522 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



it can with annual truck crops in which the entire business transaction 

 is completed within the one year. In the case of truck crops, the cost 

 of spraying may be charged to operating expense, whereas it is rea- 

 sonable to allow at least some of the expense of fruit tree spraying to 

 be charged to increased capitalization, being in much the same cate- 

 gory as the extension of railroad lines — a charge which is not proper 

 to consider under operating expense. 



In the control of pests that attack a wide range of food plants, the 

 usual statement made is that, in the particular field concerned, the 

 results would be only temporary and that in several days the field 

 would again be infested because of the migration of the insects from 

 nearby weeds and cultivated plants. This, in itself, has been con- 

 sidered a prohibitive factor; but under our own observations this is 

 not necessarily true. 



As typical of such problems may be mentioned Jassid attacks on 

 beans in the state of Florida. It is quite true that, upon spraying a 

 field, it becomes infested again later on. However, growers have 

 found spraying advisable, the purpose being to keep down a sufficient 

 proportion of the epidemic to permit the plants to become hardier 

 and reach that stage of development that will enable them to with- 

 stand a heavy attack of these pests, which, early in the season in un- 

 treated fields, have destroyed young, tender plants outright. 



An attack of insects on truck crops threatens the definite destruc- 

 tion of part or all of that particular season's business We have seen 

 hundreds of acres of cantaloupes totally destroyed by aphis, and large 

 plantings of onions rendered unmarketable by thrips. Destructive 

 epidemics of this kind emphasize the necessity of rearranging our 

 ideas concerning the factors that render the cost of spraying prohibi- 

 tive. 



What then should be the true economic attitude on this subject? 

 To formulate a rule covering this problem is, indeed, a difficult matter. 

 The writer, therefore, submits the following suggestion in order that 

 discussion may ensue, as a result of which a definite rule maybe devel- 

 oped which will apply eventually not only to truck crop spraying, but 

 to the spraying of fruit trees as well: 



Rule: The cost of spraying truck crops for pests that threaten to destroy 

 all or a large part of the crop does not become prohibitive until the imme- 

 diate application in view, together with such following farm operations 

 as can be definitely J oreseen, have a total cost in excess of the reasonable 

 expectation of gross returns from the crop in question. 



It is true that there will be many cases of applications, the necessity 

 for which cannot be definitely foreseen, with the result that at the end 

 of the season it will have been ascertained that the cost of spraying 



