1- The redot: reaches the indoor amaryllis (Hippeastrum). Leaves and stems stain with bright red cracks, deform and die. Only treatment with maneb (dithiocarbamate) can stop this disease, often present in the bulbs upon purchase. Act at the first symptoms.
2- The crown rot: common on Cape violets and cyclamen, is favored by excessive watering. It is usually too late to act when she declares herself. To prevent it, make sure to water these plants only by soaking the base of the pot.
3- Rust: it affects many ferns. Linked to a too dry atmosphere, it is fought by a drenching of foliage and / or the use of a humidifier.
4- The necrosis of the stems: it is frequent on dracaenas, yuccas and cordylines, and on various succulents. Discreet, it develops under the epidermis, usually towards the base of the plant. It is revealed by a general collapse of the plant, or even by the fall of the stem, which bends. The affected part, soft and sticky, is smelly. Essentially of bacterial origin, this condition is not sensitive to treatment. The prone plants end happily easily. Cut over the diseased area, into healthy tissue, and let it dry. Throw the stump. After a few days, cut the healthy stem in a very light new substrate, kept barely fresh. Afterwards, be sure to maintain regular watering, but modest, and repot your plants regularly.
B- The parasites:
Whiteflies (or white flies) clump on the underside of leaves. Affected parts prick, then deform and dry. Suitable insecticides are quite toxic and of modest efficiency. Integrated pest management, with a specific predator, is especially possible in the greenhouse. Most are favored by a dry atmosphere, that will fight a humidifier or regular ponding. If you own a garden, take your boarders out in the summer. Rain, birds and some insects will fight for you. The main parasites are:
1 – Red spiders nibble the tender cells of the leaves, which become discolored. Some mites – but difficult to tame – devour them. Again, it is drenching that gives the best results.
2- Mealybugs settle on leathery leaves (ficus …) or along the stems. The treatments are effective, but use with caution.
3- The thrips, microscopic, cause a silvery discoloration of the leaves, very characteristic. Gentle, water-based, or stronger treatments (various treatments) are possible.
4- Slugs: a single application of specific baits is usually enough to stop the invasion.