Under normal circumstances pests on houseplants are not a major problem.
Plants that are properly cared for – with the right potting mix, regular feeding and a suitable environment – are in most cases strong and resistant, and rarely get sick.
Even so, pests can appear on these plants too. When they do, you need to act as quickly as possible.
Some pests always appear seasonally, in spring and summer, because they multiply faster in warmer weather. An aphid starts reproducing when it is just one week old. Over the month of its life it can produce 10 young a day – some 200 offspring in total.
Plants attacked by pests far more often are mostly those with very delicate leaves, such as hollyhock, bougainvillea or cineraria. Pests looking for plant sap can penetrate the thin tissue more easily.
Rubber plants, peperomias and cacti, like other plants with stiff leaves, are attacked less often. That does not mean they are safe from mealybugs, scale insects, thrips and other insects. Their advantage is that pests are easier to spot on stiff leaves. Weak leaves often twist or curl and hide the pests. If we find them in time, controlling them is much easier.
If we discover pests early enough, right when they first appear, there is a good chance of getting rid of them completely. A simple remedy is often enough: rinsing the plant thoroughly under the shower with room-temperature water. An even better effect can be achieved by spraying with water to which a little milk or oil has been added. Both will also make the leaves cleaner and more attractive.
An infested plant should be taken off the windowsill and isolated so that the other plants are not attacked. In the isolated spot we can start fighting the pests. Examine the plant carefully, identify the pests and assess the damage, then choose the remedy that will bring the quickest improvement. During treatment it is a good idea to check that the healthy plants have not been attacked.
Professional growers have been fighting pests in their greenhouses with biological methods for many years. For some time now, amateurs have also been able to use this form of pest control with good results. Various companies have started producing "anti-insects" for private use. For a single houseplant, however, this method is too expensive.
For conservatories and greenhouses, and for keen gardeners with lots of plants, it may well pay off.
The aim of biological control is to fight pests with their natural enemies. The best results are achieved when the natural enemies are released at eight-day intervals. Beneficial insects die when there are no more pests or other food available.
The following pests can be controlled biologically: - aphids with aphid predators (aphid midges)
- spider mites and thrips with predatory mites
- whitefly with parasitic wasps.