Pests, Diseases, and Disorders
Herbs are prone to the same ailments as other garden plants, but herbs require
careful treatment if grown for culinary or medicinal use. For this reason, organic
cultivation is favored by many herb gardeners. Ventilation and hygiene are
particularly important under glass. Keep fungal diseases at bay by regularly
removing dead leaves and flowers, and use sticky traps to catch flying pests
before temperatures are high enough to introduce biological controls. When
spraying is necessary, use only safe contact insecticides recommended by
suppliers of biological controls, and follow instructions carefully. Soak pots
brought under glass with a biological solution to control any slugs and snails.
- Aphids
- Control aphids with insecticidal soft soaps, or direct a strong, fine
stream of water onto the infested parts to knock aphids off the herbs.
- Gray mold (Botrytis)
- Soft leaves and flowers are prone to gray mold under glass. Allow ample space
between herbs and ventilate well. Remove dead material and discard infected plants.
- Leaf miners
- The larvae of various flies, moths, and beetles mine through leaves. To control,
remove and destroy any affected leaves, and spray the herbs with water.
- Spider mites
- This pest thrives in hot and dry conditions. Remove any webs on leaves, spray with
water and insecticidal soap; or introduce Phytoseiulus, a predatory mite.
- Rusts
- Patches of rust appear in poor air circulation and high humidity. Give herbs
ample space and ventilation. Discard infected herbs, and do not replant same species.
- Whitefly
- In low temperatures, increase air circulation, hang sticky traps, and
spray with insecticidal soap. Under glass, introduce Encarsia, a parasitic wasp.
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