388 Journal of Agricultural Research voi.x, No. s 



As heat is very penetrating, it occurred to the writer that possibly it 

 could be used against this mite, but it was found that the plants could not 

 be subjected to sufficient heat to kill the mites. 



Finally, the volatile liquid-nicotine extracts and the nonvolatile or 

 staple extracts, as "Black Leaf 40," may be used on cyclamen against 

 this pest. "Black Leaf 40" has been used in Connecticut with safety on 

 snapdragon plants, with the result that the new growth came out clean 

 and uninfested. Fir-tree oil was also used with some success on snap- 

 dragons. However, no experiments were carried on mth the use of " Black 

 Leaf 40" or the volatile nicotine extracts against the mites on cyclamen 

 plants. In the experiments carried on in several of the greenhouses in the 

 vicinity of Corvallis, Oreg., neither the volatile extracts nor the non- 

 volatile nicotine extracts, such as " Black Leaf 40," with the addition of a 

 small quantity of soap injured the young plants or the older plants when 

 used at the rate of i to i ,000, or a teaspoonf ul to a gallon of water. 



The staple nicotine extracts and the volatile nicotine extracts are prac- 

 tically identical, so far as killing properties are concerned. The non- 

 volatile extracts are, however, much cheaper, and wherever it is safe to 

 use this form should be employed with the addition of a small quantity 

 of soap. The soap assists in preventing the formation of small drops, 

 which tend to roll off without penetrating to and thoroughly wetting 

 the mites, causing the spray to cover surfaces more in the form of a thin 

 film, also giving better penetration and sticking properties. 



The volatile nicotine extracts, however, are preferred by most florists, 

 in that they may be used for fumigating purposes and are preferred for 

 those strains and varieties which might be injured by the use of the 

 staple nicotine extracts which contain sulphate. "Black Leaf 40" has 

 been used on chrysanthemums, snapdragons, and cyclamen plants with 

 safety at the rate of i to 1,000, with the addition of a small quantity of 

 soap, either 3 or 4 pounds to 100 gallons of the solution. 



The florist should not wait until his plants are fairly grown before 

 making an application of spray, but should start when the plants are 

 quite young. Cyclamen seeds are usually sown in flats in rows i yi inches 

 apart about the middle of August, with other sowings made until Jan- 

 uary, depending on when the flowering plants are desired. In about 8 

 or 10 weeks after they are sown, the plants will be ready to be transplanted 

 into other flats or into 2}4-va.ch pots, as the case may be. They will not be 

 more than i inch to i X inches high (PI. 5 1 , 5) ; this is the time when the 

 first spraying should be made. From then on the plants should be 

 sprayed with the "Black Leaf 40" or some of the volatile extracts at the 

 rate of a teaspoonful to a gallon of water, with the addition of a small 

 quantity of soap, every 10 days until the flower buds are well developed 

 and begin to show color. Do not spray after this, as the solution has a 

 tendency to discolor the flowers, and the plants are then far enough along 

 that the mite can do no damage. 



