130 GREENHOUSE MANAGEMENT. 



DISEASES, INSECTS AND OTHER ENEMIES. 



The "rot" and "spot" are among the worst diseases 

 of the orchid. The former is caused by a superabundance 

 of water at the roots, and the method of prevention is 

 plain. If rot appears, the diseased portion should be 

 cut away. Spot is most troublesome when rotting ma- 

 nure, or similar material, is placed at the roots, 

 although a sour compost, or overwatering, brings it on, 

 especially if the house is kept closed. 



Slugs are among the worst enemies that the orchid 

 grower has to contend with, as they sometimes eat off 

 the soft flower stalks, and destroy the points of the new 

 roots. They can be trapped by placing sliced potatoes 

 on the benches, and the same thing will attract snails, 

 wood lice, and roaches, although molasses and some form 

 of poison is used for the last two. It is always safe to 

 place a little cotton batting around the base of the flower 

 stalk, to protect it from its enemies. 



Various scale insects are also frequently trouble- 

 some, and for these, as well as for mealy bugs, thrips, 

 red spiders and similar insects, some insecticidal wash, 

 as whale-oil soap, should be used. Strong tobacco water 

 will also be quite effectual, as will fir tree oil. Kero- 

 sene emulsion will also destroy the insects, and, if prop- 

 erly prepared, will not injure the plants, although after 

 a few hours it is well to wash it off. The other insects 

 that attack orchids are the same as are troublesome to a 

 great variety of plants, and similar remedies should be 

 used. 



