Occurrence Patterns and Control Methods of Viral Diseases in Solanaceous Crops

In the southern Guangxi region, the winter climate is warm with no obvious frost, making it a great place for growing winter vegetables to be shipped from the south to the north. Therefore, after harvesting the late rice, farmers grow winter vegetables to supply the market after the Spring Festival, achieving relatively high economic returns and writing a new chapter of "the plan for the year lies in autumn and winter." This has become another way for local farmers to get rich and move toward a moderately prosperous life. Among the many vegetable varieties grown, solanaceous vegetables (tomato, pepper, eggplant) are favored by local farmers for their unique planting advantages. According to statistics, the perennial planting area is around 80,000 mu, and the planting area is predicted to keep rising year by year. However, during many years of cultivation in Hepu County, the damage from viral diseases, long known as "plant cancer," has caused "three-drop disease" (leaf drop, flower drop, fruit drop), bringing huge economic losses to vegetable growers. In mild cases, growth is stunted with fewer flowers and fruits; in severe cases, all leaves on the entire plant drop off and the plant dies. This has therefore drawn great attention from the vast number of vegetable growers and relevant departments. Based on several years of experience in plant protection work, the author now shares some views on the occurrence and control of the virus for the reference of vegetable growers.

1. Disease Symptom Identification

The symptoms mainly fall into two types: mosaic necrosis type and leaf deformity with clustering type.

(1) Mosaic necrosis type

Diseased leaves show obvious mosaic symptoms of alternating pale green and light green, and some develop brown necrotic spots. Necrotic streaks appear along the main vein of the leaf and along the stem. Leaves drop, flowers drop, and fruits drop, eventually leading to the death of the whole plant.

(2) Deformity with clustering

In the early stage, leaf veins lose their green color and mottled mosaic appears. Leaves thicken, narrow, and become linear. Stem internodes shorten and become deformed, and branches cluster. In the later stage, the plant becomes dwarfed. Fruits show mottling of dark green and light green, and diseased fruits are deformed and fall off easily.

2. Occurrence Patterns

The transmission routes of the viral disease vary with the type of virus source, but they are mainly divided into two major categories: insect transmission and contact transmission.

(1) Mosaic necrosis type

This disease is caused by Tobacco mosaic virus (TMV) and is transmitted mainly through sap contact, invading through tiny wounds on the plant. Its occurrence conditions include high temperature and drought, years of continuous cropping, tender plants, poor soil, and extensive management, all of which worsen the disease.

(2) Deformity with clustering

This disease is caused by infection spread by piercing-sucking insects such as aphids and thrips carrying Cucumber mosaic virus (CMV). It is severe under high temperature and drought and when aphids and thrips occur in large numbers.

3. Control Measures

At present, there is no specific pesticide to control this disease. It can only be prevented or effectively reduced through cultivation and technical management, early control of aphids and thrips, and other concentrated control measures, so as to achieve the goal of high yield.

(1) Select disease-resistant varieties

Tomato varieties include: Zhongza No. 7, Shuangkang No. 5, Zhongza No. 9, etc.;

Pepper varieties include: Jinjiao No. 3, Tianza No. 1, Tianza No. 2, Big Persimmon Pepper, etc.;

Eggplant varieties include: Qingxuan No. 4, Fengyan No. 1, Liaojie No. 3, etc.

(2) Carry out crop rotation to reduce disease damage

Solanaceous plants should not be continuously cropped with one another. They can be intercropped with tall crops such as sorghum and corn. The best approach is paddy-upland rotation with rice and other crops, which gives good disease control results. At the same time, cultivation should aim to grow strong seedlings, select disease-free seedlings for transplanting, combine with formula fertilization technology, apply sufficient base fertilizer, and water frequently. This allows the plants to grow vigorously and enhances disease resistance.

(3) Pesticide control

Aphids and thrips are the vectors that spread viruses in solanaceous plants, so aphids and thrips must be controlled early to reduce disease damage and achieve the effect of "controlling both insects and disease." The following options can be used: 20% Kangfuduo emulsifiable concentrate at 4000 times dilution + 20% Virus A wettable powder at 500 times dilution + amino acid foliar fertilizer mixed solution, or 10% imidacloprid wettable powder at 2500 times dilution + 2% ningnanmycin aqueous solution at 300 times dilution, or 1.5% Zhibingling II at 800 times dilution mixed with foliar fertilizer Lufenwei at 1000 times dilution. Spray the whole plant at the early stage of disease onset, applying continuously 3 to 4 times, with each interval of 7 to 10 days.