ANNUAL REPORT, 1938 41 



Considerable testing of diluents for impregnated pyrethrum dusts was also 

 done. So far, talc and gypsum, costs and performance both considered, seem 

 prefeiable to other materials for this purpose. 



As June and July were both very rainy on the Cape, many growers had difficulty 

 in finding good weather for treating their pests. In this extremity, some suc- 

 ceeded in controlling the black-headed firewoi m well by applying impre6,nated 

 pyrethrum dusts when the cranberry vnes were far from dry and even during 

 light raino. 



Prevalence of Cranberry Pests. The relative general abundance of cranberry 

 pests on Cape Cod in the season of 1938 was as follows: 



1. Black-headed fireworm {Rhopohota) on the whole considerably less pre- 

 valent than usual. 



2. Fruit worm {Mineola) much more abundant than in 1937 in Barnstable 

 County, but generally less prevalent than normal. 



3. Weevil (Anthonomiis) more prevalent than usual, especially on the outer 

 part of the Cape. About as in 1937 



4. Fire beetle {Cryplocephal us). See above. 



5. Gypsy moth not very troublesome in Plymouth County, much less so than 

 in 1937; e.vtremely destructive in much of Barnstable County, \-ery much more 

 so than in 1937. 



6. Blunt- nosed leafhopper (Ophiola) relatively scarce, probably largeK 

 because of general eflfective treatment. 



7. Green spanworm (Itame sidphwea) and brown spanworm (Ematurga) 

 seem to have become gradually more abundant during the last three years. 



8. Armyworm (Leucania unipuncta) more prevalent than usual. 



Control of Cranberry Bog Weeds. (Chester E. Cross.) About 600 different 

 weed plots ranging in size from 4J4 .\ 6 feet to an acre were treated with various 

 chemicals. Copper sulfate, cyanamid, Elgetol, ferric sulfate, ferrous sulfate, 

 kerosene, Sino.x, sodium arsenate, sodium arsenite, sodium bisulfate, sodium 

 chlorate, and sodium chloride were tried as weed killers in various ways. In 

 addition to this strictly experimental work, the results of the weed treatments 

 applied by numerous growers were inspected carefully, especially with regard 

 to the effects of spring and early summer applications. The growers, for example, 

 used over 50,000 gallons of kerosene this year and the results of their work gave a 

 clearer idea of the use and effectiveness of this oil. The main results of all this 

 work were: 



1. There should be no walking on or dragging of hose over cranberry vines 

 recently treated with any of the chemicals found useful in killing weeds. The 

 mechanical injury caused by such practices seems to provide entrance to the 

 interior of the cranberry foliage for the toxic materials. Those applying such 

 sprays should always back away from their work as it is done instead of advancing 

 into it. 



2. It was thought last year that a solution of sodium chloride, 75 pounds in 

 100 gallons of water, could be applied to cranberry vines in any stage of growth, 

 be it bud, blossom, or fruit, without causing appreciable injury. This year's 

 work, coupled with adverse weather conditions, proved this idea to be incorrect 

 and led to many tests of the concentrations and quantities of weed-control solu- 

 tions of copper sulfate, ferrous sulfate, sodium arsenate, sodium chloride, etc. 

 These tests seemed to show that the concentration of these solutions is not particu- 

 larly responsible for injury to cranberry vines and that the quantity applied is 

 much more important. 



3. Cranberry bogs should be rather thoroughly dried out before kerosene is 

 applied to control weeds. Water at the bog surface prevents the penetration of 



