24 HOW TO CONTROL THE PEAR THRIPS. 



8 inches and harrow, then cross plow 8 to 9 inches deep and liarrow 

 again. All ])lowing should be done during the months of October and 

 November. During this season the thrips are passing through the 

 tender pupal stage and are more easily killed by mechanical means 

 than at any other season of the year. 



Plowing has not proved satisfactory' as even a partial means of 

 controlling the thrips in the pear orchards of the interior counties. 

 This is due, perhaps, to several conditions, one of which is the differ- 

 ent type of soil, and another, the fnct that tlie area of soil infested 

 with thrips around pear trees is very- much less than around prune 

 trees, the branches of which spread farther, covering a greater surface 

 of ground. The larva^ in leaving the trees fall to the ground directly 

 from the foliage and young fruit, rather than crawl down the trunks 

 of the trees; hence in a prune orchard they are more widely distrib- 

 uted throughout tlie soil between the trees and can be reached by the 

 })lows, while in a pear orchard most of the larvje in the ground are 

 close around the base of the trees. 



SUMMARY. 



The j)ear thrips can be controlled b}^ thorough spraying on any 

 A^ariety of the deciduous fruits grown in the infested areas of Cali- 

 fornia. 



The sprayings necessary to control the thrips are expensive, but the 

 outlay of money and labor gives large returns. Many experiments 

 in spraying have given net returns of from $100 to $600 per acre more 

 than was secured from adjoining untreated areas. 



The thrij)s work rapidly and may destroy all pros])ects of a crop 

 in less than a week's time. Spraying, to be successful, must be done 

 thoroughly and at the time to kill the thrips before the fruit buds 

 have been destroyed. 



Those who can do so successfully are advised to irrigate and plow 

 in the fall. This is to be followed by thorough spraying the follow- 

 ing spring. 



When the thrips begin to appear on the trees in numbers, spraying 

 should be done thoroughly, using high pressure, holding nozzles close 

 to buds, and directing the spray directly into the ends of the huds, and 

 not against the sides. 



Growers should not attempt to spray too many trees with one 

 machine. More profitable returns will be gained by sj)raying half of 

 the orchard thoroughly and at the proper times than by spraying all the 

 orchard poorly one time. Results of the work in 1909 and 1910 show 

 conclusively that one application is not sufficient when the thrips are 

 abundant. 



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