16 BULLETIN 843, U. S. DEPARTMENT OF AGRICULTURE. 



time, early enough to secure a good crop before frost time. No 

 definite time can be assigned for early or late planting for the entire 

 range of this species; it is a matter for the growers themselves to 

 determine. Community work should accomplish much along this 

 line, in determining both the times for planting and the effect of 

 this method. 



It has been suggested that early planting be practiced in a com- 

 munity for a series of years and then late planting for a year or two 

 succeeding this. 



Whatever can be done toward lessening the number of insects in a 

 community during a given year will have a correspondingly greater 

 effect for the coming season. 



DIRECT MEASURES OF CONTROL. 



EXPERIMENTS WITH INSECTICIDES. 



Numerous spraying experiments were made with arsenate of lead, 

 Paris green, arsenite of zinc, and nicotine sulphate. The experi- 

 ments were conducted on moderately infested plots of string beans. 

 The spray was applied to both the upper and lower surfaces of the; 

 leaves with a portable compressed-air sprayer, fitted with an exten- 

 sion rod, elbow, and disk-type nozzle having a fine aperture. 



ARSENATE OF LEAD. 



Arsenate of lead was applied at the rate of 1|, 2, 2|, and 3 pounds 

 in powdered form in 50 gallons of water. The spray adhered well 

 and evenly to the foliage, but the effect was very uncertain on the 

 bean foliage as was also the killing effect on the insects. The injury 

 from burning varied greatly with the age and tenderness of the 

 plants, the older, tougher foliage usually escaping appreciable in- 

 jury, while on the younger, more tender plants the burning effect was 

 serious, especially where the stronger doses were applied. 



In summing up the experiments in spraying with powdered arse- 

 nate of lead the results were so uncertain that one is hardly justified 

 in recommending this insecticide as a reliable agent for controlling 

 the bean ladybird on string beans. 



One experiment was made with arsenate of lead paste at the rate 

 of 6 pounds to 50 gallons of water. This burned the beans so 

 badly that they were almost completely destroyed. Most of the 

 larvae were killed, but the majority of the beetles escaped injury. 

 This test indicates that paste arsenate of lead is even more in- 

 jurious to bean foliage than the powdered form, and that the killing 

 effect on the adults of the bean ladybird is equally uncertain. 1 



In experiments conducted by Merrill (21) in New Mexico pow- 

 dered arsenate of lead was used at the rate of 2 and 2| pounds to 50 

 gallons of water without damage to the plants. Most of the beetles 



1 The tests herein mentioned were conducted with standard or acid lead arsenate. 

 Neutral (diplumbic or triplumbic) lead arsenate, in experiments at Washington, J). C, 

 applied at standard dosage, caused no injury to bean foliage. 



