20 BULLETIX 807, U. S. DEPARTMENT OF AGRICULTURE, 
It would seem, therefore, from consulting the tables giving the per- 
centages of infestation for seed planted in different months, from 
the insect's life history, and from the rate of growth and pod setting 
by the plant, that whenever possible it will be advisable to delay the 
planting until from the latter part of February or the first of March 
to May. A glance at Tables XIV and XVII will show that plantings 
prior to February and March show much higher percentages of 
infestation than those planted subsequently. 
This contention is further borne out in the experience of the 
Oceano-Morro district in San Luis Obispo County. It was the cus- 
tom there to begin planting about Xovember, continuing all winter 
and spring. For several years the horse beans had been seriously in- 
fested with the bean aphis {Aphis rumicis L.) which also did severe 
damage to the later planted crops of small white and pink beans. 
Assuming that the early planted horse beans acted as a winter host 
for the bean aphis, propagating it in great numbers before the more 
extensive plantings of other beans were made, the horticultural com- 
missioner persuaded all horse-bean growers to delay planting in the 
1917-18 season until March 1. This agreement was adhered to with 
a few minor exceptions, and the result is shown in Table III. The 
maximum and average percentages of infestation for the Oceano- 
Morro district for 1916 are 50 and 11.5 per cent and for 1917. 63 and 
11.5 per cent. In both these years a good share of the crop was from 
seed planted early, that is. from Xovember to March, but in 1918, 
when practically no seed was planted until after March 1, the maxi- 
mum and average per cent of weevil infestations are 17.2 and 2.92, 
a reduction of over 75 per cent. The majority of the plantings were 
not infested at all, particularly those which had been planted in 
April and May. 
The planting season begins soon after the first rains, or ordinarily 
in October and Xovember, in some sections, while in others it is de- 
layed until spring. The former are the drier inland sections where 
the crop must be matured before the warm dry weather of the early 
summer, and the latter are the low, cooler, coastal valleys where the 
summer heat is not high enough to affect the crop. 
The earlier plantings, especially in the dryer sections, usually pro- 
duce larger crops than late plantings. This is particularly true 
where the beans are raised without irrigation. The climate and soil 
conditions, therefore, as well as the availability of irrigation water, 
must be taken into consideration in arranging for a delayed planting 
program. TVhere late planting can not be practiced because of these 
conditions, it is especially important that all seed either be unin- 
fested or treated to kill the weevil before planting: but where con- 
ditions are favorable, planting should be delayed as late as is com- 
mensurate with getting a good crop. 
