449 



to transport and difficult to store without loss. Attempts to prepare 

 it in the dry state have failed, as might have been expected, owing to 

 the calcium polysulphides decomposing on drying. Calcium thio- 

 sulphate, one of the ingredients of hme-sulphur, is not an efficient 

 insecticide, though soluble in water. Some other base is required, 

 as a sulphur carrier and it has been shown by Parrott and others, that 

 barium polysulpliides are equally effective with those of calcium, at 

 least in the control of San Jose scale {Aspidiotus perniciosus), and it is 

 an important practical fact that one of the barium polysulphides can 

 be produced in the form of soluble crystals, while those of calcium 

 cannot, and by boiling barium sulphide (BaS) in water with excess of 

 sulphur, a large quantity of the pentasulphide (BaS^,) is produced, 

 which, on drying, becomes converted into the tetrasulphide (BaS^H^O) 

 and free sulphur. This compound is readily soluble in cold water and 

 tables are given showing that the solution at various strengths of from 

 10 lb. to 32 lb. in 50 U.S. gals, water was equally effective with 

 lime-sulphur, with this further advantage that 32 lb. of the dry barium 

 product contains as much sulphur as 59 lb. (5| U.S. gals.) of the 

 lime-sulphur solution, and yet 16 lb. of the former in 50 U.S. gals, 

 water is sufficient to control the San Jose scale ; similar results were 

 obtained with the oyster-shell scale {Lepidosaphes idmi). Experiments 

 on peach trees showed that Cladosporium carpopJdlum was also com- 

 pletely controlled without injury to fruit or foliage. The cost in the 

 U.S.A. is estimated at a trifle more than that of Ume-sulphur, but this 

 is more than made up by difference in freight. 



McCoLLOcH (J. W.). Recent Results in the Use of Dust Sprays for 

 Controlling the Corn-Ear Worm. — Jl. Econ. Entom., Concord, vii, 

 no. 2, April 1915, pp. 211-214, 1 table. 



A study of the hfe-history of Chloridea {Heliothis) obsoleta, F., the 

 corn-ear worm, shows that complete control of the pest is impossible. 

 The larvae feed almost entirely within the curl of the maize plant or 

 within the ear, where they are out of reach of parasitic enemies or 

 sprays. They are able to develop on a great variety of plants ; the 

 adults can migrate readily from one field to another and the female 

 deposits from 500 to 2,000 eggs, the latter being laid singly and only 

 one on a plant. The method of spraying as a control measure has 

 been investigated. It was found that a large percentage of egga 

 deposited during the summer were placed on fresh maize silks and 

 that the caterpillars arising from these caused injury to the ear. It 

 thus seemed possible to control a large percentage of larvae by keeping 

 the silks well sprayed. Powdered lead arsenate was found to be the 

 most efficient poison. During the summer of 1914, the effect of dusting 

 \\'ith dry lead arsenate was determined. Using 100 per cent, lead 

 arsenate, 63 per cent, of the ears were injured ; with a mixture of 

 50 per cent, arsenate and 50 per cent, sulphur, the number of injured 

 ears amounted to 88 per cent. Although in the first case over 60 per 

 cent, of the ears were injured, in almost every case only 1 or 2 grains 

 on each ear were damaged and fungi were absent. A 63 per cent, 

 mixture gave results which were almost as good, at a much lower 

 cost. Hydrated hme would serve as a carrier instead of sulphur, and 



(C180) o 



