What's wrong with yellow tomatoes? how to prevent

The yellowing of tomato top leaves belongs to tomato yellow leaf disease, which requires timely pastoral cleaning, crop rotation, irrigation for more than 15 days, and appropriate postponement of sowing date. Seedling stage: the heart leaf is shrunk, the leaf color is slightly yellow, and the plant is short. Flowering stage: the plant was dwarfed obviously and grew slowly. Fruit stage: the disease is aggravated, the edge of the leaf is rolled up seriously, the quality of the leaf becomes hard and the edge is small, and the commerciality of the fruit is poor. In the later stage of growth, the leaves were yellow and wrinkled, but the yield was not affected.

Symptoms of yellowing of the top leaves of tomatoes

1. Seedling stage

The main results are as follows: (1) the yellowing of the top leaves of tomatoes can show slight susceptible symptoms 25-30 days after sowing, such as shrinking heart leaves, slightly yellow leaves, and plants will be shorter than normal seedlings.

(2) the seedling symptoms are relatively easy to identify in the high temperature season, and slightly alleviated in the low temperature season.

2. Flowering period

The main results are as follows: (1) the obvious symptoms begin to appear 40-50 days after tomato planting, and the flowering period is usually the peak period of yellowing of tomato leaves at the top.

(2) the main manifestations were obvious dwarfing, slow growth, yellowing, wrinkling and shrinking of the new leaves at the top, and thickening of the veins on the back of the leaves.

(3) the edge of the leaf is curled up, and some of the leaves become thicker, but the leaves remain green. If the plant is seriously infected, it will be seriously dwarfed and unable to set fruit normally.

3. Result period

The main results are as follows: (1) the general symptoms of the plants with yellowing leaves at the top of the tomato will be aggravated after entering the fruiting stage, especially in the yellowing leaves.

(2) some leaves remain green without yellowing, the edge of the leaf curls seriously, the leaf thickens obviously, the quality of the leaf becomes hard and smaller, and the vein on the back of the leaf gradually turns purple.

(3) some leaves will become narrower and narrower, and the distance between stem nodes will be significantly shorter and dwarf.

(4) compared with normal plants, diseased plants are obviously shorter, usually at 50cm~80cm height, and some plants can grow to a certain height, but the number of fruit set is less and the fruit is smaller.

(5) during the ripening period, the coloring of the fruit is uneven, the fruit is stiff, there are yellow and blue blocks between them, and the commerciality is poor.

4. Late growth stage

The main results are as follows: (1) the tomato plants infected with the virus are short in the later growth stage, the fruit quality is poor, and there is no commodity.

(2) the tomato infected by virus showed curling, yellowing and wrinkling leaves in the later growth stage, but had little effect on the yield.

How to prevent the top leaves of tomatoes from yellowing

1. Do a good job of rural cleaning in time

After harvesting the crops before planting tomatoes, it is necessary to thoroughly remove residual branches, fallen leaves and field weeds to reduce the number of Bemisia Tabaci pests.

2. Crop rotation and crop change

When growing tomatoes, we should promote flood-drought rotation and rice-vegetable rotation. We can also plant vegetables that Bemisia Tabaci do not like to eat, such as celery, lettuce, leeks, onions and garlic.

3. Irrigating the shed

The high temperature season in July and August is the season of high incidence of diseases and insect pests. During this period, the greenhouse land should be leveled in time, the soil ridges should be put on all sides, covered with old film, and the whole shed should be filled with water for more than 15 days, so as to eliminate Bemisia Tabaci and reduce the occurrence of soil-borne diseases.

4. Appropriate postponement of sowing date

If Bemisia Tabaci is difficult to control, sowing can be postponed to the middle and late September, which can reduce the occurrence of tomato yellow leaf curl virus disease.