for destruction. For spot and patch application, use 0.5 dimethoate powder or 40% dimethoate EC at 1500 times dilution.
(2) Use 50 g of 40% dimethoate EC per mu, mix evenly with an equal amount of water into 10-13 kg of fine sandy soil to prepare dimethoate toxic soil, and broadcast it over sorghum plants before heading.
(3) Use 5% phorate granules for fumigation. Use 200 g of phorate per mu, mix with 5-10 kg of sandy soil, and spread into furrows, spreading 1 furrow every 12 furrows. It has a special effect.
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