18 MASS. EXPERIMENT STATION BULLETIN 376 



Some control is afforded by dipping the bulbs for 10 to 15 minutes in 

 40 percent nicotine sulfate, diluted at the rate of 1-400 which is equal to 

 1 ounce in 3 gallons of water. This treatment is reliable only in cases of 

 light infestation of mites. If bulbs are relatively heavily infested, the 

 most effective control measure is to immerse them in hot water at a 

 temperature of 122° F. for 10 minutes. Lily bulbs should be examined 

 carefully for pests or diseases and necessary treatments made before 

 planting. 



Mosaic. — The most common disease of Easter lilies is mosaic, so named be- 

 cause of the mottled or chlorotic color pattern produced on the leaves of 

 infected plants (Figure 3). A certain amount of this disease generally 

 appears in most lilies but L. speciosum, auratum, fonnosuiii, and longMorum 

 giganteum are most commonly affected. 



The causal factor of lily mosaic as well as that of most virus diseases 

 of plants has not been clearly determined. It has been suggested that the 

 virus diseases are chemical or hereditary in nature rather than pathological. 

 The term '"virus" is used to designate those diseases causing mosaic or 

 yellows. 



Symptoms of mosaic disease in lily plants may appear as a chlorotic or 

 mottled condition of the foliage, curled or twisted leaves, blindness, and 

 a dwarfing or stunting of the whole plant. Flower buds may be split or 

 distorted in shape or may fail to open. 



A very virulent form of mosaic is known as yellow fiat disease (3). This 

 stunts the growth, curls or twists the leaves, and gives a flat rosette-like 

 appearance to the plants. 



Mosaic is spread from plant to plant by aphids, and infection which 

 occurs in the field is transmitted to the bulbs. So far as is known, the 

 virus which causes lily mosaic is similar to the one causing aster yellows 

 in that the virus must pass some time in the body of an insect before it 

 can be transmitted to a healthy plant. Certain types of mosaic disease of 

 tomatoes and tobacco can be transmitted from one plant to another 

 mechanically during such operations as pinching and pruning of the plants. 

 Mosaic disease of lilies is seldom spread to any degree under greenhouse 

 forcing conditions, particularly if insect infestations are promptly and 

 properly controlled. However, when lily plants growing close together in 

 the greenhouse become heavily infested with insects, the mosaic disease 

 can be readily transmitted by the insects from one plant to another. 



Bulbs infected with mosaic do not generally show external symptoms 

 sufficiently distinct to differentiate those that are diseased from those that 

 are not. Tilford (13) and Ogilvie (8) state that bulbs infected with the 

 yellow flat disease may be smaller than normal, flat, compact in shape, 

 and inclined to split. As a rule, the loss of lily plants from mosaic disease 

 under forcing conditions is relatively low. In fact, the average losses due 

 to insects, diseases, and unfavorable growing conditions may be conserv- 

 atively estimated at only 3 to 5 percent. 



