44 



2. Rate: Two lbs. per iooo cu. ft. of space. Time of ex- 

 posure, i hr., 15 min. ; sun shining. Plant treated: Tomato. Re- 

 sults: Adults began to drop from leaves in about 15 minutes; ap- 

 parently dead when box was opened, but all recovered in the course 

 of three hours ; plant uninjured. 



3. Rate: Two lbs. per 1000 cu. ft. of space. Time of ex- 

 posure, 6 p. m. to 8 a. m. Plant treated : Tomato. Results : 

 Adults apparently killed, but about 25 per cent recovered in the 

 course of two days ; plant uninjured. 



4. Rate: One and one-half lbs. per 1000 cu. ft. of space. 

 Time of exposure, 7 p. m. to 8 a. m. Plant treated : Tomato. Re- 

 sults : Plant uninjured ; adults apparently killed, but in the course 

 of two days about 20 per cent, recovered; about 10 per cent of 

 young larvae killed. 



5. Rate: Five lbs. per 1000 cu. ft. of space. Time of expo- 

 sure, 7 p. m. to 7.30 a. m. Plant treated: Tomato. Results: Plant 

 uninjured ; adults all killed ; 50 per cent of larvae and pupa; killed ; 

 eggs unaffected. 



Hydrocyanic Acid Gas. Cost of Potassium cyanide (KCN) 

 about 50 cents per lb. ; of Sulphuric acid (H 2 S0 4 ) from 2^ to 10 

 cents per lb. 



1. Rate: .1 gm. KCN per cu. ft. of space in a practically air 

 tight fumigating box containing 30 cu. ft. of space. Time of expo- 

 sure, 10 minutes, daylight. Temperature, 40 F. Plant treated: 

 Tomato. Results : Tender leaves killed and older leaves injured 

 at the tips ; all larvae were killed ; no pupae or adults present ; eggs 

 unaffected. 



2. Rate: .05 gm. KCN per cu. ft. of space in the same box 

 that was used in Expr. 1. Time of exposure, 10 minutes, daylight. 

 Temperature, 48° F. Plant treated : Tomato. Results : Plant 

 very slightly injured; very few larvae killed; eggs unaffected ; no 

 other stages present. 



3. Rate: .0016 gm. KCN per cu. ft.: 3 gr. in greenhouse 

 containing 1888 cu. ft. of space. Time of exposure, 6 p. m. to 8 

 a. m. Plants treated : Various greenhouse plants. Results : Plants 

 uninjured; adults were found to be stupified and fluttered about on 

 the benches ; all but about 5 per cent, recovered during the day. 



