24 



BULLETIN 571, U. S. DEPARTMENT OF AGRICULTURE. 



trees made practically the same amount of growth during the course 

 of the season. 



Further fumigation experiments were conducted during March, 

 1916, and are reported in Table XXI. Only badly infested pecan 

 twigs were used in these experiments, and after being fumigated, 

 they were placed in water bottles in order to insure proper develop- 

 ment of the buds. 



Table XXI — Fumigation experiments on larvse of the pecan leaf case-bearer at Mon- 

 ticello, Fla., in 1916. 



Experi- 

 ment 

 No. 



Num- 

 ber of 

 twigs. 



Treatment. 



Date of 

 fumiga- 

 tion. 



Results. 



Remarks. 



I 

 II 



12 

 12 

 12 

 12 

 12 

 12 

 15 

 15 

 15 



Fumigated for 1 hour with h ounce 



of sodium cvanid ' per 100 cubic 



feet. 

 Fumigated for 1 hour with J ounce 



of sodium cvanid 1 per 100 cubic 



feet. 

 Fumigated for 1 hour with 1 ounce 



of sodium cvanid l per 100 cubic 



feet. 

 Fumigated for 1 hour with 1 ounce 



of sodium cvanid 2 per 100 cubic 



feet. 

 Fumigated for 1 hour with li ounces 



of sodium cvanid x per 100 cubic 



feet. 



191fi. 

 Mar. 4 



Mar. 3 



...do.... 



...do 



Larva? emerged 

 from hibernac- 

 ula. 



do 



All buds destroyed 

 by larvse. 



III 

 IV 



A number of larvae 

 emerged from 

 hibernacula. 



do 



were destroyed 

 by larvse. 

 Some buds were 

 damaged bv 

 larvse. 



V- 

 VI 



...do.... 

 ...do 



No larvse emerged 

 from hiber- 

 nacula. 



Larvse emerged 

 from hibernac- 

 ula. 



No larvse emerged 

 from hibernac- 

 ula. 

 do 



destroyed by 

 larvse. . 

 Buds didnotunfold 

 well. 



VII 

 VIII 



Fumigated for 1 hour with It ounces 



of sodium cvanid 1 per 100 cubic 



feet. 

 Fumigated for 1 hour with 2 ounces 



of sodium cvanid 1 per 100 cubic 



feet. 



Mar. 29 

 ...do 



stroyed by larvse. 



No injury to buds 

 from fumigation. 



No injury to buds 

 from fiimigation. 



IX 



...rlo 



Larvse emerged 

 from hibernac- 

 ula. 







by larva?. 



i Used formula 1-2-3. 



2 Used formula 1-1-3. 



It will be noted in Table XXI that strengths of sodium cyanid 

 of ^, f , and 1 ounce per 100 cubic feet failed to destroy the larva? 

 after one hour of exposure, while strengths of 1^ and 2 ounces per 

 100 cubic feet killed all larvse. It is to be regretted that in these 

 experiments a strength of 1J ounces was not used, as it was found 

 that while 1 ounce was not enough, 1^ ounces destroyed larvaB while 

 in the winter cases. Although the maximum strength used (1J 

 ounces per 100 cubic feet of space) is considerably in excess of that 

 commonly employed in the fumigation of ordinary nursery stock, 

 these experiments indicated that, while in a dormant condition, the 

 pecan was perfectly capable of enduring the greater strength without 

 injury. 



In fumigation for the pecan leaf case-bearer materials should be 

 used according to the following formula: 1-1^-2. This means 

 that 1 ounce (avoirdupois) of sodium cyanid, 1£ fluid ounces of 



