What Causes Green Tomatoes To Rot On The Vine

As much as tomatoes are loved across the world, they are also susceptible to a number of problems. Though they are commonly grown in many vegetable gardens, achieving those plump, juicy red fruits, free from blemishes, isn’t easy. 

Just when you start thinking those tiny green tomatoes will grow into beautiful red fruits you can bite into, they start to rot! So what causes green tomatoes to rot on the vine, and is there anything you can do to fix it? Continue reading and you’ll find out everything you need to know.

What Causes Green Tomatoes To Rot On The Vine

Possible Causes Of Rotting In Green Tomatoes

If green tomatoes are rotting on the vine, there could be a number of possible reasons that could be linked to the symptom. Investigate the problem further to see if any of the following diseases is causing it. 

Blossom End Rot

Quite often, the reason for rotting in immature tomatoes is blossom end rot. Though it looks like a disease, the problem is, in fact, a physiological disorder that occurs due to the imbalance of calcium in tomato plants. 

It typically affects the crop when the weather is wet at the start of the growing season and becomes dry when the fruit starts to set. Other than drastic fluctuations in soil moisture, excess nitrogen, root damage, or an unsuitable soil pH may also interfere with the plant’s ability to absorb adequate calcium, resulting in blossom end rot. 

Symptoms generally begin when the fruits are green and half their mature size. It appears as small water soaked spots on the bottom of the fruit that enlarge into lesions that can cover as much as half of the fruit. As the fruit ripens, the lesions grow darker until they are black, leathery and flat. 

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Prevent nutrient deficiencies by regularly feeding with low-nitrogen fertilizers and maintain consistent levels of soil moisture throughout the growing season. Don’t be tempted to start your tomato crop early in spring. Wait until the soil temperature is at least 60°F before setting the seedlings in the soil to reduce the chances of blossom end rot. 

Early Blight

Early blight is a common disease that infects tomato plants, and is caused by the fungus Alternaria solani. It typically attacks older plants, but can also occur in seedlings. The fungal spores can overwinter in the soil or plant debris and attack the crop when the weather is favorable. The pathogen is usually more active in damp conditions. It may also spread through seeds and seedlings, which is why it’s important to purchase these from a reputable retailer. The plant becomes weak as a result of the disease and the yield will be much lower than expected. 

Symptoms appear on the entire plant, including stems, leaves and fruits. The disease begins with spots appearing on older leaves that turn darker and develop concentric rings as the disease progresses. There may be a yellow halo around the spots. The disease can affect both green and ripe tomatoes. Spots appear on the stem end of the fruit and develop darker, leathery and sunken. Concentric rings are usually visible on the spots. 

If the disease is limited to a single plant, removing the plant is the best solution. It will prevent it from spreading to the nearby plants. Maintain sufficient spacing between the plants to improve air circulation and prevent damp conditions. Choose certified seeds or seedlings and rotate crops to prevent the problem in the coming seasons. 

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Fusarium Wilt

Fusarium wilt is a soil-borne disease caused by the fungus Fusarium oxysporumsp. Lycopersici. The pathogen is most active in the soil that’s high in nitrogen and lacks potassium. It’s also more likely to infect tomatoes grown in sandy soils. The disease prefers warm weather, with temperatures ranging between 80 and 90°F. The fungi enters the plant through the root system and then spreads upwards along the stems. 

The symptoms appear as yellowing of foliage that’s usually limited to one side of the plant. If you cut through the crosssection of the infected branches, you’ll find brown streaks. The disease blocks the water and mineral transport from the roots to the other parts of the plant, and the entire plant starts wilting as a result. Little or no fruit develops on the infected plants. For the fruits that do develop, look for white mycelium around the stem end. 

Fusarium wilt cannot be cured. Removing the infected plants from the garden and sterilizing the soil can help control further spread. Soil replacement is also a good strategy to prevent fusarium wilt in future crops. If there has been a history of the disease in your garden, grow resistant varieties. Varieties with an “F” on the label are resistant to fusarium wilt.  

Late Blight

Late blight is a devastating disease in tomatoes, and affects the entire plant, including the stems, leaves and fruits. If left untreated, it spreads quickly and can result in a complete crop failure. It is caused by fungus-like pathogens, Phytophthora infestans, that occur in different types of strains.

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It initially appears as irregular shaped water-soaked spots on younger leaves. The lesions enlarge to cover the entire leaf, resulting in wilting and dying of the leaf. Soon, the entire plant starts to wilt. The disease can attack the fruit in any stage of development and creates dark brown, circular spots that enlarge to cover most of the fruit. These spots are usually firm and leathery, but may turn mushy if secondary bacteria attacks the fruit. 

Once a plant is infected, little can be done to cure it. Remove the infected plants followed by weekly fungicidal sprays on the remaining plants to manage the disease. Plant resistant varieties so you don’t have to worry about late blight infections. 

Conclusion 

Now that you know what causes green tomatoes to rot on the vine, make sure you manage the problem suitably to control the effects. Good gardening practices can prevent such problems in the future.

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