Swiss Chard and Spinach – mottled young leaves that curl and wrinkle, then turn tan/yellow.
- Answer: Beet leaf miner damage
- Remedy: Remove damaged leaves quickly and do not compost. You can eat any undamaged leaves. Since larvae feed inside the leaves, sprays are not effective. Next year, rotate this crop and cover young seedlings with row covers to exclude the adult fly that lays its eggs early on these leafy crops.
Heliopsis – upper stems covered with large red aphids
- Answer: Dry soil and lack of air circulation encourage this pest/plant combination.
- Remedy: Topdress your plants with compost this fall! Rub stems with a paper towel sprayed with Safer’s Insecticidal Soap to remove aphids. Beware of spraying this solution if temperatures are above 80 degrees – you will burn the plant! For longer-term control, plant aromatic companions such as lemon balm, dill, fennel, or yarrow nearby.
Basil – powdery grey substance beneath leaves, dark streaks on stems, yellowing leaves
- Answer: Powdery mildew, usually found on plants purchased at large greenhouses
- Remedy: Discard plants. Try sowing your own seeds in fresh potting soil, as they germinate quickly in hot weather. Be careful of your watering regime – mulch plants, even potted ones, and do not let water splash up onto leaves. For a complete resource, the University of Maryland Extension has this link: https://extension.umd.edu/resource/downy-mildew-basil