When to water, fertilize and prune basil. Identify and treat the most common diseases and insects like downy Mildew, fungal disease and thrips

Like all divas, basil will perform better when properly cared for. Don’t worry, the exquisite taste of these wonderful leaves will make everything worthwhile!

Plant care

In reality, basil plants are not very demanding, but they do require some care and weekly monitoring.

Watering

Basil plants do not like soggy soil, but they do require a lot of water. Keep the soil moist and water every day (container plants especially) unless of course it is raining. Mulch around the plants with straw to retain moisture. Water the base of plants and not their leaves since damp leaves can lead to the development of fungi. For the same reason, watering is best done early in the morning.

Fertilizer

Fertilize once per month by adding liquid seaweed fertiliser or fish emulsion fertilizer to your water before watering. Follow directions.

Pruning

Basil plants: disease and insect control and general care

Pinch back the growing tips of plants (growing on top of at least two pairs of leaves) to encourage the growth of new shoots. Keep plants from going to flower by pinching off the tips of stems when flower buds form. To pinch, simply use your thumbnail and fingernail.

Harvest

Harvest throughout the summer. Pinch leaves from the tips of stems to encourage more branching. Pick your basil immediately before using in order to enjoy maximum freshness and flavour. July and August are prime harvest months for preserving and freezing.

Insects and disease

Basil plants: disease and insect control and general care

Although basil can repel certain insects, it is vulnerable to other insects and disease. The heat and humidity it requires to thrive also favours the growth of fungi and attracts harmful insects. Careful monitoring is a must. Below are the main afflictions affecting basil plants.

Name

Description

Prevention

Treatment

Impatiens Necrotic Spot Virus (INSV)

Virus spread by western flower thrips.

Symptoms: a patchwork of brown necrotic spots; stems are blotched, spotted or mottled.

Early detection is important.

Destroy infested plants. You can try a soap-based anti-aphids treatment or apply an insecticide.

Fusarium wilt

Fungal disease spread by contaminated seeds or soil.

Symptoms: brown streaks on the stems;

stunted and wilted plants with yellowish leaves.

Aeration is important to promote dry leaves. Do not water the leaves. Apply a bio-fungicide as prevention.

No treatment.

Remove and destroy infected plants.

Basil Sunburn

Caused by too much sun and too little water on plants not fully ‘hardened.’

Symptoms:

Yellow leaves with some scorching.

Ensure plants are hardened off before transplanting.

Place affected plants in partial shade or bring the shade to them, particularly during a heat wave.

Pinch off yellow or scorched leaves.

Downy Mildew

Fungal disease,

likely spread through contaminated seeds, infected leaves at the market, or wind-swept spores. Green-leafed basil plants are particularly susceptible.

Symptoms: initially, leaf yellowing, followed by leaf browning. On the underside of leaves, a grey-purple fuzzy material will develop, which looks like a fine layer of dirt.

Aeration is extremely important to promote dry leaves.

Take care to water the base of plants and not the leaves.

Plant in a sunny location with sufficient space between plants.

Apply a bio-fungicide as prevention.

No treatment.

Remove and destroy affected plants.

Gray Mold

Fungal disease.

Symptoms: brown to gray fungal growth on leaves and stems. Poor air conditions, high humidity and cold temperatures are favourable to this disease. Easily spread by handling, splashing water or touching diseased and near-by healthy plants.

Aeration is very important to facilitate dry leaves.

Avoid watering the leaves.

Apply bio-fungicide as prevention.

No treatment.

Remove and destroy affected plants.

Thrips

Tiny insects active at night. They damage plants by sucking out juices and by transmitting viruses (such as INSV).

Symptoms: irregular patches of silvery tissue on leaves. Leaves may turn pale and splotchy before dying.

Reduce the places where thrips might breed: clean up plant debris on the ground and clear around the garden (dry mulch will not attract thrips but green mulch will).

Introduce beneficial insects; earwigs, ladybugs, and pirate bugs are efficient predators.

Destroy affected plants.

Try a soap-based anti-aphids treatment or treat with a natural contact insecticide.

Do not throw plants or parts of plants infested with fungi or harmful insects into the compost; you will ruin the compost for future use. Instead, destroy plants by burning them.