8 



BULLETIN 807, U. S. DEPARTMENT OF AGRICULTURE. 



The cost of hand picking to remove the weevily beans also de- 

 pends on the degree of infestation, but it is estimated at about $1.50 

 per 100 pounds. 



' Estimates of the reduction on the total horse bean acreage, because 

 of the increase in weevil infestation, range from 25 to T5 per cent. 

 Alameda County was formerly the largest producer, but at present, 

 due largely to the extensive infestation of all horse beans grown there, 

 practically no beans are produced commercially. It is also estimated 

 that if weevil infestation could be prevented, the acreage for the dry- 

 bean crop alone would be increased from 100 to 300 per cent in that 

 county. 



It will be seen from Table III that there is considerable varia- 

 tion in the percentage of infestation in the different districts. There 

 is also great variation in the number of weevils developing in a single 

 bean. In the case of the pea weevil B. pisorum (fig. 3) , with a very 

 similar appearance and life history, only one weevil develops in a 

 seed, but with the broad-bean weevil there are often two and three 

 adults in a single bean, while it is not at all rare to find four, five, and 

 even six. The following table illustrates this : 



Table IV. — Summary of the percentage of broad beans infested with different 



number of iveevils. 



Number beans examined. 



Locality 

 raised. 



Year 

 raiSed. 



Num- 

 ber 

 weevils 

 per 



bean. 



1 wee- 

 vil per 

 bean. 



2 wee- 

 vils per 

 bean. 



3 wee- 

 vils per 

 bean. 



4 and 5 



weevils 



per 



bean. 



Total 



per 



cent 



infested. 



1,000 



Hayward.... 

 do 



1915 

 1916 

 1917 

 1917 

 1917 



371 

 331 



781 

 880 

 573 



367 

 324 

 164 

 105 

 227 



186 

 216 

 46 

 14 

 140 



63 

 95 

 9 



1 

 29 



13 

 34 

 

 

 31 



62.9 



1,000 



66.9 



1 000 



.. .do 



21 9 



1,000... 



Stockton 



Hayward 



12 



1 000 



42.7 













58.9 



23.7 



12 



3.9 



1.5 



41.1 











LIFE HISTORY. 



The eggs are laid on the outside of the green pods, being cemented 

 to the latter by a glutinous secretion. They are laid singly and in- 

 discriminately over the surface of the pods (see PL I, fig. 1) without 

 apparent reference as to whether the position is favorable or un- 

 favorable to the newly hatched larva getting into the young bean. 

 The number of eggs on a pod also bears no relation to the number 

 of beans it contains, as often the former exceeds by many times the 

 number of larvse which might develop therein. One pod 4 inches 

 long was observed with 55 eggs deposited on it. The following table 

 shows the variation in number of eggs laid on a pod. 



