36 MASS. EXPERIMENT STATION BULLETIN 369 



The dust containing 2 percent of rotenone and an activator and wetter was again 

 beautifully effective when used twice, at the proper times, at the rate of 100 

 pounds an acre. Derris dusts of one and a half and one percent rotenone content 

 with activators and wetters, used twice at 100 pounds an acre and well timed, 

 failed to give satisfactory control. Some of the cranberry growers used 50 pounds 

 to the acre of 4 percent rotenone derris dust without an activator and were well 

 pleased with their results. 



Alorco cryolite, 6 pounds in 100 gallons, 400 gallons an acre, and cryolite dust, 

 30 pounds an acre, were used in Carver on July 15 and again on July 25, times 

 when rotenone materials were effective. The fruit worm was controlled almost 

 completely without material injury to vines or fruit, though the first spray seemed 

 to dwarf the berries a little. Samples of the fruit, scooped from the treated areas 

 on September 9, were analyzed for fluorine residues by the Fertilizer and Feed 

 Control Division of the station at Amherst. The fluorine residue on berries 

 fiom the sprayed plot was .0023 grains per pound of fruit; from the dusted plot, 

 .000945 grains per pound of fruit. When these residues are compared with the 

 legal tolerance of .020 grains per pound of fruit set for fluorine, the danger in this 

 connection from using cryolite seems negligible. It should be noted, however, 

 that over 4 inches of rain fell in a single storm the last of August in the region 

 where these treatments were applied. The rainfall otherwise between the use 

 of the cryolite and the picking of the samples was light. 



On August 10, a bog in East Sandwich with a third of the berries already in- 

 fested with fruit worms was sprayed with 6 pounds of cryolite in 100 gallons of 

 water, 400 gallons an acre. The control obtained was excellent, the worms doing 

 very little further harm while they took all the fruit on untreated ajoining areas. 

 The berries were picked September 19 and had a fluorine residue of .00084 grains 

 per pound of fruit. 



It may be best to use rotenone materials, in spite of their higher cost, in the 

 first treatment for the fruit worm, because they are somewhat safer and because 

 they will at the same time check the blunt-nosed leafhopper, the spittle insect, 

 and the second brood of the black-headed fireworm. The second treatment 

 probably should be with cryolite dust because of the low cost for material and 

 application — only about $4.50 an acre. The dust leaves less residue than the 

 spray (see analyses above). It is less likely to harm the crop at the time of the 

 second treatment than it is when the first is applied. 



Black-headed Fireworm (Rhopobota). The second brood of this insect was 

 treated very successfully on a number of areas with about 50 pounds to the acre 

 of 4 percent rotenone derris dust without an activator. 



Blunt-nosed Leafhopper (Ophiola). On July 6, an area with a leafhopper 

 infestation of 310 to 50 sweeps of the net was dusted with a diluted derris dust 

 containing one and a half percent of rotenone, camphor oil as an activator, and 

 a wetter, 95 pounds to an acre. It was examined July 16 and then had only one 

 hopper to 50 sweeps of the net. 



On July 11, an area with 450 hoppers to 50 sweeps was dusted with a diluted 

 derris dust containing one percent of rotenone, peanut oil as activator, and a 

 wetter, 100 pounds to an acre. There was a considerable rain on this area for 

 15 minutes in the morning and another of the same duration in the afternoon 

 on July 12. Only 26 hoppers to 50 sweeps remained on July 16, the kill having 

 been 94 percent. Another area treated and examined on the same dates and in 

 the same way, except that 91 pounds of dust an acre and camphor oil as an acti- 

 vator were used, showed a kill of 94 percent. In relation to their efi'ectiveness, 

 these treatments seem to be as cheap as any that have been tried on this pest 

 so far, the cost of materials and application being about $10.00 an acre. Judging 



