THE BLACKHEAD FIREWORM OF CRANBERRY. 37 
Vines which are rather heavily infested will require the first year 
all three applications, as outlined above, and an additional fourth 
application, which should be made during the first two weeks of 
July. This last spray is designed to give protection, both to the 
berries and to the upright tips in which the fruit buds for the fol- 
lowing year's crop are forming, against late hatching larvae of the 
first generation and the first larvae of the second generation. It is 
also designed to kill many of the moths of the first generation, and 
it should, therefore, be timed so as to come within the limits men- 
tioned, as it is about this time that the moths are flying in largest 
numbers. By careful spraying with an outfit like that shown in fig- 
ure 13, one application at this time will clean a bog of fireworm moths 
and thus prevent a large number of the eggs of the second generation 
from being deposited. 
Kind of Equipment. 
A 50-gallon wheel-barrel outfit, with a strong pump, will usually 
be found sufficiently large for bogs up to several acres in extent. For 
larger bogs the power outfits of various sizes will be most economical, 
and in order to avoid dangerous delays at spraying time one should 
be sure that the parts are not only durable but easily accessible and 
replaceable as well. 
Any arrangement of nozzles and manner of spraying the bog that 
will insure thorough application of the spray as previously outlined 
and at the same time cause a minimum injury to the vines from walk- 
ing or dragging the hose over them will be satisfactory. 
After a consideration of the factors which influence the hatching 
and development of the blackhead fireworm (see pages 8-9), it would 
seem reasonable to suppose that a covering of water held over the 
vines until late in the spring, say until about April 10 to 15, together 
with the thinning out of thickly vined bogs, would have a very bene- 
ficial effect. It would also facilitate good control work by grouping 
the hatching of the larvae. In view of the fact that it is also con- 
sidered a good horticultural practice on the Pacific coast, this method 
of bog management in connection with spraying is to be recommended 
wherever it is practicable, especially on bogs which are badly in- 
fested with fireworms. 
SUMMARY AND CONCLUSIONS. 
The blackhead fireworm (Rhopobota naevana Hubner) is the most 
important pest of the cranberry on Pacific coast bogs. It is found 
also on native cranberry vines well isolated from cultivated bogs, 
but was doubtless introduced on these cultivated bogs on cuttings 
from eastern cranberry districts. So far as known on the Pacific 
coast, it feeds only on the cranberry. 
