42 



Malenotti (E.). Esperimenti fatti inSicilia neri917 contro la Bianca- 

 rossa degli Agrumi {Chrysomphalus dictyospermi, Morg.). — 

 — [Experiments made in Sicily in 1917 against C. dictyospermi, 

 Morg.] — Ministero per V Agricoltura, Rome, 1918, 8 pp. 



This report describes work on a large scale undertaken as a result 

 of experiments conducted in 1914 with colloidal calcium polysulphide 

 [see this Review, Ser. A., iv, p. 143]. The orange trees were examined 

 on 12th December 1917, 4| months after the last spraying, and the 

 destruction of Chryso?nphalus dictyospermi was found to be absolute 

 on very many leaves. Any exception to the general highly satisfactory 

 result was due to lack of skill in spraying. The fruits were quite free 

 from infestation and markings. Untreated trees near the experiment 

 plots were on the other hand very heavily infested. It is pointed out 

 that infestation causes a loss of from 8 to 12 shillings per 1,000 oranges, 

 the corresponding cost of spraying being under 5 pence. 



Jones (T. H.) & Gillette (C. P.). Life-History of Pem,phigus populi- 

 transversiis.—Jl. Agric. Research, Washington, D.C., xiv, no. 13. 

 23rd September 1918, pp. 577-594, 5 plates, 1 fig. [Received 

 21st November 1918.] 



As a result of investigations made in the field and laboratory at 

 Baton Rouge, Louisiana, much valuable information has been gathered 

 regarding the life-history and habits of Pemphigus populi-transversus. 

 The weather influences to a large extent the dates of appearance of 

 the various stages and the migration of this Aphid. Galls formed 

 by the stem-mothers begin to develop on the petioles of the young 

 leaves of Populus deltoides in the spring. They increase in size during 

 the summer and by the time the leaves fall in the autumn reach 

 their greatest diameter of nearly an inch. In July 1916, the percentage 

 of leaf -petioles of P. deltoides infested with the Aphids was found to be 

 25*2 out of 1,175 leaves examined, these being taken from both large 

 and small trees. Winged migrants of P. populi-transversus have been 

 found in the galls as early as 1st June, the percentage of galls containing 

 winged migrants, as well as the number in each gall, increasing as the 

 season advances. These winged migrants from the galls fly to various 

 cruciferous plants, and have been found on the leaves of these as early 

 as 30th August, and as late as 31st October. The greatest migration 

 probably takes place during October. Though the maximum distance 

 they can traverse in flight is not known, it is probable that they, as 

 well as the sexupara, may be carried long distances by wind. The 

 winged migrants give birth to viviparous females that start colonies 

 on the roots of crucifers, upon which they feed. They have been found 

 at the roots of cabbage, turnip, Brussels sprouts, rape, Coronopus 

 didymus (a weed that is sometimes eaten), and Roripa sp. While 

 a severe infestation of P. populi-transversus on the roots of crucifers 

 may be indicated by the wilted condition of the leaves, a slight or 

 moderate infestation is scarcely noticeable in the portions of the 

 plant above ground. A white, cottony material secreted by the 

 Aphids generally becomes apparent about the roots of the plants. 

 In the spring the winged migrants fly from crucifers to poplar trees, 

 where they give birth to sexuales, which are usually found in crevices 



