ANNUAL REPORT, 1946-47 .39 



Other materials were discarded for reasons indicated: 



Amino azobenzene — effective, but left disastrous yellow residue. 



Isopropoxyl diphenyl amino — ineffective. 



Vultrol (U. S. Rubber Co.) — ineffective. 



Dichloraniline — effective but caused severe plant injury. 



CioHeCls (Velsicol) J^ ounce-1,000 - ineffective as used. 



Biology and Control of the Celery Plant Bug. (W. D. Whitcomb and Wni 

 Garland, Waltham.) The results of the insecticide experiments on the celery 

 plant bug in 1946 show that nearly all of the materials used killed the bugs well 

 and eliminated them from the plants immediately after treatment. From the 

 standpoint of lasting protection, however, the sprays of DDT wettable powder 

 were outstanding and no bugs were found on the count plants in these plots tor 

 the remainder of the season. 



From a practical standpoint, 1 pound of 5C percent DDT wettable powder in 

 100 gallons of spray (J^ pound actual DDT) was as effective as the 2 pound-100 

 gallon dosage. DDT-talc dusts containing 3 and 1 percent were effective for a 

 month and gave good protection from black heart; but l^ percent DDT dust 

 apparently requires applications at 10-15 day intervals to give adequate pro- 

 tection. Dry Pyrocide 73^ dust is also effective but requires more frequent 

 applications. Special Multicide {14, percent DDT and pyrethrum) was the most 

 effective dust used, with 97.94 percent of the plants free fronrblack heart injury, 

 and was very promising under the conditions of the experiment. Applications 

 of this dust at 30-day intervals should be satisfactory. Sabadilla-lime dust 10 

 percent gave protection for only a few days. 



Based on these experiments, practical control of the celery plant bug, Ly^its 

 campestris, and the resulting black heart injury should be obtained by spraying 

 about August 10 with J^ pound of DDT (1 pound 50 percent DDT wettable 

 powder) in 100 gallons of water or fungicide, and if necessary following with Dry 

 Pyrocide 7J^ dust about September 20 when the second generation of the plant 

 bugs is most abundant. 



The use of DDT on celery involves a residue tolerance which has been set, at 

 present, by the U. S. Food and Drug Administration at 7 parts per million. 

 Analyses to determine the relation of the effective treatments to the residue 

 tolerance will be made as soon as possible. 



Biology and Control of the Grape Cane Girdler. (W. D. Whitcomb and Wm. 

 Garland, Waltham.) On unsprayed grape canes, grape cane girdler beetles 

 lived an average of 114.2 days and made 18.8 scars per beetle. Sprays of DDT 

 wettable powder killed the beetles in 2.57 days and reduced the scars to 0.23 

 per beetle. There was no significant difference in effectiveness of }4, 1, 2, 3, or 4 

 pounds actual DDT per 100 gallons, and DDT was equally effective when com- 

 bined with basic copper sulfate or Fermate. Benzene hexachloride 50 percent 

 wettable powder containing 6 percent gamma isomer was also effective, at the 

 above dosages, when repeated after 5 days. Lead arsenate was slightly less 

 effective at dosages of 3 or 4 pounds per 100 gallons. The most effective treat- 

 ments were combinations of DDT, 1 pound actual, with 2 pounds of benzene 

 hexachloride as above, or with 2 pounds of lead arsenate per 100 gallons of water. 



In the vineyards, prevention of girdled canes and other injury was more de- 

 pendent on spraying whenever the canes increased their growth about 6 inches 

 than on the insecticide formula used. 



