MONTANA EXPERIMENT STATION BULLETIN 384 



about one-seventh of that amount, or $940,924. In 1939 preparations 

 were made in advance for a strenuous campaign, and in spite of dif- 

 ficult complicating factors, the savings were estimated at $6,835,758, 

 and the losses considerably less than half of that amount, or $2,867,- 

 923. Again in 1940 there was warning of the possibility of a diffi- 

 cult situation in north-central Montana, and extensive preparations 

 were made to meet the condition. The savings amounted to an esti- 

 mated $7,012,763, and the losses were less than a third of that 

 amount, or $2,155,631 (table 2). 



In order to make preparations to meet such emergencies, the 

 annual grasshopper survey is the most valuable field tool at our dis- 

 posal. The accuracy of prediction, as to areas involved, has been 

 increasing from year to year. It has been obvious, however, that er- 

 rors have been large on the basis of predicting the amount of bait 

 which may be used in a county. There are so many variable factors 

 which affect the amount of bait which may be used (weather, inten- 

 sity of infestation, availability of outside assistance, cooperation of 

 involved agencies, ability of personnel, use of cultural methods, 

 natural control, time and evenness of hatch, flights, species in- 

 volved, survey adequacy, type of farming, etc.) that wide differ- 

 ences between bait prediction figures and bait usage figures are to 

 be expected. 



0-9.9 



10-19.9 20-293 30-39.9 40-49.9 50-59.9 60-69.9 10-19.9 80-89 9 

 AVERAGE PER-CENT INFESTATION BY 10 PER-CENT GROUPS 



Figure 2. Correlation between percentage of predicted bait used and the 

 intensity of infestation. Montana counties, 1937 to 1940. 



