Practical advice: plant parasite causes and solutions

Before uprooting a diseased plant or resorting to an insecticide or fungicide, correctly identify the problem in order to choose an appropriate solution. Here are some tips that will come in very handy when diagnosing them.

Parasites and diseases are often a sign of a more general problem. Healthy plants rarely succumb to it, so it is important to ensure that their environment suits them.

Is the plant getting enough light?

• If this is not the case, you have three options: prune the plants that surround it, move it, or replace it with another plant more suited to the location.
• Plants with long stems and lush foliage usually need more light.

Is it getting too much water?

Many plants need the moisture to evaporate between watering sessions.

Does it need more water?

When it comes to watering, it's important to find the right balance. You can estimate the amount of moisture in soil or potting soil by pushing your finger a few centimetres below the surface.

Has it been neglected?

Find it a more accessible location, replace it or set yourself a reminder.

Does it need fertilizer?

• To grow, a plant needs to receive the right nutrients. Select a suitable fertilizer: some plants prefer universal fertilizer, others need a fertilizer specifically designed to stimulate the growth of leaves, flowers or fruit.
• Apply the required dose: an excess of fertilizer will not have any greater effect on the growth or on the health of the plant. Be sure to follow the manufacturer's instructions.

• Learn to better recognize the ailments affecting your plants or go to a garden centre with a sample of the plant and ask a professional to help you identify the disease.
• There are also comprehensive books on pests and diseases.
• The following table may also be useful to detect the origin of ailments that the plant is suffering from.

Possible causes of the problem

• Irregular holes, gnawed leaves; black droppings
• Caterpillars, deformed leaves, silvery-coloured sinuous lines
• Thrips; nutrient deficiencies
• Spotted leaves; tiny cobwebs
• Spider mites and red spiders
• Flower buds fall before they bloom; brown markings on the petals
• Fungus
• Plant stunted and withered
• Soil fungus
• Plant stunted; leaves yellowed and spotted
• Common mosaic
• Brown powdery pustules orange under leaves
• Rust (fungal disease)
• Sticky leaves, black "soot" and ants
• Sooty mold (fungus) grows on the honeydew secreted by aphids and scale insects. Insects are the cause of the problem, the fungus and ants are the symptom
• Buds remain closed; leaves twisted and deformed
• Aphids