CARNATION WILT DISEASES 41 



ber to March. The differences in the yield of Number 1 carnations from October 



1930 to April 1931 inclusive are as follows: 



Water Naphthalene Percent 



Benching Date Syringing Fumigation Increase 



May 1_ 99 311 214.1 



July 1... _._. 215 568 164.1 



July 15 243 396 62.9 



August 15 - ... 145 159 9.6 



More blight developed on the plants as the season advanced which, as might 

 be expected, led to narrower differences in the yields of flowers between the two 

 methods of red spider mite control. 



The experiment was repeated in 1933-34. Matchless plants grown from Decem- 

 ber cuttings were planted June 9, 1933, in benches in each of two greenhouse com- 

 partments. The soil of one bench in each house was treated with hot water, 

 the soil of another with 1-50 formaldehyde solution, and the soil of the third 

 was left untreated. Naphthalene fumigation was practiced in one greenhouse 

 compartment throughout the period of the test. In the other the plants were 

 syringed with cold water. Satisfactory control of the red spider mite was not 

 obtained with water, and in December 1933 the compartment was fumigated 

 with naphthalene. The fumigation was repeated as necessary. The contrasts 

 in yields of Number 1 carnations per square foot from October to March, 1934, 

 inclusive, under the two sets of conditions are as follows: 



Naphthalene Percent 



Soil Treatment Water Syringing Fumigation Increase 



Hot Water 8.1 10.2 43.6 



Formaldehyde..... 8.6 11.0 27.9 



No Treatment 5.6 7.5 33.9 



Reviewing the results of the several experiments, the adverse effect of wetting 

 the plants with water in the presence of Alternaria blight is shown in the yield 

 of flowers. In the light of our knowledge of the influence of water on the de- 

 velopment of other parasitic organisms attacking the foliage, a similar contrast 

 might be shown in the presence of rust, bacterial spot, or fairy ring spot infection. 



The warm temperatures required for naphthalene fumigation cause an accelera- 

 tion of plant growth and also hasten the wilting symptoms of plants infected with 

 Fusarium or Rhizoctonia. W'hen wilting from such infections is present, more 

 of it can follow under warm greenhouse temperature conditions. 



Colonies of both Alternaria and Fusarium in nutrient agar culture plates were 

 exposed in a house of carnations warmed for fumigation with naphthalene for 

 6 hours on each of 4 successive days in January. Both sets of culture plates 

 were maintained for 4 more days in the greenhouse under conditions considered 

 more nearly normal for carnations. 



Average Diameter of Colonies Expressed in Millimeters 



FUNGUS CHECK N.A.PHTH.A.LENE 



4 Days 8 Days 4 Days 8 Days 



Fusarium cidmorum.... i.i 38 10 50 



Fusarium dianthi.... 1.6 28 7 40 



Alternaria dianthi 8.0 20 7.3 23 



In another test over a period of 3 days in February with 6 hours of fumigation 

 on each day, during which temperatures of 75°-80° F. prevailed in contrast to 

 temperatures of 50°-55° in an adjoining greenhouse section, the difference in 

 the average diameter in millimeters of the colonies on agar plates was as follows 

 at the end of 3 days: 



