CONTROL OF CYCLAMEN AND BROAD MITES ON GERBERA 9 



Results of tests to determine the length of the hot-water treatment 

 required to kill the mites on plants in the wire-mesh tray are given 

 in table 1. A high percentage of mites was killed by a 10-minute 

 immersion and a complete kill was obtained by an immersion of 15 

 minutes or longer. The mites that survived the 10-minute immersion 

 were located in pubescence and in folds of young leaves or beneath 

 bracts in flowers, whereas those in similar locations were killed by the 

 15-minute treatment. Because of injury to certain varieties of gerberas 

 resulting from longer immersion, as discussed later, it is not advisable 

 to treat them for more than 20 minutes. 



Figure 7. — Metal-lined tank, approximately 3% feet deep, 6 feet wide, and 12 

 feet long, outside dimensions, fitted with hand-controlled steam lines and screen 

 tray with cover, used for immersing gerbera plants. 



VAPOR-HEAT TREATMENT 



Control of the cyclamen mite on gerbera by vapor-heat treatment 

 was investigated with the available equipment at Washington, D. C, 

 and at Babylon, X. Y., and the results are given in table 1. The treat- 

 ment by vapor heat requires a specially constructed apparatus that 

 heats the air to the desired temperature by means of electricity or 

 steam and at the same time completely saturates it with moisture. In 

 these tests in which plants in thin layers were exposed for periods of 

 from 5 to 60 minutes at 110° F., a treatment for 30 minutes or longer 

 gave a complete kill of all mites. A treatment for 60 minutes is prob- 

 ably advisable because of even greater assurance of a complete kill 

 since, as shown in tests with several varieties, only the most tender ones 

 are injured even slightly by this treatment. 



