TXSlsCI'IClDKS. 17 



to tlic prcseiU tiiuc. cnusod a iiiucli lar<>t'i' pcivciitagc of iiijiirv (o 

 tobacco grown iiiuier the slat shade. I)uriiii>- the suiiinier 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 thripsV work, can not be told at present, but the matter is im- 

 portant and should be watched closely. 



INSKCTICIDKS. 



In carrying on experiments to determine the most effective and 

 practical insecticides, reference was made to Professor Quaintance's 

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

 insecticides Avhich Professor Qiiaintance found to be most effective 

 on Euthrips tr'itici were given repeated trials. As a result it was 

 found that the resistance of the tobacco thrips to insecticides is far 

 greater than that of Eutlirips fntici 



In experimenting with insecticides three important points, asidi- 

 from their effect upon the insect, were to be 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 parts of thrips, Avhich are fitted for piercing and sucking, 

 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 

 has been found that the adult feeds largely on the ui)per surface of the 

 leaves. In this habit, thei-efore, lies our opportunity to treat the 

 ])est successfully with insecticides. 



Among the insecticides experimented with are the following, 

 the sprays being applied with a knapsack sjirayer: 



Rose-leaf wHecticide. — This is a high-grade extract of tobacco. 

 Professor Quaintance, in his experiments with the wheat thrii)s. 

 finds this insecticide to be the most effective and practical remedy 

 for use against the thrips affecting strawberries, and recommends 

 for that species 1 part to 48 of water. This strength, when used 

 upon the tobacco thrips. has but little effect. Various strengths 

 were tried. AVhen 1 part of the insecticide to 20 parts of water is 

 used, the thrips seem to be paraly/ed. remaining inunovable for 

 al)ont an hour and a half, after which they commence to show life, 

 and soon become as active as ever. Further experiments with this 

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

 the following j)r<)porlions : 



IvdS'.'-h'.Mf insecticide. 1 <iu;irt. 



Wliale-oil soap i liound. 



Water 20 quarts. 



"lUil. 4t;. Fl;i. Airi-ic. Kxp. St;i., .July. 1S<.H. 



