6 MASS. EXPERIMENT STATION BULLETIN 239 



Black-Headed Fireworm.^ 



If we consider all the cranberry growing sections of the country, this is the 

 most harmful cranberry insect, and in Massachusetts the fruit worm alone has 

 done more damage. Means of control, however, Jiave now devehiped so that 

 much injury by it suggests poor management. 



On Cape Cod, this insect never harms seriously a bog that has not been 

 flooded during the winter, and its infestations cling more tenaciously to large 

 compact bogs than to small areas. The water kills or drives ashore its enemies, 

 such as s]iiders and parasites, and protects its eggs from winter adversities. 

 The foes of the pest are, of course, slower in again reaching the center of a 

 large compact bog in effective numbers than they are in reaching that of a 

 small one. So an infestation developing on a large bog always gets serious 

 on the middle jjart first. 



]>h-iril)utiou (Hid Food Phaits. 



This fireworm is very destructive in Massachusetts, New Jersey, and Wis- 

 consin and on Lt)ng Island and the coast of Oregon and Washington.*' It has 

 been fomid in Maine, California and Canada. It is not known to feed on 

 anything but cranberry.' It generally attacks Howes vines more than Early 

 Black. 



Chanicffr of Iiijuri/. 



The newly hatched worm of the first brood usually begins by burrowing into 

 the imder side of an old leaf, the new growth of the season not yet having put 

 out at all, and works as a leaf miner, casting out on the lower surface a small 

 mass of refuse (fig. 1). An area on the upper side immediately over these 

 castings is much lighter colored than the rest of the leaf, and the first hatch- 

 ing of the insect often may be detected most easily by these light patches. 



If the hatciiing begins early, tiie yoiuig worms, on leaving their mines in 

 the old leaves, mine the terminal buds just as they are swelling to start new 

 growth, and sometimes ruin most of them before being discovered. 



As new shoots appear, the worms proceed to sew three or four of their tip 

 leaves together. If the worms hatch after the new growth develops, they 

 usually go directly to the new tips without mining the old leaves. The webbed 

 tips generally are the first work noticed by growers (fig. 2). 



The worm usually leaves the tip it has sewed up within a few days and 

 either webs leaves farther down on the shoot or goes to another upright the 

 new growth of which it sews up, commonly webbing in one or more other up- 

 rights. If the worms are very abundant, two or three often work together 

 and include several iiprights in their nest (fig. -i). They feed freely on the 

 new leaves and flower buds in their nests, often destroying the whole crop 

 prosj)ect and turning the bog brown. 



During the interval between the two broods the vines put forth more new 

 growth and recover considerably from their injury. 



5. Rhopobola vaciiniana (Pack.). The writer is not convinced that this species is the same 

 as the European holly feeder, R. naevana (Hubner), and hesitates to follow Heinrich in this (cf. 

 U. S. Dept. Agr. Bill. 1032, p. 45, 1922). Dr. J. McDunnough seriously questions Heinrich's 

 conclusion. 



6. Only on tlie Pacific coast does this fireworm thrive generally on bogs not flooded during 

 winter. 



7. Vaccinium macrocarpon Ait. and T'. Oxycoccus L. 



