HOW TO CONTROL THE PEAR THRIPS. 



23 



commercial tobacco extract No. 1, which is a (hirk, almost viscous 

 liquid containing 2.75 per cent nicotine, at the rate of 1 to 75; or 

 tobacco extract No. 2, which is a light-colored liquid containing 40 

 per cent of almost nonvolatile nicotine at the rate of 1 to 1,500, or a 

 fraction more than a pint to a 200- 

 gallon tank. This form of the nicotine 

 has been highly efficient and will in 

 all probability be more satisfactory 

 than the former. By reason of its 

 greater concentration the handling 

 and transportation charges will be 

 much less ; also, the nicotine contained 

 in this ])reparation is much less vola- 

 tile, thus allowing the use of a smaller 

 amount of actual nicotine in the dilu- 

 tion, as it remains an active killing 

 agent for a longer time on the trees. 

 In Santa Clara County greater 

 dilutions than these have been found 

 to be satisfactory, due most likely to 

 different climatic conditions, evapo- 

 ration there being much less at this 

 time than in the interior counties 

 where the atmosphere is drier. Grow- 

 ers in the Santa Clara Valley are 

 advised to use the 3 per cent distillate-oil emulsion, with tobacco 

 extract No. 1 added at the rate of 1 to 100 or tobacco extract No. 

 2 at the rate of 1 to 2,000. These recommendations hold for all 



thrips sprayings, for both adults and 

 larva3 and on all varieties of deciduous 

 fiaiits attacked by the pear thrips. No or- 

 chards should be sprayed, however, when 

 the trees are in full bloom. All spraying 

 for adults should be done before the blos- 

 soms appear and spraying for larva^ after 

 a large ])roportion of the ])etals have 

 fallen. 



In the prune orchards of Santa Clara 

 Valley deep fall plowing and cross-])low- 

 ing has proved a valuable and profita- 

 ble aitl in controlling tlie thri])s. Those who can do so are strongly 

 advised to irrigate their orchards in September or October, and when 

 the soil is in proper condition plow with disk plows to a depth of 7 or 



Fig. 14. — Buds of Black Tartarian cherry at 

 time of first application against thrips. 

 About one-half natural size. (Original.) 



Fig. 15.— Angle nozzle of the large cham- 

 ber type used in spraying experiments. 

 (Original.) 



