Coccidae 329 



There are several attendant troubles in the growing of the host plant 

 material, the more important of which are "tip burn" or "tip dieback"; 

 damping-off due to Rhizoctonia; aphis, and potato tuber moth. "Tip 

 burn," which affects the sprouts soon after they are out of the ground, 

 produces numerous weak laterals, which in turn are themselves often 

 affected. Its cause has not been determined. It is, however, believed to 

 be entirely physiological and due to a combination of conditions in the 

 rooms, particularly relating to ventilation and humidity. 



Damping-off is induced by overwatering and slow evaporation, in spite 

 of the fact that each tray is drained through a %-inch crack through the 

 entire length of its bottom and that care is taken to avoid saturating the 

 soil. Some insectary operators report successful control of damping-off 

 by spraying with Semesan, but in general it may be prevented by avoid- 

 ing the humid conditions which favor it. Rhizoctonia usually gains access 

 because of non-elimination of infected seed when planting. It girdles the 

 sprouts at the surface of the soil and, if it does not kill them immediately, 

 it so weakens them that they soon succumb to the attack of the mealybug. 



The common mealybug (Pseudococcus citri) is best adapted to labora- 

 tory production. This fact is due to its restricted migratory habits, its 

 inclination to remain on its host even under over-infested conditions, its 

 short life cycle under laboratory temperatures, and a possible high de- 

 gree of infestation with least injury to the potato sprouts. 



An ample supply of mealybugs should be made available for evenly 

 infesting the host plant material as it matures. 



Infestation of the sprouts is accomplished through the use of temporary 

 host material such as the stems and leaves of sunflower and mallow. This 

 material is distributed over trays of hatching mealybugs and left there 

 until completely infested. It is then collected and placed on new trays 

 of sprouts to which the bugs migrate as the temporary host dries. The 

 proper degree of infestation is determined by experience. 



When mealybug material is collected in the field and used to infest the 

 sprouts it should be placed in cloth bags or perforated paper sacks to per- 

 mit the egress of the young mealybugs and retain any parasites that may 

 be present. 



METHODS USED IN REARING THE MEALYBUG, 

 PSEUDOCOCCUS COMSTOCKI 



W. S. Hough, Virginia Experiment Station 



TWO methods were used in rearing Pseudococcus comstocki on ca- 

 talpa: the vial method, and by using potted seedlings 6 to 18 inches 

 in height. In the vial method I used straight edged vials i-inch in 

 diameter and 4 or 5 inches long. Either a newly hatched mealybug or 



