The zinnias I planted from seeds are growing beautifully and are being eaten by I don’t know what.
is there a remedy?
Zinnias are such cheerful additions to the garden, and it’s fantastic that you grew yours from seed. There are a few insect pests that prey on zinnias. The bugs that cause the most damage to a zinnia plant’s health are aphids, mites and thrips, all of which use their mouths to suck moisture from the leaves and stems of plants. Aphids are easily visible, but mites are very small and harder to spot. Check the stems and the underside of leaves. Thrips are small winged insects whose feces appears as unsightly black spots on the leaves. Other insects that feed on zinnias are whiteflies, leafminers and earwigs. Leafminers chew holes in the leaves of zinnia plants.
It is often possible to remove insects from zinnia leaves with a forceful stream of water. Because zinnias are vulnerable to mildew, you should do this early in the day so that the leaves can dry before nightfall. Pinch off affected leaves and stems, and destroy the foliage. Make sure the area around your plants is free of debris. Insecticidal soap or neem oil can also be effective in killing pests. Your local nursery should be able to help you find the right product.
If you can spot your insect pest, this website includes some good photos that should help you to identify it: https://ipm.ucanr.edu/PMG/GARDEN/FLOWERS/zinnia.html
In general, healthy plants are more resistant to damage by pests and diseases. Your zinnias will thrive best in full sunlight, in well-drained soil, with enough space in between plants for good air circulation.