It can be frustrating to have the tomato plants you’ve babied for the last couple months start to show signs of potential trouble. Before reaching for a pesticide, identify the cause. Many tomato problems are related to weather, watering, or nutrition – not insects or diseases. Healthy soil, consistent irrigation, and good air circulation are the best defense against most tomato troubles. The table below includes some of the more common ones:
| Symptom | Likely Cause |
| Lower leaves turn yellow first | Normal aging or nitrogen deficiency |
| Leaf edges turn yellow, then brown | Inconsistent watering or potassium deficiency |
| Brown, crispy leaf margins | Heat or drought stress |
| Leaves curl upward | Heat stress, water stress, or normal response to hot weather |
| Entire plant wilts during the day but recovers at night | Temporary heat stress or insufficient soil moisture |
| Yellowing begins after heavy watering | Poor drainage or overwatering |