22 MASS. EXPERIMENT STATION BULLETIN 293 



tained a brief statement of the results of tests to control certain cranberry pests 

 with pyrethruni dust mixed with a gypsum diluent of 300-mesh fineness. Al! that 

 dusting was done with hand dusters. 



This year work with this dust was continued, but with a Root power duster 

 mounted on a carriage home-made for use on cranberry bogs. In general the 

 results of this work were highly satisfactory. The rig was drawn around on the 

 bogs by two men, and they evidently injured the vines no more than spraying 

 operations do. 



Many tests were conducted in which different quantities of a mixture of the 

 dust, made up of 1 part of pyrethrum and 9 parts of gypsum by weight, were 

 applied in treating the false blossom leafhopper {Ophiola striatida). As little as 70 

 pounds to an acre gave a satisfactory kill in some cases; but because of the varia- 

 tion of pyrethrum in toxicity and of the difficulty of making an entirely even dis- 

 tribution of the dust, it was finally found that 100 pounds was about the right 

 amount to use. Reasonably careful dusting with this amount of the mixture was 

 commonly found to kill 99 per cent of the hoppers present. This treatment was a 

 more effective and generally more satisfactory control for this insect than either 

 spraying or flooding have ever been. It was also cheaper than spraying. Perhaps 

 its most important advantage over flooding and spraying is that it may be applied 

 without any risk when the vines are in full bloom and all the hoppers have hatched. 



A dust mixture of 4 parts of pyrethrum and 6 parts of gypsum, by weight, used 

 at the rate of 100 pounds to the acre, proved as effective as a pyrethrum soap spray 

 for the control of the second brood of the black-headed fireworm {Rhopobota 

 vacciniana) when the worms were small but rather well sewed up in the cranberry 

 tips. This dust has not been tried against the first brood of this insect. 



One part of pyrethrum to nine parts of gypsum, applied with hand dusters, 

 was fairly effective in killing the moths of the cranberry girdler (Crambus hort- 

 tielhis), but it is probable that a 2 to 8 mixture is advisable for this purpose. 



Gypsy moth and contact sprays. The gypsy moth was very abundant this year 

 in a large part cf the Cape Cod region. As this prevalence came after several 

 years of relative scarcity, it caught a good many of the cranberry growers napping, 

 and bog infestations were rather generally neglected till the worms were consid- 

 erably grown. This promised to develop into a serious situation, for stomach 

 poisons are not effective on cranberry bogs against the caterpillars of this insect 

 after their early stages, and very many bogs were without water supplies for 

 flooding. Immediate attention was given to work with contact sprays, and it was 

 found that the following sprays killed the worms in all stages satisfactorily when 

 used at the rate of 400 gallons to the acre: 



1. Pyrethrum soap 7 pounds 2. Nicotine sulfate I5 quarts 



Water 100 gallons Soap 4 pounds 



Water 100 gallons 



These sprays were most effective when applied early in the morning, for then 

 the worms usually work in the tops of the vines where they are easily reached with 

 a spray more than they do later in the day. 



Nicotine sulfate and the cranberry fruit worm, ll has become evident, as a result 

 of spraying carried on in several seasons, that a nicotine sulfate spray at the end 

 of the cranberry blossoming period controls the fruit worm to a considerable ex- 

 tent. As it has not been clear how it does this, special experiments were con- 

 ducted, and it was found that the insect is affected by the spray in the three fol- 

 lowing ways: 



