28 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE. 



The calcium cyanamicl analyzed about 17 per cent ammonia, this making the 

 amount of plant food in the treated and check rows practically the same. The fer- 

 tilizer was applied 14 days before the plants were set, as calcium cyanamid has the 

 effect of stunting tobacco plants if applied directly before planting. It jwas applied 

 to the rows with a drill, and thoroughly mixed with the soil by running a cultivator 

 over the rows. The plants were set on June 8. By June 30 the plants in both treated 

 and check rows had been almost completely destroyed by the Crambus larvae, there 

 being no indications of any beneficial effect from the calcium cyanamid in preventing 

 injury. The tobacco was not replanted. 



LEAD ARSENATE AXD PARIS GREEN USED WITH COAL TAR OX SEED CORX TO PREVENT 

 INJURY BY CRAMBUS LARV.E. 



Experiments in the use of arsenate of lead and Paris green with coal tar on seed 

 corn to prevent injury by Crambus larvae were conducted in 1910 on the J. F. Pur- 

 dum farm. 



In experiment A, arsenate of lead in paste form was used at the rate of 1 ounce to 

 1 gallon of water. One peck of shelled seed corn was allowed to soak in the solution 

 about 10 minutes and dried by mixing with fertilizer (acid phosphate). A very little 

 coal tar (about a tablespoonful) was then poured on the corn, which was thoroughly 

 stirred until a thin coating of the tar covered each kernel. Fertilizer was then used to 

 dry the tar. With an ordinary planter one-half acre was planted in seed prepared as 

 just described. Fully one-third of the corn failed to germinate, possibly owing to 

 exclusion of moisture from the seed by the tar, as the weather was dry. No benefit 

 in preventing injury by the worms seemed to result. In the check plat the stand 

 of corn was practically perfect. On June 16, four weeks after planting, a count was 

 made in the treated and check plats of hills of corn showing Crambus injury. Eleven 

 per cent of the hills showed injury in the treated plat and 13 per cent in the check 

 plat. 



In experiment B, 1 ounce of Paris green was used to 1 peck of shelled seed corn. 

 A small amount of tar (about one tablespoonful) was poured over the corn, which 

 was thoroughly stirred until a thin coating of tar covered each kernel. The corn 

 was then dried by mixing with fertilizer to which Paris green had been added. One- 

 half acre was planted with seed prepared in this manner. About one-fifth of the 

 seed failed to grow. In the check plat the stand was practically perfect, 



A count of hills of corn showing Crambus injury, made on June 16, four weeks 

 after planting, showed the results of the treatment to be as follows: Injury in treated 

 plat, 11 per* cent; injury in check plat, 9.5 per cent. 



SUMMARY OF ECONOMIC CONTROL. 



(1) The eggs of the tobacco Crambus are deposited in weedy fields 

 during July and August. They hatch in a few days. The larvae 

 remain over winter in the soil and complete their growth during 

 June and July. They are in their most active feeding stage at the 

 time tobacco or corn is planted. 



(2) Injury to tobacco or corn occurs when these crops are planted 

 on land which was weedy during the previous year. Crops planted 

 on land which has been under clean cultivation are immune from 

 injury. 



(3) The weeds which have been found to be the more common 

 natural food plants of the worms are the buckhorn plantain, oxeye 

 daisy, stickweed, and whitetop. The presence of these weeds in 

 meadows accounts for injury to tobacco or corn when planted on sod. 



