25 



Dr. I*'crnal(l advises fumigating at intervals of alxjiit two 

 weeks, keeping this up as long as the fly is present, as one fumi- 

 gation does not kill all stages of the insect. Three fumigations, 

 however, if ])roperly made, should practically exterminate it. 



It should be rememl)ered that cyanide of i)otassiuni is a 

 \ irulent poison, and that breathing the gas would be fatal. The 

 lu)use must be thoroughl}' aired before it is re-entered. 



BURN OR SCALD 



A disease known as burn or scald, wliich is of rare occur- 

 rence, is characterized by a wilting and drying up of leaves of 

 ti)mato plants. \\'. C. Sturgis and S. W. Johnson^ have given 

 a description of this trouble as it occurred in the Connecticut 

 Station greenhouse, and they attribute it, as do also B. T. (lallo- 

 way and L. H. Bailey, to burning resulting from sudden exposure 

 to bright sunshine after a period of cloudy weather, or to in- 

 sufficient water supply to the roots, especially when plants have 

 been accustomed to warm, moist air and plenty of water. It 

 may be noted that similar troubles often affect cucumbers and 

 lettuce under glass (topburn, etc.). These may be. brouglit 

 about in dift'erent ways; for example, by maintaining a roo higli 

 night temperature during cloudy weather. Plants grown under 

 optimum temperature conditions in properly lighted and venti- 

 lated houses, especially where attention has been given to their 

 care during cloudy weather, are not likely to be affecterl with 

 this trouble, inasmuch as such troubles occur only when condi- 

 tions are in marked degree abnormal. 



HOLLOW STEM 



P. H. Rolfs^ mentions this trouble as occurring in Florida. 

 Plants suffer from this disorder immediately after being set out 

 from the seed-bed, whether they be only a few inches high or 

 eight or ten inches wdien transferred. The central portion of 

 the head of the plants remains green, while the large leaves turn 

 slightly yellow ; then in the course of a week or ten days after 

 setting out, the most severely affected plants fall over, as if cut 

 off by worms, and on examination it is found that the lower part 

 of the stem is hollow, leaving only the epidermis to support the 

 plant. 



Plants affected with hollow stem make little or no growth. 

 Prof. Rolfs found that this trouble is caused by forcing the 

 ])lants in the seed-bed, and anything which induces a soft, watery 



1. Conn. Agr. Kx\). Sta., Ann. Uei)t., 1896, i). 232 



2. Fla. Agr. Exp. Sta., Bui. 47, 1898, p. 51. 



