Are the seedlings dying?
Are the leaves mottled with yellow, young growth may be narrow and twisted?
Do the leaves have large, ragged holes in them, but there are no visible caterpillars?
Do the plants have wilted leaves and dried stems that don’t respond to watering?
Are the leaves curled and distorted?
If the seedlings are dying the probable cause is a damping-off disease. Damping-off is caused by various soil fungi. Damaged seedlings can't be healed so, the best course of action is to remove them. To prevent damping-off let the soil surface dry between waterings, thin seedlings to avoid overcrowding, and do not add nitrogen fertilizers until plants have developed leaves.
Leaves mottled with yellow usually indicate a Tobacco mosaic virus. There is no cure for viral diseases, remove and destroy infected plants. Presoak seed in 10 percent bleach solution before planting to prevent problems. Control aphids as they are the most likely carriers of the tobacco mosaic virus.
Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves at night. To control slugs and snails use diatomaceous earth around your plants. You can also handpick them during the night or use shallow dishes filled with beer as a trap.
These symptoms could indicate a fungal disease - Rhizoctonia Root Rot. Improve soil drainage by working some compost into the top ten inches. Discard all infected plants. Do not overwater plants. Pot in the pasteurized soil mix. Apply a copper-based fungicide to protect plants.
Distorted and curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.
If the leaves are covered with white, cottony clusters the culprits are mealybugs. These tiny insects are covered with a fluffy white coating. They feed by sucking plants sap. They produce the sticky substance honeydew which makes leaves sticky. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.
Wilen, C., Dimson, M., Plant and Pest Guide - Los Angeles State Historic Park, The University of California, Division of Agriculture and Natural Resources
https://sdorchids.com/culture_docs/epi_article01.htm
Ellis, B. W., Bradley, F. M., & Atthowe, H. (1996). The Organic gardener's handbook of natural insect and disease control: a complete problem-solving guide to keeping your garden & yard healthy without chemicals. Emmaus, Pa.: Rodale Press.
Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/
