N$E< TICIDES. 1 



to the present time, caused a much larger percentage of injury to 

 tobacco grown under the slat shade. During the summer of 1905, 



however, they were found causing no small amount of injury to 

 tobacco under cheese cloth. Whether or not the meteorological dif- 

 ferences between cheese-cloth and slat shade have an influence on 

 the thrips's work, can not be told at present, hut the matter i- im- 

 portant and should he watched closely. 



INSECTICIDES. 



In carrying on experiments to determine the most effective and 

 practical insecticides, reference was made to Professor Quaintai 



bulletin entitled "The Strawberry and the Onion Thrips." The 

 insecticides which Professor Quaintance found to be most effective 

 on Euthrlps tritici were given repeated trial-. A- a result it was 

 found that the resistance of the tobacco thrips to insecticides i- far 

 greater than that of Eutkrips tritici. 



In experimenting with insecticides three important point-. aside 

 from their effect upon the insect, were to lie considered: First, their 

 relative cost: second, the expense involved in their application: and. 

 third, their effect, if any. upon the foliage. From the nature of the 

 mouth part- of thrips, which are fitted for piercing and -ticking. 

 stomach poisons were not available and contact insecticides were 

 necessarily used. These latter, as is generally known, kill by entering 

 through the breathing pores and setting up an irritation, or by closing 

 them and bringing about the death of the insect from suffocation. It 

 ha- been found that the adult feed- largely on the upper surface of the 

 leave-. In this habit, therefore, lie- our opportunity to treat the 

 pest successfully with insecticide-. 



Among the insecticides experimented with are the following. 

 tin- sprays being applied with a knapsack sprayer: 



Rosi -leaf insecticide. — This is a high-grade extract of tobacco. 

 Piof.— or Quaintance. in his experiment- with the wheat thrips, 

 find- this insecticide t<> be the most effective and practical remedy 

 for use against the thrips affecting strawberries, and recommends 

 for that species 1 part to 4s of water. This strength, when used 

 upon the tobacco thrips, ha- but little effect. Various strengths 

 w«-re tried. When 1 pan of the insecticide to -jo part- of water i- 

 used, the thrips seem to Ik- paralyzed, remaining immovable (or 

 about an hour and a half, after which they commence to show life. 

 and soon become a- active a- ever. Further experiments with this 

 insecticide -how it to be effective when used with whale-oil soap in 

 the following proportion- : 



i: se-leaf insecticide ._ i quart. 



Whale-oil soap | pound. 



Water _ 20 quarts. 



• Bui. -4i;. Fla. Agric. Exp. st.-i.. July, 1893 



