36 MASS. EXPERIMENT STATION BULLETIN 305 



laemiis montrouzieri Muls., can be secured from California at a very reasonable 

 cost. The adult beetles are shipped by air mail and several shipments have 

 been received in Massachusetts in good condition except during extremely un- 

 favorable weather in winter. Both adult and larval stages of this ladybug feed 

 on the greenhouse mealybug. 



In the greenhouses at the Waltham Field Station extremely heavy infestations 

 of mealybugs on gardenias have twice been satisfactorily controlled by liberating 

 Cryptolaemus beetles at the rate of about 1 beetle per plant. When the beetles 

 were liberated in January, the mealybugs were under control about 60 days 

 later. \\'hen the beetles were liberated in August, perfect control of a most severe 

 infestation was accomplished in 30 days. 



Preliminary studies of the relation of temperature to the development of 

 Cryptolaemus indicate that temperatures of 70° or above are desirable for efficient 

 activity. It required four times as long for eggs to hatch and pupation to be 

 completed at 60° F. as at 80°, indicating that these beetles will not thrive at low 

 temperatures. Isolated pairs lived four months at average greenhouse winter 

 temperatures and laid eggs intermittently throughout their whole life. The 

 maximum number of eggs laid by one paired female was 107. The estimated 

 increase from one generation in the greenhouse was 600 per cent. 



Naphthalene and Similar Materials as Greenhouse Fumigants. (W. D. 



Whitcomb, Waltham.) Experimental fumigations of chr\santhemum3 with 

 naphthalene have continued to indicate that this crop cannot safely withstand 

 this treatment. Injury is usually shown b\- blindness or deformed bud develop- 

 ment, and a varietal susceptibility is apparent. Major Bonnafon, Friendly 

 Rival, and Halliday are among the varieties most susceptible to naphthalene 

 blindness. 



It was also demonstrated that the fumes discharged during the first two hours 

 of a fum.igation are largely adsorbed by the plants, soil, and equipment, so that 

 the effect on red spider is negligible until after an exposure of three hours or 

 longer. 



Experiments with two commercial liquid fumigants in which the toxic benzene- 

 ring products are dissolved in a non-injurious solvent have shown them to be 

 effective for controlling red spider. Unlike crystal naphthalene, these fumigants 

 do not become injurious at the minimum temperature for growing greenhouse 

 plants, although their efificiency is decreased below 60" F". Most varieties of 

 plants which tolerate naphthalene fumes will tolerate these materials, but cucum- 

 bers have been severely injured in all experiments. 



Control of Red Spider on Greenhouse Crops. (W. D. \\ hitcomb, Waltham.) 

 Preliminary studies on the relation of temperature to the effectiveness of some 

 common commercial preparations used for combating red spider in the greenhouse 

 indicate that this factor exerts an important influence. 



On potted carnation plants an alcoholic extract of pyrethrum and soap gave 

 34 per cent greater kill of red spider at 60° F. than at 80°, and a 24 per cent 

 greater kill when additional soap was added. Another pyrethrum extract with 

 additional soap was 23 per cent more effective at 60° F. than at 80°. On the 

 other hand, a selenium preparation was 49 per cent more effective at 80° F. than 

 at 60°, while the effectiveness of a sulfur-carbon disulfide emulsion wis not 

 influenced by temperature. 



