5. Insect and Fungal Pests

If proper precautions are taken, house plants should remain fairly free from pests. In the first place, all plants, as soon as they are received, whether from friends, from a nurseryman or a florist's shop, should be thoroughly cleaned. If they are brought into the house in a pest-free state and placed among clean plants, there is not much danger of their becoming infested with many pests.

To ensure that they do not become contaminated with insect pests, the plants should be regularly treated with insecticides.

Sponging and Dipping Leaves

All house plants should have their leaves cleaned at least once a month. This treatment has a tonic effect by removing dust which blocks up the stomata (breathing pores) and by removing insects and their eggs and pupae.

With broad-leaved plants, such as Ficus and palms, sponging is an easy operation, but the foliage of ferns and grasses is too finely divided for this process, and the best treatment is dipping. The plants should be removed to the kitchen sink or other convenient position where a pail or bowl of insecticide can be placed, and the foliage completely immersed in the liquid. Set the plants aside until the leaves are dry enough for the plants to be replaced.

Only one type of insecticide is necessary for sponging and dipping. It can be made by dissolving a handful of soft soap in a pail of warm water, or one of the proprietary articles, such as 'Liquid Quassia' or 'Derris', may be used.

Dipping and sponging will keep the plants free from all the usual household pests, including aphis  (green and black fly), thrips, red spider and mite. Should plants be received which are infested with some of the more pernicious pests, these will require more drastic treatment.

The most difficult pests to deal with are mealy bug and scale insect. Mealy bug is easy to recognise by means of little tufts of white woolly material under which will be found small yellowish-white insects. This woolly material is so impervious to liquids that spraying is useless. The best treatment is to dip a small brush in methylated spirits and dab the white tufts until the insects are well saturated. This treatment leads to instant death of the pest, but it must be followed up with a thorough sponging with one of the materials mentioned above, to ensure complete freedom from these insects.

The scale insects are so called because of the scaly nature of their covering which is of somewhat similar shape to the shell of a limpet. Spraying with an insecticide is useless because their outer coats are impervious to liquids. When these pests are found adhering to the leaves or stems, they should be dislodged with a match stick or strip of wood. Afterwards the whole plant must be sponged with insecticide to destroy eggs.

Soil Pests

The treatments so far recommended will result in clean healthy foliage, but danger still lurks in the compost.

When potting or top-dressing with new compost, only sterilised material should be used. The simplest method of partial sterilisa­tion is to place the compost in a bucket and set it over a gas ring or other form of heating. The temperature should be raised to no0 F. for 20 minutes during which time the compost should be occasionally stirred. It should then be spread out to cool before use.

Those who have no facilities for this treatment can sterilise the compost by using a proprietary brand of a chemical soil steriliser, such as 'Aldrin' or naphthalene powder. For the destruction of ants, earwigs, woodlice and slugs, special preparations are obtain­able from seed shops.

Fungal Pests

One of the chief fungal diseases is mildew, which covers the leaves and stems with a white felt-like material. Dusting with flowers of sulphur is the best treatment for this. Place a little of this powder in a muslin bag and shake it over the leaves, treating both the upper and lower parts. 'Folosan Dust' can be purchased for the treatment of this and other fungal diseases.

Greenhouse Fumigation

Those who have a greenhouse which is not attached to the dwelling-house can keep it free from most insect pests, such as greenfly and whitefly, by regular fumigation with Murphy's combined B.H.C./D.D.T. smoke fumers. These are very effective and are easy to use. They are set on the floor, and a light is applied to the touch paper, the greenhouse having been previously made as airtight as possible. Finally, the door is closed and locked to prevent unauthorised people from entering. Fumigation is best done in early evening when the temperature stands at not less than 6o° F.; but a temperature of 700 F. is the most effective.

On the following morning, the ventilators should be opened to clear the air of fumes. Some insects will be stupefied and fall down; therefore, the floor should be sprayed with insecticide to ensure that they are destroyed.

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