62 MASS. EXPERIMENT STATION BULLETIN 369 



already inside the fruit and more or less inaccessible. Growers in near-by states 

 where similar weather conditions prevailed had practically the same experience. 



Preliminary tests of insecticides for the protection of peaches from late-season 

 infestation were undertaken and some of the fixed nicotine compounds gave 

 promising results. 



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



Whitcomb and William Garland, Waltham.) Continued e.xperimental fumigations 

 with chlorinated naphthalene compounds showed that mi.xtures of chlornaphtha- 

 lene oil 3 parts and crystal naphthalene 1 part, or chlornaphthalene oil 3 parts and 

 chlornaphthalene soft wax 1 part, were noticeably more effective against red 

 spider on carnation than a mixture containing equal parts of chlornaphthalene 

 oil, crystal naphthalene, and paradichlorobenzene. 



The use of these materials, at the rate of J^ ounce per 1000 cubic feet for 6 

 hours on potted carnations in an experimental fumigation chamber equipped with 

 temperature and humidity control, showed that a temperature of 70° F. with a 

 relative humidity of 60 percent was more effective against red spider than tem- 

 peratures of 60° F. or 75° F. In twenty fumigations under these conditions the 

 two most effective formulas produced an average kill of red spiders of 98.5 and 

 99.5 percent in two successive fumigations, with several fumigations causing 

 complete mortality. No injury to potted carnations was observed from any of 

 these experimental fumigations. 



Control of the Common Red Spider on Greenhouse Plants. (W. D. Whitcomb, 

 William Garland, and W. E. Tomlinson, Jr., Waltham.) In previous experiments 

 and in commercial greenhouses the common red spider has been more difficult 

 to control on roses than on other greenhouse plants. Observations during Novem- 

 ber and December under normal greenhouse conditions showed that the average 

 period of development of the common red spider from the hatching of the larva 

 to the adult female was 11.7 days on Talisman rose, 13.8 days on gardenia, and 

 15.0 days on snapdragon. Similar studies at controlled constant temperatures 

 indicated that at 60° F., 70° F.. and 80^ F. the spiders required 14.25, 7.71 and 

 4.77 days respectively on rose, and 18.8, 8.80 and 6.75 days respectively on 

 gardenia. On carnation and snapdragon the development was intermediate to 

 the short period on rose and the long period on gardenia, but there were indica- 

 tions that under some conditions a longer period is required on snapdragon than 

 on gardenia. The development of spiders on ten varieties of roses showed no 

 significant difTerences when the greatest range was from 6.85 days on Souvenir 

 to 8.0 days on Templar. On Talisman rose, spiders laid an average of 3.49 eggs 

 per female, while on gardenias under identical conditions only 1.2 eggs per female 

 were laid. 



In spraying experiments conducted on bench roses under normal greenhouse 

 conditions, derris or cube powder containing 4 percent rotenone, emulsified with 

 sulfonated castor oil 1-300 and diluted at the rate of 2 and 3 pounds in 100 gallons, 

 gave only moderate control of red spider in three applications at weekly intervals 

 but good control after four applications. Derris was slightly more effective than 

 cube but there was no significant difference between 2 pounds and 3 pounds in 

 100 gallons of spray. Control of red spider was significantly better on Talisman 

 than on Templar, Premiere Supreme, or White Killarney. This spray left a 

 slight residue but caused no plant injury. 



In a second series, a dinitro compound prepared experimentally by Dow Chemi- 

 cal Company gave nearly perfect control on all varieties with no serious plant 

 injury. Cyclonox, a phenol preparation, gave good control when used in the 

 first application at 1-400 dilution but was only half as effective after a 1-600 

 dilution had been used in the three later applications. Plant injury was not 



