325 



trotizieri cannot become really valuable in the Dutch East Indies. 

 Pseudococcus citri, which lives on Castilloa and is protected during 

 the rainy season by the broad leaves of that plant, provides the 

 necessary medium for maintaining the stock. 



Peterson (A.). Some Soil Fumigation Experiments with Paradi- 



chlorobenzene for the Control oJ the Peach-tree Borer, Sanni- 



noidea exitiosa, Ssiy. —Soil Sci., New Brunswick, N.J., xi, no. 4, 



April 1921, pp. 305-318, 1 plate, 1 fig. 



The results obtained with sodium cyanide are briefly stated 



[R.A.E., A, viii, 309], and subsequent experiments with paradi- 



chlorobenzene for the destruction of Aegeria [Sanninoidea) exitiosa, 



Say, are described. This substance gives promise of becoming a 



valuable and important insecticide for the control of this moth. 



For the most part the results of similar experiments agree with 

 those obtained by Blakeslee [loc. cit. 189]. In the majority of cases 

 I oz. gave as good results as f and 1 oz. with the same exposure, i.e., 

 21 days or more ; smaller doses than this were, however, unsatisfactory. 

 Trees of six years and over are not seriously injured if the soil is warm 

 at the time of application. Slight injury to the bark may occur. The 

 effect on these trees at a soil temperature of 55° F. or less has 

 not been ascertained. So far no variation in the susceptibility 

 of different varieties of peaches has been noticed. Trees from 3-6 

 years old were successfully treated with \ oz. of paradichlorobenzene 

 with a 7 to 10-day exposure, about 80 per cent, of the larvae being 

 killed on the average with a 10-day exposure. Trees treated twice 

 in the summer proved free from borers in the autumn, winter, spring 

 and early summer, while those treated only in June were only free 

 from borers for six to eight weeks following the treatment. Early 

 spring treatment is not advocated owing to the low temperature of 

 the soil. The best time for New Jersey is from 25th August to 10th 

 September. The crystals should be evenly distributed in a circular 

 band between one and two inches from the tree. Should there be 

 any indication of borers in the tree 1 to 6 inches above ground, the 

 soil should be mounded about so that its upper level reaches the 

 highest point where the gum, containing sawdust-Uke particles, is 

 exuding from the tree. The application is made on this level. The 

 crystals are then covered with soil free from weeds, grass, stones, etc., 

 and this is packed down with the back of a spade. 



The present experiments indicate that soil texture does not have 

 much influence on the rate of evaporation, which is, however, retarded 

 should the soil be moist. As a rule evaporation is complete in from 

 6 to 8 weeks if the temperature of the soil is 60" F. or higher, and 

 the soil moisture is low. Further investigations are needed to deter- 

 mine the influence of moisture in long exposures. High soil tem- 

 peratures produce greater rates of evaporation than low ones. The 

 ineffectiveness of paradichlorobenzene at low temperatures is probably 

 also partly due to the consequent lower oxygen requirements of the 

 larvae. Fairly satisfactory results have been obtained at temperatures 

 ranging between 55" and 60° F. 



Phipps (C. R.). Control of the Pear Thrips.— A'. 1'. Agric. Expt. 

 Sta., Geneva, Bull. 484, January 1921, 11 pp., 5 plates, 2 tigs. 

 As soon as the adults of Taeniothrips inconsequens, Uzel {Pyri, 

 Dan.) appear in numbers, the ends of the buds should be thoroughly 



