THE BROAD-BEAN WEEVIL, 



19 



Table XV. — Comparing the degree of loectnl itifa^tiition in hor.se heann from 

 all di.slricis in California, planted in different months. 



Y(ydr. 



Oct. 



Nov. 



TX'c. 



Jan. 



Fob. 



Mar. 



Apr. 



May. 



1910 ■ 



Per cent. 

 46 



Per cent. 

 47 

 50 

 30.1 



Per cent. 

 15.2 

 15.6 

 19.1 



Per cent. 

 14.4 

 17.5 

 IS. 5 



Per cent. 

 5.2 

 8.21 

 ir>. 7 



Per cent. 

 9.6 

 12 

 12.9 



Per cent. 

 1 



Per cent. 

 



11)17 





1918. 





4.3 



g 















42.3 



10.6 



10.7 



9.7 



11.5 



2.6 



.4 











To test tliis out further, plantings of horse beans were made at 

 Pasadena, xilhambra, and Ilayward, for the years 1917 and 1918, 

 in which a certain number of beans were planted each month, and 

 when harvested carefully examined to find out the percentage of 

 infestation. The results are mven in Tables XVI and XVII. 



Table XVI. — Shoicing the percentage of iveevil infestation of beans planted 

 durv>ig certain months at Pasadena and Alhamhra. 



Year. 



Nov. 



Dec. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



19171 





17 



45 



11.5 

 15.5 



12 



8 



7.5 

 .75 



5 



2.6 



1918 



43.5 











1 Degree of infestation for 1917 crop found by counting larval entrance holes, which, are about 50 per cent 

 greater than number of adult weevils. ' 



Table XVII. — Shotving the percentage of infestation of beans planted during 

 certain months at Hayioard, Calif. 



Year. 



Nov. 



Dec. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



1917 









24 

 14 



18 



5 



9.6 



9.3 



1918 



74.5 



67.5 



32 











These tables clearly show that the later in the season the seed is 

 planted the lower the percentage of infestation will be. A possible 

 explanation of this may be found by referring to the seasonal history 

 of the insect, which shows that egg laying begins about the middle 

 of March, is heaviest in April, and extends to the middle of M.Sij. 

 Figure 5 shows also that at Hayward the first adults were observed 

 in a broad-bean field on March 18 and that the number constantly in- 

 creased each week to Ma}' 4, after which the number decreased as 

 constantly until June 15, the last date any were observed. Since the 

 eggs are laid only on the pods, it follows that any plants which pro- 

 duced pods prior to or during April will be subject to the greatest 

 egg deposition, and pods produced subsequently to the latter part of 

 April would be liable to little or no egg deposition. 



Seed planted from October to February begins setting pods in 

 March and April, while seed planted from the latter part of February 

 to May will begin setting pods from the latter part of April to June. 



