SPRING NUMBER ie 
were dipped in a soap and nicotine solution or in a “Derris oil” 
solution and all aphids killed, and the other half left for a check. 
These twigs were carefully selected in pairs of practically the 
same degree of infestation, of similar size and vigor, and carry- 
ing about the same number of blossoms and buds. One member 
of each pair was dipped and the other not dipped. On the dipped 
twigs an average of 74% of the blossoms set fruit, and on the 
undipped 62. This difference, considering the small number of 
twigs, was almost within the limits of probable error. After 
the petals drop most of the aphids attack the calyx rather than 
the young orange, altho in this case enough attacked the young 
fruit to severely roughen it. Experience of last year indicates 
that as these oranges mature they will largely outgrow the 
bumps. 
The aphids do the most damage when they attack the very 
young sprouting buds, the “buttons” or “points,” as they burst 
thru the bark. One or two aphids can completely stop the 
growth of a “button” an eight or a sixteenth of an inch long. 
These embryonic twigs are often covered with aphids. For this 
reason control measures should be instituted upon the first 
appearance of these minute “points” of growth in considerable 
numbers. Spraying, moreover, is much more effective at this 
stage of growth than it is later on when there are curled leaves 
in which the aphids can find protection. Furthermore, in the 
early stages of the “flush” of growth when the amount of suit- 
able food is on the increase, comparatively few of the aphids 
develop wings. Hence, if one cleans up his trees at this time 
they will not be as quickly reinfested. In many cases it has been 
ten days or two weeks before the infestation again became heavy 
enough to cause much damage. It is. the maturing of the foliage 
that acts as a stimulus for the development of winged aphids. 
Moreover, this maturing of growth causes the wingless adults 
and young to become restless and move about. The dipping 
experiments on the blossoms mentioned above brought this for- 
cibly to our attention. The aphids on the twigs were counted 
and a recount a day or two later showed that sometimes as high 
as 50% of the aphids had disappeared, while many well grown 
individuals were found on the twigs which had been dipped but 
a day or two before. 
(2) Whatever measures are taken against the aphids should 
be thoro. Under favorable weather conditions an aphid will bring 
forth six young a day. This means that if the grower kills five- 
