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.
Crown / root rot (Wet)
Crown and root rots are caused by water‑loving fungi that attack stems at the soil line and roots below. Plants yellow, wilt, and eventually collapse because their roots can no longer supply water and nutrients—most common in heavy, waterlogged soils.
Prevention is key: improve drainage, raise beds, and water deeply but less often. Avoid injuring stems at the soil line and rotate away from affected beds. Solarising soil in summer can knock back pathogens. Chemical drenches have limited benefit in home gardens and are best used preventatively rather than curatively.
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.
Two-spotted spider mites
Two‑spotted spider mites are tiny sap‑suckers that stipple leaves, causing a speckled, yellow look and fine webbing—worst in hot, dry conditions. Unchecked, plants can defoliate.
Increase humidity around plants, hose undersides of leaves, and release or encourage predatory mites. Neem and horticultural oils suppress populations organically. Miticides exist for heavy outbreaks; rotate actives to reduce resistance.
Whiteflies
Whiteflies can affect plant health and yields in home gardens. Typical symptoms include slowed growth, discolouration, and reduced productivity, often triggered by weather, nutrition, or cultural conditions.
Start with cultural fixes: rotate crops, improve soil with compost, water consistently, and choose resistant varieties. Organic sprays or amendments can reduce severity; chemical options are a last resort and should be used carefully and in accordance with labels.
Root-knot nematodes
Root-knot nematodes can affect plant health and yields in home gardens. Typical symptoms include slowed growth, discolouration, and reduced productivity, often triggered by weather, nutrition, or cultural conditions.
Start with cultural fixes: rotate crops, improve soil with compost, water consistently, and choose resistant varieties. Organic sprays or amendments can reduce severity; chemical options are a last resort and should be used carefully and in accordance with labels.
Bacterial spot / blight
Bacterial spot / blight can affect plant health and yields in home gardens. Typical symptoms include slowed growth, discolouration, and reduced productivity, often triggered by weather, nutrition, or cultural conditions.
Start with cultural fixes: rotate crops, improve soil with compost, water consistently, and choose resistant varieties. Organic sprays or amendments can reduce severity; chemical options are a last resort and should be used carefully and in accordance with labels.
Blossom end rot (calcium/irregular watering)
Blossom end rot shows as a sunken, leathery black patch at the blossom end of tomatoes, capsicums, and squash. It’s a physiological disorder linked to inconsistent watering and poor calcium movement in the plant, not a pathogen.
Keep soil moisture even with deep, regular watering and mulch; avoid swings between dry and saturated. Do not over‑fertilise with nitrogen. Calcium sprays may help new fruit, but consistency in watering is the main fix.
Broad / russet mites
Two‑spotted spider mites are tiny sap‑suckers that stipple leaves, causing a speckled, yellow look and fine webbing—worst in hot, dry conditions. Unchecked, plants can defoliate.
Increase humidity around plants, hose undersides of leaves, and release or encourage predatory mites. Neem and horticultural oils suppress populations organically. Miticides exist for heavy outbreaks; rotate actives to reduce resistance.
Viral diseases (mosaics, TSWV, etc.)
Viral diseases (mosaics, TSWV, etc.) can affect plant health and yields in home gardens. Typical symptoms include slowed growth, discolouration, and reduced productivity, often triggered by weather, nutrition, or cultural conditions.
Start with cultural fixes: rotate crops, improve soil with compost, water consistently, and choose resistant varieties. Organic sprays or amendments can reduce severity; chemical options are a last resort and should be used carefully and in accordance with labels.
