What causes tomato stem rot fruit? Detailed explanation of symptoms and causes
Symptoms and causes of stem rot fruit in tomatoes
Symptom identification: Tomato stem rot fruit, commonly known as "black stem," has two distinct types: the browning type and the whitening type, with the browning type being the most common. Browning-type stem rot fruit: It begins during the young fruit stage and mostly occurs on the lower part of the plant. During the fruit enlargement stage, the fruit surface colors unevenly, and then local browning appears. When the fruit is cut open, the vascular bundles inside the peel can be seen to be dark brown or tea brown. In mildly affected fruit, some vascular bundles turn brown and necrotic, and the fruit's external appearance shows no change, but the browned vascular bundle areas do not turn red; in severely affected fruit, all the vascular bundles in the flesh are dark brown, and the fruit surface is uneven, making it unfit to eat. Whitening-type stem rot fruit: It occurs from the green-ripe to red-turning stage. The fruit colors poorly, and externally the red portion of the fruit is reduced, with a waxy luster on the diseased parts. When the fruit is cut open, the flesh can be seen to be "pithy," and white or brown fibrous strands appear in the peel and the middle rib portions of the locules. The diseased fruit's flesh hardens and its quality is poor. Stem rot disease generally occurs only on the fruit, and no obvious symptoms can be seen on the stems and leaves. In severe cases, the plant top and lower leaves may sometimes be seen to bend, with the midribs of the leaflets protruding. When the stem is cut open at 70 cm from the root, brown lesions can be seen in the stem's conductive tissue.
Cause: The causes of tomato stem rot fruit are very complex. Preliminary analysis suggests that insufficient carbohydrates in the tomato plant and a decline in the carbon-to-nitrogen ratio cause metabolic disorder, leading to lignification of the vascular bundles, which is the direct cause of the disease. Many adverse environmental conditions, such as insufficient light, low temperature and high humidity, poor air circulation, insufficient carbon dioxide, high nighttime temperature, low soil temperature, and excessive soil moisture, can all cause insufficient carbohydrates in the plant. Excessive or one-sided application of nitrogen fertilizer, especially when ammonium nitrogen is in excess, as well as deficiency of potassium, boron, and other trace elements, can also lower the ratio of carbohydrates to nitrogen in the plant. In addition, excessive irrigation, moist soil, and poor permeability all hinder the tomato plant's root system from absorbing nutrients, causing an imbalance of nutrients in the plant and obstructing the absorption and translocation of iron, which is also a cause of brown stem rot fruit. For example, in 2005, several greenhouses in Tieling Village, Mucheng District, due to low-lying terrain close to the riverbank, poor drainage inside the greenhouses, and heavy clay soil, the plants could not absorb nutrients, leading to browning of young tomato fruit; in the autumn of 2006, a greenhouse in Lixin Village, due to overly dense planting and too many fruits retained, the fruits competed with each other for nutrients, and some tomato fruits colored unevenly with hollow, browned flesh. The cause of white stem rot fruit is related to the above to some extent, but it is mainly due to the action of toxins produced after infection by tobacco mosaic virus.
Cause: The causes of tomato stem rot fruit are very complex. Preliminary analysis suggests that insufficient carbohydrates in the tomato plant and a decline in the carbon-to-nitrogen ratio cause metabolic disorder, leading to lignification of the vascular bundles, which is the direct cause of the disease. Many adverse environmental conditions, such as insufficient light, low temperature and high humidity, poor air circulation, insufficient carbon dioxide, high nighttime temperature, low soil temperature, and excessive soil moisture, can all cause insufficient carbohydrates in the plant. Excessive or one-sided application of nitrogen fertilizer, especially when ammonium nitrogen is in excess, as well as deficiency of potassium, boron, and other trace elements, can also lower the ratio of carbohydrates to nitrogen in the plant. In addition, excessive irrigation, moist soil, and poor permeability all hinder the tomato plant's root system from absorbing nutrients, causing an imbalance of nutrients in the plant and obstructing the absorption and translocation of iron, which is also a cause of brown stem rot fruit. For example, in 2005, several greenhouses in Tieling Village, Mucheng District, due to low-lying terrain close to the riverbank, poor drainage inside the greenhouses, and heavy clay soil, the plants could not absorb nutrients, leading to browning of young tomato fruit; in the autumn of 2006, a greenhouse in Lixin Village, due to overly dense planting and too many fruits retained, the fruits competed with each other for nutrients, and some tomato fruits colored unevenly with hollow, browned flesh. The cause of white stem rot fruit is related to the above to some extent, but it is mainly due to the action of toxins produced after infection by tobacco mosaic virus.