TIME OF Vl.vi; FOB FUMIGATION. 49 
of the insects of the large and more regular brood are batched and 
in their least resistant stage during September and October. In 
some favorable seasons the eggs are almost all batched in August. 
Moderately light fumigation dosage may be used against the black 
scale during this period with success. 
The black scale occurs in practically every citrus-growing locality 
of southern California, while the purple, red, and yellow scales, the 
other principal citrus pests, are more localized. A heavier dosage 
is u>cd for the latter insects than for the black scale. Where the 
other species occur in orchards infested with the black scale, it is 
a common practice to fumigate during the regular black-scale 
period, using the heavier dosage. The majority of these scale insects 
can thus l>e caught at one time. When fumigating for the purple 
scale alone, operations may be commenced as early in the season as 
tin 4 trees are in a condition to withstand the heavy dosage without 
injury, although probably it would be preferable to fumigate a little 
later in the fall. The purple scale is to he found in the egg stage 
throughout the year. There is a period in the fall and one in the 
early spring, however, during which the smallest proportion of eggs 
is to 1)0 found. With dosages lower than those of eradication, the 
best work can be accomplished at these times. 
The rod and yellow scales are viviparous and can be successfully 
destroyed throughout the year. 
In fumigating for any of the scale-insects there is one point 
worthy of consideration. Aside from trying to save the tree from 
destruction or from having its vitality impaired by the attack of 
scale pests, the orchardist fumigates principally in order to have 
his fruit come into the packing house as clean as possible. It would 
be well, therefore, to fumigate as nearly as possible to the time 
which would insure him the cleanest fruit. Although lemons are 
gathered throughout the entire year, the bulk of the orange crop is 
taken during the first six months. Thus fumigation during the fall 
and early winter would be sure to place the cleanest fruit in the 
packing house. If carried on in the late spring or early summer, 
such insects as remain undestroyed would have the opportunity to 
breed through a period of several months and infest much fruit. 
FUMIGATION DURING TIM: BLOSSOMING PERIOD. 
The statements by experts on fumigation as to tin 4 amount of 
injury resulting from work while the trees are in blossom are very 
conflicting. Some fumigators hold that a very light dosage will 
destroy the tender blossoms, while others believe that the blossoms 
will stand a heavy dosage. In order to decide this point much experi- 
mentation was carried on and many observations made throughout 
77488— Bui. 7«i— <»!» 1 
