Dr. Khin Hnin Yu - Purple Yellow Leaf Curl Virus Disease

Tomato yellow leaf curl virus disease

Introduction

This disease has been occurring in tomato fields in various parts of Myanmar for the past 3 years. It is getting worse every year. It is caused by a virus (8) like influenza, hepatitis, and other diseases in humans and avian influenza in animals. The name of the disease is “Tomato Yellow Leaf Curl Virus”. The virus that causes the disease is called Tomato Yellow Leaf Curl Virus in English and its abbreviation is TYLCV. Fortunately, the same diseases that affect humans and animals do not affect plants, and the same viruses that affect plants do not affect humans and animals.

Currently, this disease has been reported in almost every tomato-growing country in the world, including the United States, Mediterranean and Middle Eastern countries, African countries, Asian countries such as Japan, China, Nepal, India, Taiwan, and Thailand, as reported in foreign research journals and websites. It is also considered an important disease due to its economic losses. This disease was first detected in Sudan in 1965, in Israel in 1966, in Cyprus (S) in 1974, in Tanzania in 1990, and in Bangladesh (S) in 1991.

In Myanmar, tomato farmers say that this disease has been noticeable for about 3 years. There is no specific record of the year it first appeared.

In terms of disease severity, a 2004 paper by the Asian Vegetable Research and Development Institute in Taiwan reported that the disease incidence in some fields quickly reached 100%. This means that 100 out of 100 plants were infected. A 2001 paper reported that the disease was highest in the western mountains of Nepal during the rainy season, and that the yield of the infected field before flowering was 95%. A 2004 report from Bangladesh (Shah) stated that this disease was the most destructive of all tomato diseases. Although the number of African countries has decreased in the past decade, there is no evidence of fruit deformation or browning. Tomato is also susceptible to other viral diseases, and if the disease is caused by a fungal disease, the fruit is deformed and has dark brown spots on the inside.

If only one (or more) of the symptoms are seen, it is not certain that this disease is the cause. This is because other viruses (e.g., potato leaf curl virus, potato leaf curl virus, potato smut virus, and potato leaf spot virus) can also infect tomato plants, and some of the symptoms are similar, so they can be mistakenly identified. However, if at least 34 of the above symptoms are present at the same time, it is certain that this disease is the cause. This disease not only causes the symptoms mentioned above, but also reduces the quality of the fruit, such as softness, thickness, and soluble nutrients.

Ways of spreading infection

The virus that causes this disease is mainly transmitted by a very small (2-mm long) insect called the whitefly. Its scientific name is Bermicka tahari. This whitefly is also called the silverleaf whitefly because of the silvery color on its wings. (Figure 5) Up to 100% of all infections are transmitted by vectors.

Whiteflies prefer hot, dry weather and are active during this season. Heavy rains can reduce the number of whiteflies. Under normal conditions, whiteflies rest on plants during the day and feed, and are carried by the wind. At night, they gather on the underside of leaves and begin to lay eggs (Figure 6).

When a whitefly feeds on the leaves of an infected tomato plant, the virus particles are carried from the leaves and the stem (pat ap) into the whitefly's body. The feeding time required for the virus to reach the whitefly's body is 15 to 30 minutes, and most females are more aggressive than males.

It spreads more. After the latent period of 10 hours, when the infected whitefly feeds on a healthy leaf, the virus enters the leaf through the mouthparts of the whitefly and infects the plant. This type of transmission is called the persistent mode of transmission. The virus multiplies in the body of the host and remains there for a long time. If the virus is attached to the mouthparts of the host and feeds on a healthy leaf, the host immediately enters the leaf and infects the plant, this mode of transmission is called the non-persistent mode. There are 8 different types of viruses. The virus that causes this disease is transmitted by the persistent mode.

The time required for a whitefly carrying the virus to feed on a plant to infect the plant is 10 to 30 minutes. A foreign research paper reported that 12 hours after feeding on an infected plant, about 6 million viruses have already developed in the body of the whitefly. The virus is transmitted from one whitefly to another through mating between male and female whiteflies. Therefore, the virus-infected whiteflies spread in the whitefly colony, so that there are whiteflies with the virus even in places where there are no infected plants. The virus can survive in the body of the whitefly for up to 12 days, but some reports say that it is not transmitted through eggs, while another report says that it can be transmitted through eggs to two generations. The virus is not transmitted from infected plants to plants through sap or seeds. It is reported that it can be transmitted through grafting.

Prevention and suppression methods

Here are the methods proposed by various countries to prevent and control this disease. If we try to do everything possible depending on the situation, we will be able to effectively prevent and control it. (1) Although it is a viral disease, we do not need to spray antiviral drugs. There is no cure.

The only thing that needs to be controlled is the whitefly, the insect vector that transmits the disease. If a large population of whiteflies is expected, resistant tomatoes should be planted.

(2) Grow tomatoes in a place away from tomato fields and other cultivated areas.

Or, you can plant the seedlings in a filter chamber that is impervious to whiteflies. Whiteflies are 1 to 2 mm long, so use a filter with a size 50 mesh (50 holes per mesh) or smaller. This will prevent the disease from entering the seedlings early. If you don't have a filter with such small holes, the whiteflies can enter.

If you use a filter, spray the filter with insecticide. (3) Carefully inspect the seedlings and remove any plants that show signs of disease.

They should be uprooted and destroyed immediately. (4) Whiteflies prefer young plants, so do not harvest seedlings older than 30 days.

You should transplant only virus-free seedlings.

(5) Avoid planting when the whitefly population is high.

This disease can be prevented. (6) If grown in a greenhouse, cover windows and doors with insect-proof screens.

(7) Whiteflies can attack plants of many plant species.

There are many host plants. Therefore, it is necessary to remove host plants near the plantation that can harbor whiteflies (e.g., pea plants, eggplant, yams, cotton plants, yams, peanuts, beans, yams, okra, spinach, yams, daisies, potatoes, and black locust trees).

If you want to plant these plants, you should plant them separately at different times and places. (8) Take care to keep the field clean so that there are no weeds. (9) Do not plant tomatoes once and then harvest them before they are ready. This is because the whiteflies, the vectors, can continuously attack them. If you plant old plants (old fields) and new plants (old fields) close together, both the whiteflies and the virus will continuously attack them. Remove (burn or destroy) old plants as soon as possible when the fruit is ready. (10) If you see any signs of disease, cover the plants with plastic wrap.

Cover the plant with a clear (or black) plastic bag, tie the bag tightly around the base of the plant, and cut the plant from the bottom of the plastic bag. Leave the bag and plant on the ground in the field for 1 to 2 days. This is to trap the whiteflies, and do not cut the plant with a knife or put it on the compost pile. Remove it from the planting hole and

It must be burned.

If you see symptoms but no whiteflies, cut the plant from the base and add it to the compost pile.

(11) The base of the plant is covered with straw, yellow plastic (or ultraviolet)

Cover with a light reflector. This will reduce the incidence of whiteflies. (12) Adding fertilizers containing silicon and calcium to the soil will thicken the cell walls on the surface of the leaves and make the plants more resistant to whiteflies.

The damage may be reduced as the pest becomes resistant. (13) Whitefly infestation should be monitored twice a week.

If you see whiteflies, spray with insecticide, insecticide oil, insecticide soap solution. Spray 2 types of insecticides alternately at a time. This is to prevent drug resistance. The amount of pesticide to be used, the number of times to spray, the interval. The points to be observed must be followed. Be careful to keep the lower surface of the leaves wet when spraying. Dilute 40 to 60 cc of insecticide in 1-gallon of water (or) dilute 1 to 20 cc of abomettin insecticide in 1-gallon of water and apply every 5 days.

You can spray it. (14) If the disease is severe, dilute 1 bag of Dimethoate (Ibikethale) with water.

11 to 20 cc per gallon, Deltamethrin (Deltamethrin) 15 to 25 cc per gallon of water, Imidacloprid (Imidacloprid) 2 to 3 grams per gallon of water

You can spray at a rate of . Note: Alcohol (1) Prevention and control methods from numbers (1) to (12) are methods that do not use pesticides.

When a disease occurs in a field, you should not hesitate to spray pesticides immediately. Using pesticides is also expensive and if the system is not followed, the sprayers may be poisoned and the pest control may not be effective. In Inle Lake, fish, shrimp and small aquatic animals in the water are also poisoned and die. It will also cause environmental pollution. Therefore, safe and cost-effective pesticide-free agriculture is needed.

Practices should be prioritized. (2) Number (7) includes clearing other host plants of white flies. These plants should be

If you cut/clean the plants only after they have been heavily infested with whiteflies, the whiteflies on those plants will migrate to the tomato plants.

It comes. So if you clear other receivers, you will get the number.

You should do as mentioned in (9). (3) The new plantation mentioned in number (9) should be close to the old plantation.

It is most commonly found in farms around Inle Lake.

Early planting, late planting, and replanting after each harvest result in a new crop being overcrowded with old crops, and pests and diseases from the old crop are spreading to the new crop. Whether it is in a single-owner farm or in farms owned by several people, care should be taken to prevent this situation. Removing the rows and poles of the unfruitful crop and burning the old plants as soon as possible is a very effective way to prevent and control pests. ) Although the use of pesticides is mentioned in numbers (13) and (14), if the same type is used repeatedly, it will lead to drug resistance and the pests will not be killed. It should be noted that whiteflies quickly become resistant to pesticides. Use 2 *

Do not spray more than once and spray alternately. If I had to share what the agricultural experts from India said in Inle.. I sprayed Imidacloprid on this plant to control the whitefly, but later it could not be controlled, so I changed to Acetyl Meprix. That can be effective in the early stages, but it will not be effective later. So I sprayed Dinotifuram and it will not be effective later. So when I finally added silicon fertilizer to the soil, the whitefly attack on the plants decreased and the disease also decreased. Because of the silicon, the cell walls of the leaves of the cotton plant became thicker/harder and more resistant to the whitefly.

Therefore, it is clear that if plants are affected by diseases or pests, we should not rely on pesticides. It is also important to consider that the immune system of plants can respond to diseases and pests / increase resistance. Like silicon, calcium, copper, sulfur, potassium also have the properties to increase plant resistance.