Post category: Plant defences
The outer surface of a plant – bark, skin or wax layer – is the main line of defence. If this is damaged, and the plant is too weak to heal the injury, fungi, bacteria and viruses can get in. When the outer defences are breached, plants react by producing natural chemicals that inhibit fungal and bacterial growth.
The plant’s ability to make these defensive chemicals depends on its state of health. Weak plants, growing in unsuitable conditions, are less able to defend themselves, and therefore more likely to suffer disease, and this can be very commonly observed in gardens. Strong vigorous plants with balanced growth are very good at warding off disease attacks.
Many diseases are specific to the plants they attack, other plants being resistant. Some varieties of a particular plant have resistance to certain diseases. In some cases, plants have been bred specifically for disease resistance. For instance, most modern tomato varieties are resistant to tomato mosaic virus and leaf mould, formerly both serious diseases of greenhouse tomatoes.