Pests and Diseases
Aphids
Aphids are tiny, soft-bodied insects that cluster on new growth and the undersides of leaves. They suck sap from plants, causing leaves to curl, yellow or become distorted. As they feed, they excrete sticky honeydew that encourages sooty mould, and colonies can build quickly in warm weather.
Start with organic controls: blast colonies off with a firm jet of water, encourage beneficial insects like ladybirds and lacewings, and spray neem oil or insecticidal soap to disrupt feeding. Keep plants well watered and avoid excess nitrogen that promotes soft growth. If pressure remains high, selective chemical sprays can be used sparingly, taking care to protect pollinators and beneficials.
Leaf spot
Leaf spot describes several fungal or bacterial diseases that create dark, often round lesions on foliage—sometimes with yellow halos. Severe infections cause premature leaf drop and reduced vigour, especially during warm, wet spells or when leaves stay damp.
Reduce spread by removing infected leaves, watering at the base, and spacing plants for airflow. Mulch to limit soil splash and rotate crops. Organic preventatives include copper and sulfur sprays applied early. If disease escalates, registered fungicides offer a chemical backup.
Powdery mildew
Powdery mildew appears as a white, talc‑like coating on leaves and stems. It thrives in warm days, cool nights, and still air, and can weaken plants by reducing photosynthesis, leading to yellowing and early leaf drop.
Prune for airflow, avoid overhead watering, and remove badly affected foliage. Organic sprays such as milk solution, potassium bicarbonate, sulfur, or neem help suppress outbreaks. Chemical fungicides are effective when started early, but use sparingly to preserve beneficial organisms.
Downy mildew
Downy mildew causes pale yellow blotches on upper leaf surfaces with grey‑purple fuzz beneath, spreading fast in cool, moist weather. Heavily infected leaves collapse, slowing growth and yield.
Choose sunny, well‑ventilated positions, water early so foliage dries quickly, and remove infected leaves promptly. Organic options include copper and bio‑fungicides (phosphorous acid salts). For severe pressure, rotate chemical fungicide modes to prevent resistance.
Slugs & snails
Slugs and snails chew irregular holes in foliage and fruit and can wipe out seedlings overnight, especially in damp, sheltered spots.
Remove hiding places, water in the morning, and use beer traps, boards, or shelters to concentrate and hand‑pick. Copper barriers can deter them. For baits, iron‑based pellets are the safest organic option; use metaldehyde baits cautiously due to risks to pets and wildlife.
Damping off (seedlings)
Damping‑off is a soil‑borne disease that attacks seeds and seedlings, causing poor germination, sudden collapse, or pinched, water‑soaked stems at soil level. It thrives in cool, wet, stagnant conditions.
Sow into fresh, clean seed‑raising mix; avoid reusing contaminated trays. Provide warmth, light, and airflow; water lightly and allow the surface to dry between waterings. A light dusting of cinnamon or chamomile tea is a gentle organic measure; fungicidal drenches are rarely necessary for home growers when hygiene is good.
