58 MASS. EXPERIMENT STATION BULLETIN 150. 



worm by preventing the escape of the vesicle of air whicli it contains, 

 which the worm needs more than anjiihing else in order to sur^'ive, rather 

 than by keeping out the water by any imperviousness of its texture. 



Study of Control for Dry Bogs. 



The sanding experiment conducted last year to determine whether this 

 insect could be smothered in its cocoon was repeated and continued tliis 

 year on the same heavily infested bog, but the general results were unsat- 

 isfactory. It now seems pretty certain that this method of treatment for 

 this insect will never be practicable. 



In last year's report suggestions were made concerning the possibility 

 of starving out fruit-worm infestations on dry bogs by kilhng the remnant 

 of the bloom, in seasons of severe winter-kill injury or of severe frost 

 damage, by spraying with a 20 per cent, solution of iron sulphate. First 

 tests of the practicabiUty of this method of treatment were made this 

 year, and it was found that this solution can be used in such a way as to 

 kill the bloom without apparent injury either to the vines or to the buds 

 forming for the succeeding year's growth. It was necessary, however, to 

 apply three rather thorough sprayings to accomplish the entire destruc- 

 tion of the blossom, because of the fact that the blossoming does not all 

 take place at one time but is extended through a period of tlu'ee or four 

 weeks. The necessity of three sprayings instead of one has brought in a 

 new element of danger which must be considered in connection with the 

 practicability of this treatment. In making the 20 per cent, solution of 

 iron sulphate 100 pounds of the chemical are used to every 50 gallons of 

 water. It takes not less than 150 gallons to spray an acre thorouglily. 

 This means that with each application 300 pounds of the iron sulphate 

 would be put on each acre. Three applications would therefore deposit 

 nearl_y half a ton of this chemical, per acre, on the bog. It seems probable 

 that this amount of iron sulphate might injure the cranberr}^ root system 

 and perhaps kill the vines. Further experiments to determine about this 

 are planned. If there proves to be no danger in this way, it seeriis prob- 

 able that this method of treatment may be used to advantage on dr}^ bogs. 



8. WEEDS. 



Horse-tail {Equisetum spp.) is one of the most troublesome weeds "oith 

 which the cranberry grower has to contend. In general the growers show 

 more concern over this weed than they do about any other. For this 

 reason some attention was given to experimenting with it during the j^ear. 

 Solutions of copper sulphate as strong as 1 pound to 25 gallons of water 

 were injected into a bog where this weed was growing in abundance to 

 depths ranging from 6 inches to 2 feet, the solution being poured into holes 

 a foot apart each waj^ made with a crow bar, a quart of the solution being 

 used in each hole. Unfortunately, this treatment did not seem to affect 

 the horse-tail injuriously, but rather seemed to cause it to thrive instead. 



