Tomato plants turning yellow is commonly caused by several factors including nutrient deficiencies (especially nitrogen, magnesium, or iron), improper watering (overwatering or underwatering), environmental stress (such as extreme temperatures, poor soil drainage, or inadequate sunlight), and diseases or pests (like fungal infections or insect damage).
Nutrient Deficiencies
- Nitrogen deficiency often causes overall yellowing beginning in older leaves.
- Magnesium deficiency leads to yellowing between leaf veins.
- Iron deficiency typically shows yellowing on younger leaves.
- Poor soil quality can worsen these deficiencies by limiting nutrient uptake.
Watering Issues
- Overwatering can saturate soil, depriving roots of oxygen and causing root rot.
- Underwatering leads to dehydration and poor nutrient absorption.
- Both conditions result in yellowing leaves and weakened plant health.
Environmental Stress
- Cold stress, extreme temperatures, poor soil drainage, and too much direct sunlight can cause yellow leaves.
- Salt buildup in container soil can also damage roots and induce yellowing.
Diseases and Pests
- Fungal diseases like early blight and fusarium wilt cause yellow spots that spread and may lead to leaf drop.
- Pests such as aphids and whiteflies can sap nutrients resulting in yellowing leaves.
Correct diagnosis and treatment involve checking nutrient levels, adjusting watering practices, ensuring good soil drainage and sunlight, and managing diseases and pests promptly. Fertilizing with balanced nutrients or supplements like Epsom salts for magnesium deficiency can help, as well as removing infected leaves if disease is present.
