32 GRASSHOPPERS AND OTHER INJURIOUS INSECTS OF 1911 AND 1912. 



be avoided in this process and incidentally recording results of cer- 

 tain experiments of his in 1912: 



"Although I was not supposed to g-ive any attention to the economic phase 

 of the subject of grasshopper destruction, for my own information and that I 

 might be armed for the future, I took occasion to make a few investigations. 

 During the previous year you had been testing a modification of the South 

 African locust spray, adapting it to Minnesota conditions, and thought it to 

 be very effective. As one of the originators and perfectors of that spray, I 

 was anxious to see how it acted under local conditions. I took it upon myself 

 to find a farmer who had grasshoppers quite badly and watch his spraying 

 experiments with the sweetened arsenical spray. It will be as well in this brief 

 report to summarize results and give the gist of my opinion upon spraying. 

 The work carried out upon this farm was not very effective. It de)no)tstrated 

 all tJie ^iiistakes whicli could be made by a fainner in spi'aying. In the first 

 place, spraying was delayed until too late; hoppers were already molting to 

 the adult stage. In the second place the grain was too high, already heading 

 out, and there was plenty of tender pigeon grass below, of which the grass- 

 hoppers are very fond. In the third place, the spray machine used was not 

 suitable; the fans of spray were not wide enough to meet and it did not throw 

 the spray downward, so that relatively only a small portion of the grain was 

 covered with spray. In the fourth place, the field was sprayed in strips, 

 checker-board fashion, which leaves intermediate squares with no spray. My 

 opinion is that locusts are not attracted to the sprayed grass by the sense of 

 smell but when they come to a sprayed patch ai'e induced to stay there and 

 feed because of the sweetening in the spray. Therefore, unless we have a 

 species rapidly migrating, as is the case with the S. African locusts, the whole 

 field must be sprayed. 



Spraying to be successful mvist therefore be done early before the hoppers 

 have passed beyond the third stage, and if possible while they are in the first 

 or second stage. As most of our destructive grasshoppers oviposit along road- 

 ways and in abandoned land, these areas can be sprayed and no harm done 

 before the grain is more than six or eight inches high, while the hoppers are 

 still small and while it can be well covered with the spray. A suitable pump 

 should also be used, one which will give an even pressure, and with nozzles 

 which will throw fans of spray which will meet and insure the grain being 

 covered thoroughly. I would not advise the checker-board system of spraying 

 for the reasons given above. 



To test more thoroughly the question of whether grasshoppers and 

 locusts are attracted by any odor in the spray, I made a few cage experiments 

 with such odors as oil of rosemary, karo syrup, and fermented molasses and 

 syrup. My tests of these gave negative results, as none seemed more attract- 

 ive than untreated grass. I am strongly of the opinion, after very careful con- 

 sideration of the subject, that locusts are not attracted by odors, but by taste, 

 i. e., when they come upon something which suits their sense of taste, they 

 remain there and feed until satisfied or some other stronger factor causes 

 them to move away. In this connection, I also tried a test in the field with 

 several sweetening substances in the sj^ray. The following substances were 

 used: molasses, karo syrup, fermented molasses, beet sugar molasses and 

 locusticide. The sweetening substances, except of course the locusticide, were 

 combined in the usual formula for the spray as recommended by this office. 



The spray was applied at Foxhome on July 5th, on a weedy and grassy 

 roadside, along a field of grain where grasshoppers were veiy thick. The 

 lilots were 15 feet square and on July 9th the plots were examined and dead 

 grasshoppers were looked for as far as 30 feet into the grain field. The 

 following number of dead hoppers were found: 



Molasses 40 dead 



Karo syrup 192 " 



Fermented molasses 102 " 



Beet sugar molasses 409 " 



Locusticide 136 " 



