Orchid Pests

Insects which cause damage to orchids are slugs , snails , cockroaches , grasshoppers, thrips, aphids, bugs and mites. The harm they do to the plants is manifold . They feed on plant parts or suck the sap thereby exhausting the vigour of the plant . They inflict mechanical injuries to the plants , thus leaving the path clear for pathogens like bacteria which can enter the plant only through wounds. These insects, particularly the aphids, act as vectors helping to carry virus infection from one plant to another. Finally they spoil the blooms by carrying away the pollinia which makes the flower wilt within a day or two. Measures should therefore be taken to keep away all insects from orchid house.

A variety of organic insecticides of different killing potentialities are now available in the market ,which help the grower to deal with the pests effectively . Organophosphorous insecticides like Parathion , Malathion etc., chlorinated hydrocarbons like BHC ,Endrin , Aldrin ,Dieldrin etc, and pure plant products like Nicotine are widely in use now . The only disadvantage with these products is that they are as deadly to human beings as they are to insects and if used indiscriminately or without proper precautions, they can cause serious trouble to the person who is administering them .

Slugs, snails and cockroaches hide themselves in the dark corners and crevices of the orchid house . They come out only at night and feed on tender flower shoots and the growing tips of the roots , causing serious set-back in their growth.These organisms can be baited and killed with poisoned food. Metaldehyde has proved to be an effective poison in such cases . This could be kept mixed with honey or syrup . Northern (1970) has recorded that stale beer kept in thimbles at various places in the orchid house attracts the slugs. In the attempt to get a drink they get draowned in the beer . Hollowed out potatoes also serve to trap slugs and snails . Dipping the pots in a solution of the insecticide will help to flush out the cockroaches , but the snails retire to their shells and thus escape from the action of the insecticide . To avoid this, the pots are immersed in a mild solution of the insecticide overnight ,which will flush them out of their shells and kill them.

Grasshoppers fly over from outside and eat up young leaves of plants. Spraying with 10 % BHC will keep away these insects.

Thrips are very small insects, which prefer to lay their eggs on young flower buds. Upon hatching , the young unwinged thrips make their way inside the buds, which sustain injuries during the process . The flowers are disfigured and sometimes they even fail to open. Biweekly spraying with 0.1 % malathion will control this pest.

Bugs and aphids suck the sap from the plants. Some of these are brought in by ants for the honeydew which they secrete . The mealybug is easily identified by its soft , filamentous body with a coating of powdery wax . Spraying with 0. 03%endrin or 0. 02 % of parathion will destroy these nsects.

Among mites , the red spider mite causes the greatest devastation to orchids. They are red, orange or yellow in colour and difficult to see by the naked eye . They colonise on the underside of the leaves and eat up all the parenchymatous tissue. Spraying the underside of the leaves regularly with 0. 1 % malathion will help to get rid of this pest.

Scale insects attach themselves firmly to stems and leaf-veins . They not only extract juives , but also have a toxic effect upon the plant , so that if not controlled , the plant will gradually die. Because of their scales they get protection from the insecticides . Only the crawler stage, which occurs in its life history just after the eggs are hatched and which lasts for 28- 48 hours, is susceptible to insecticides . Hence for effective control, frequent application of the insecticide is necessary . Spraying fish oil soap (1 lb. in 6 gallons of water) or 0.025% of parathion is effective in eradicating this pest.

Holttum (1953) recommends the use of the root extract of Tuba (Derris ) , a plant which is very common in Malaysia , as an insecticide.