32 MASS. EXPERIMENT STATION BULLETIN 327 



fruit worm eggs in laboratory tests. Only the dark form, however, parasitizes 

 this pest in nature and it might prove more useful. Fruit worm eggs infested 

 with this form were sent to Dr. Morrill and he is breeding it for field tests 

 next year. 



Blackheaded Fireworm (Rhopobota). A very unusual outbreak of the second 

 brood occurred on numerous bogs scattered throughout the cranberry growing 

 region, many that had not been attacked by this pest for a long period of years 

 being seriously affected. This may have been due to the abnormally cool 

 period in which the first brood developed, this weather probably having been 

 unfavorable to the development of the tungus (Entomophthora) which largely 

 controls this fireworm. 



Apple Sphinx (Sphinx gordius Cram.). This insect broke out on an area of 

 fifteen acres in such numbers that it threatened to destroy the whole crop. 

 Treatment with the usual stomach poisons seemed undesirable as the berries 

 were partly grown, the winter water having been drawn off early. The bog was 

 treated on August 12 with a dust mixture of one part of Derris (4 percent 

 rotenone) and 4 parts of clay, 100 pounds to the acre. The worms stopped 

 feeding at once and all died within five days. The largest worms were full 

 grown. 



Control of Cranberry Bog Weeds. (Wm. H. Sawyer and H. J. Franklin.) 

 Because of the urgency of service in weed control, Dr. Wm. H. Sawyer was 

 employed temporarily on funds provided by the Cape Cod Cranberry Growers' 

 Association to carry on work in this field. It is hoped that this service may be 

 extended. 



Hand Weeders. Some new types of these tools were developed and are likely 

 to be useful under some bog conditions. 



Chemical Weed Killers. Experiments were conducted with fuel oil, kerosene, 

 gasoline, sodium arsenate, sodium chloride, and iron sulfate, with the following 

 results most important: 



1. The light oil, gasoline, goes into the interior of leaves readily and so is 

 very harmful to cranberry vines as well as weeds. 



2. The heavier oil, fuel oil, evaporates so slowly that it is also very harmful 

 to cranberry vines and weeds alike. 



3. Kerosene, intermediate between gasoline and fuel oil in viscosity and 

 volatility, doesn't get into the leaf interior much and evaporates rapidly enough 

 to be only slightly harmful to the smooth cranberry foliage. 



4. Kerosene sprayed on grasses, rushes, and sedges collects inside their 

 sheaths and remains there many days after it. is applied. 



5. Because of all this, water-white kerosene, used at the rate of 100 to 400 

 gallons an acre, according to the grass, rush, or sedge concerned, is a good con- 

 trol for many of these weeds and probably can be used to real advantage to 

 clear many bogs of them. The following weeds of this sort were killed largely 

 or entirely by experimental applications of the kerosene: 



J uncus rushes Carex trichocarpa Muhl. 



Bunch grass (Scirpus) Carex scirpoides Schkuhr. 



Dulichium arundinaceum (L. ) Beak rush (Rynchospora) 

 Cyperus sp. Panicum virgatum L. 



Panicum mattamuskeelense Ashe 



6. Young seedlings of beggar-ticks (Bidens), one to two inches tall, are killed 

 readily with dry iron sulfate, 1 ' 4 ' tons to the acre. 



