July J. 1917 Life History of Plutella maculipennis 9 



CONTROL MEASURES 



During the years 1 909-191 6 the writer made many insecticide experi- 

 ments to determine the best means of controlUng the various "worms," 

 including the larvse of the diamond-back moth, which infest cabbage and 

 related vegetables. Tests were made with Paris green, arsenate of 

 lead, zinc arsenite, nicotine sulphate, and soap solutions. In the writer's 

 experience the following mixture, appUed as a spray, is unquestionably 

 the most effective remedy against the larvae of the diamond-back moth 

 on cabbage. 



Paris green pounds. . 2 



Soap do. ... 6 



Water gallons. . 100 



In small plantings this mixture may be applied with a portable com- 

 pressed-air knapsack sprayer, fitted with an extension rod, elbow, and 

 a nozzle of the disk or Vermorel type having a fine aperture. The 

 application should be thorough, and, as an adhesive is required, owing 

 to the waxy "bloom" of the leaves, common laundry soap will be found 

 satisfactory and is always cheap and available. 



Powdered arsenate of lead, applied at the rate of 4 pounds in 100 

 gallons of water, is another effective remedy for worms on cabbage and 

 at present, owing to the abnormal conditions brought about by the 

 war in Europe, is cheaper than Paris green. 



Unfortunately considerable prejudice exists against the use of arsen- 

 icals on cabbage. This feeling is groundless and should be discouraged. 



CONCLUSION 



The diamond-back moth (Plutella maculipennis) is a cosmopolitan 

 species widely distributed in the United States. The larvse are slender, 

 green "worms" which infest many varieties of cruciferous plants but 

 seldom cause appreciable injury to any except cabbage, cauliflower, and 

 rape. At Rocky Ford, Colo., seven generations, or broods, develop annu- 

 ally. The life cycle from egg to adult is passed in from 16 to 47 days. 

 In the Southern States this insect is active throughout the year. 



Although it develops with remarkable rapidity and is capable of caus- 

 ing extensive damage if unchecked, the diamond-back moth is so effect- 

 ively held in repression by parasites that it rarely becomes more than a 

 minor pest. Whenever the parasites are inactive and the larvae become 

 sufficiently numerous to demand attention, they may be readily con- 

 trolled by spraying the infested plants with an arsenical. 



