244 



Among Lepidoptera, the Noctuid, Alabama argiUacea, Hb., acts 

 indirectly as a control ; when this species becomes abundant on cotton 

 in late September or October, the caterpillars devour every vestige 

 of cotton foliage, eating the red spiders together with the leaf-tissue, 

 while those that are not actually devoured at the time of defoliation 

 are compelled to seek new hosts by migrating. 



Tables are given recording the rates of feeding of the principal 

 enemies mentioned. 



Preventive measures include clean culture, and the extermination 

 of winter hosts and of all weeds and plants on which the pest feeds. 

 Violets especially, when grown near cotton, should be watched and 

 sprayed or destroyed if found to be infested. A finely pulverised 

 surface mulch maintained on the fields may retard the migration of the 

 mites and so limit the infestation. Trap-crops, rotation, irrigation, 

 etc. , have been proved to be of slight or negative value. The following 

 insecticide sprays have all been used with successful results : Potassium 

 sulphide, 1 oz. to 2 U.S. gals, water ; kerosene emulsion, 2 gals, kerosene 

 to 12 gals, water ; lime-sulphur (home-made and commercial) ; 

 commercial misicible oil in a strength of 1 : 20 ; water-soluble oil ; 

 resin wash, consisting of 2 lb. resin, \ lb. caustic soda, \ pint U.S. fish- 

 oil to 10 U.S. gals, water. This is an excellent spray for red spider, 

 but is not prepared quickly or easily. Nicotine sulphate \ oz., to 

 \ lb. fish-oil soap with 2 U.S. gals, water was found a perfect spray, 

 and nicotine sulphate (1 to 500) and a miscible oil (1 to 40) also caused 

 complete mortality. A simple adhesive spray made of laundry starch 

 converted into paste and diluted with water deserves further con- 

 sideration. Fish-oil soap, \ lb. to 2 U.S. gals, water also caused 

 complete mortality. In spraying, it is necessary to hit the entire 

 underside of every leaf of an infested plant, and, since none of the 

 above sprays destroys the eggs, a second spray is essential to kill the 

 mdividuals that were in the egg-stage at the time of the first spraying. 



A bibliography of 91 works is given. 



Sasscer (E. R.). Fumigation of Ornamental Greenhouse Plants with 

 Hydrocyanic-acid Gas. — U.S. Deft. Agric, Washington, D.C., 

 Bull. no. 513, 10th March 1917, 20 pp., 4 figs. 



This paper gives detailed directions for fumigation with hydrocyanic- 

 acid gas. A table is given of the greenhouse plants which are most 

 easily injured by the gas, the pests controlled, and the cjuantity of 

 gas per 1,000 ft. which can be used without causing any damage to 

 plants. For each ounce of sodium cyanide, 1| U.S. fluid oz. of sulphuric 

 acid should be used with 2 U.S. fluid oz. of water. The water should be 

 measured out first into each generator, then the acid should be added 

 and lastly the cyanide should be gently dropped into the warm water 

 immediately before leaving and closing the greenhouse. A short 

 exposure lasting one or two hours with a more concentrated gas has 

 been found more satisfactory than a weaker gas used throughout the 

 night. The effects of weather conditions on fumigation are discussed. 

 The temperature should be between 55° and 70° F. Fumigation during 

 sunshine is liable to cause injury to the plants. Excessive moisture 

 in the greenhouse decreases the effectiveness of the gas, owing to its 



