EASTER LILIES 17 



after Easter. As an emergency measure, a small retail grower who missed 

 the Easter market could by this method hold many of his blooms for 

 several weeks for use in design work. 



Physiological Disturbances, Insect Pests, and Diseases 



Tip-burn of Leaves. — ^Tip-burn of the leaves is a physiological condition 

 which is brought about by unfavorable cultural conditions such as low 

 humidity, high temperature, and deficient soil moisture. Lilies forced very 

 rapidly under high temperature and humidity are likely to be more sensi- 

 tive to changes in cultural conditions than are plants which, because they 

 were grown more slowly, have a more hardened growth. In extremely 

 cloudy weather the leaves of plants are likely to become filled with water, 

 and with high humidity they are unable to get rid of this excess supply of 

 water. Consequently, when a period of extremely bright weather follows, 

 an abnormal loss of water from the leaves may result and cause leaf tip- 

 burn or injury. The browning of leaf tips can also be caused by fumigants 

 or spray materials. 



When lily plants are fumigated with tobacco or cyanide, the foliage of 

 the plants should be free from moisture and the fumigation should be 

 carried on at a constant or rising rather than a falling temperature. 



Splitting and Blasting of Buds. — Split and blasted buds are attributed to 

 variations in cultural conditions at critical periods in the growth of the 

 plants. Some of the factors that have been suggested are retarded growth, 

 high forcing temperatures with improper humidity, sudden changes in 

 temperature, and also a lack of sufficient roots on the plants to enable them 

 to withstand forcing conditions. In three years of experimental study 

 with lily bulbs only a few plants were observed to have split or blasted 

 buds. Even when plants in diflferent stages of growth were purposely 

 changed from very warm to cool conditions and vice versa, there was no 

 noticeable injurious effect from such treatments. 



Aphids. — Aphids or green fly and bulb mite are the two most common pests 

 of lilies. 



Aphids can be controlled by fumigation with tobacco and by the use of 

 contact insecticides such as nicotine sulfate, pyrethrum, and derris 

 (rotenone) spray materials. Plants should be sprayed early enough in 

 the day to permit the foliage to dry quickly, in order to avoid the danger 

 of foliage injury from the spray. 



Mites.— Mites are usually present to some degree on all lily bulbs, but the 

 amount of injury to the bulbs depends upon their abundance. The wounds 

 made by mites feeding on the scales, particularly near the basal plate, 

 generally result in the destruction of the root system of the plants. In 

 severe infestations mites often tunnel up through the stem from the base, 

 stunting the growth and causing the stems to break ofT or rot near the 

 soil (Figure 3). 



Frequently the feeding of mites on bulbs results in wounds which in 

 turn are attacked by fungi and bacteria, generally causing the bulbs to rot. 



Mites are most active under conditions of high humidity and temper- 

 atures of 60°-80° F. Under cool temperature conditions the mites become 

 less active but are able to survive the unfavorable environment by chang- 

 ing into a resistant form known as tlie hypopus stage. 



