630 Bulletin 319 



cooler the plants can be kept while growing, the stronger and healthier 

 they will be. In this way the natural outdoor spring conditions are 

 approximated. 



When the flower buds can be felt in the tips of the growing stems, the 

 temperature should be raised 1° a night until 50° is attained, which is 

 the proper temperature during December, January, and February. From 

 about the end of February on, a night temperature of 48° is better. On 

 bright days a rise of 10° or even 15° may be given. On cloudy days 55° 

 is high enough, for higher temperatures promote soft, succulent growth 

 that wilts when the sun comes out. Plenty of ventilation should be 

 provided at every opportunity, as this, with careful regulation of temper- 

 ature, causes a firm growth. 



Insects 



Sweet peas are especially subject to attack by the red spider, but unless 

 the plants are too near heated pipes such attacks do not often occur 

 except in the fall months. The careful use of water after the plants have 

 attained a height of a few inches will eradicate this pest. 



The common enemy of greenhouse plants, the green fly, attacks sweet 

 peas from the time they appear above ground. These insects can soon 

 destroy the young plants, as well as weaken the plants at any stage. 

 Fumigation should be attended to carefully, the grower choosing cool 

 nights or performing the work early in the morning; the chief object' being 

 to clear the plants thoroughly by regular and persistent fumigation so 

 that they will not need fumigating when in bloom, as the odor is objection- 

 able and injures the sale of the flowers. Tobacco also bleaches the flowers 

 of some varieties. In the spring, when spraying plants with nicotine 

 for green fly or for thrips, use this insecticide carefully as sweet peas 

 are subject to injury from it. A nicotine preparation containing forty 

 per cent of the constituent nicotine, used at the rate of two teaspoon- 

 fuls to each gallon of water, will kill the thrips that are hit by the spray. 



Climbing cutworms and snails, if present in greenhouses, will destroy 

 sweet peas. The former insects, which attack also carnations, violets, 

 and chrysanthemums under glass, are combated by using compost that 

 has not been covered by a rank growth of weeds and grass. When their 

 work is noticed a search should be made for the worms under any mulch 

 or lumps of earth on the bench, v/here they are coiled up during the day. 

 They may also be picked from the plants at night while feeding. The 

 use of poisoned baits is also recommended; among the best of these is 

 the bran-arsenic mash, made by mixing one part white arsenic, one part 

 sugar, and six parts bran, with sufficient water to form a mash. This 

 may be placed among the plants. Snails can be controlled by the appli- 

 cation of lime and soot to the surface of the beds or benches. 



