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SOUBCE OF COBN BOSSES IK DAHLIAS 
The seasonal history of the European corn borer, previous to 
and Including the appearance of the second generation In dahlias, 
is illustrated in figure 1. It is important for the dahlia grower 
to note in this diagram that there are two generations of the 
European corn borer each year and that the larrae of the first gen- 
eration usually live in early sweet corn and field corn during June 
and July. These corn-inhabiting larrae change to moths in July and 
August, and some of the moths fly into dahlia gardens and deposit 
egg masses upon the under surfaces of dahlia leaves. Egg laying on 
dahlias may continue for a period of k to 6 weeks during late July, 
all of August, and early September. These egg masses (see figures 1 
and 2) are about one-eighth of an inch across and usually consist of 
from 10 to 25 flattened, overlapping, whitish, disklike eggs. The 
eggs hatch within a week and the young caterpillars disperse over 
the dahlia plant. 
HOV COBB SOBERS GET INTO DAHLIA PLANTS 
When one of these tiny caterpillars (less than l/l6 inch in 
length) crawls into a space between closely oppressed foliage at 
leaf and flower buds, or into an axial shoot between a branch and 
the stalk, it begins to feed upon the soft tissues of the unexposed 
parts. Sheltered in these spaces, it continues to excavate, driving 
deeper into the bud or into the pith of the branch or stalk until 
eventually it occupies a tunnel large enough to accommodate a full- 
fed larva that is about 1 inch in length. The type of injury caused 
by the corn borer in dahlias is determined by the kind of bud in 
which the young larva becomes established. Establishment of young 
larvae in terminal and lateral buds, as described above, results 
later in destruction of foliage and flower buds and in breakage of 
branches and the stalk. 
CONTROL 0? THE COBN BOBEB WITH INSECTICIDES 
Several facts of importance in control measures should be noted 
in connection with the manner in which the corn borer infests dahlias: 
(l) Entrance is made at points of new growth by very small, newly 
hatched larvae. (2) This initial infestation usually takes place 
during late July or in August (depending upon latitude and season). 
(3) Conspicuous damage, such as breakage in branches, does not occur 
until the caterpillar has reached a large size and is inside the 
plant, (k) Unless dahlias are carefully examined for signs of infes- 
tation or injury, such as 9gg masses or wilted leaves, black fraas, 
or castings, and stunted flower buds, the infestation may not be dis- 
covered until it is too late to protect the plants from further damage. 
Dahlias can be protected from serious corn borer injury if cer- 
tain insecticidal sprays or dusts are applied with suitable equipment 
at the right time. This method is effective when the spray or dust 
is directed at terminal and Lateral shoots while the young larvae are 
feeding upon accessible surfaces in the buds of these shoots. 
