Why Does My Basil Look Unhealthy?

Are there any circular to irregular dark spots on leaves with light centers?

Do the leaves have pale areas on upper surfaces and "downy" patches underneath?

Are there any yellow and wilting leaves, brown streaks appear on a lower surface of leaves, the growth is stunted?

Are the stems and leaves covered with gray mold, stems are soft, may be rotted?

Are there any small translucent spots on leaves, spots later turn black?

Do the leaves have large, ragged holes in them?

Are the leaves curled and yellow?

Are the terminal clusters eaten, leaves skeletonized, seedlings may be cut at the soil line?

Are the leaves skeletonized, metallic green-bronze beetles present?

Do the leaves have wandering, white or translucent tunnels in them?

Is the plant stunted, leaves yellowed and the roots have lesions on them?

These symptoms indicate a fungal disease - Cercospora leaf spot. This fungal disease only occurs in very warm climates. Spots develop a “frog-eye” appearance with light centers and dark edges. Spray plants with copper as soon as symptoms appear to prevent further symptom development.

Pale areas on upper surfaces of the leaves and "downy" patches underneath are caused by Downy mildew. This fungus spreads quickly during cool, wet nights and warm, humid days. Leaves will wilt and die. Remove and destroy all affected plant parts and encourage good air circulation around plants by thining them. Water plants early in the morning to make sure they dry before nightfall.

Fusarium wilt is a fungal disease that causes these symptoms in basil. High soil temperatures favor the disease emergence. Use only disease-free seed. Treat seeds with hot water to kill fungi before planting. If the fungus is present in the field, rotate crop every 2-3 years with crop other than basil or mint.

Gray mold on stems and leaves, followed by rotted stems are symptoms that indicate a fungal disease - Botrytis blight. Other symptoms include brown to black spots that may appear on leaves and petals. You can only prevent Botrytis blight disease by planting in areas with good air circulation. Avoid working in the field in rainy conditions. Water plants sparsely. Infected plants should be removed.

Bacterial leaf spot causes circular translucent spots scattered over the leaf surface. These spots turn brownish-black and may spread to form large patches of dead tissue. To prevent the spread of this disease, avoid working around wet plants. Remove and destroy affected parts. Spray Bordeaux mix on remaining plants.

Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves usually 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.

Distorted, 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.

Various caterpillars will feed on basil. The most prominent ones are cutworms, loopers, owlet moths, and underwings. Handpick and destroy caterpillars, or spray plants with BTK if caterpillars are feeding. Good preventive is covering the seedlings with row cover.

Skeletonized leaves are caused by Japanese beetles. Handpick adult beetles into a can of soapy water but make sure to wear gloves as Japanese beetles are blister beetles. Apply parasitic nematodes to the soil to limit beetle grub populations. Use pyrethrin powder or neem oil as a last resort.

These symptoms indicate leafminers. These tiny white, maggotlike larvae feed inside leaves. Prune off and destroy all infested leaves. Cover plants with row cover until flowers open to prevent adults from laying eggs on plants. Certain nematodes can attack leafminer larvae inside leaf tunnels.

These symptoms are caused by root-knot nematodes. Prevent root-knot nematodes by applying chitin or introducing parasitic nematodes to the soil before planting. Another preventative method is fertilizing with fish emulsion diluted in water which is then poured on the soil as a drench. It repels nematodes.

If there are tiny holes in leaves they are caused by Flea beetles. These tiny, black, brown, or bronze beetles hop when disturbed. Prevent problems by covering young plants with row cover. Control severe infestations by spraying or dusting plants with pyrethrin.