19 



On potatoes, calcium arsenate dust gave excellent results against the 

 Colorado potato beetle [Leptinotarsa decemlineata]. The application 

 can be made with an orchard duster, without any special outlet for 

 distributing the material to each row ; but for extensive work it is 

 probably better to secure a special attachment. Calcium arsenate, 

 however, did not always give satisfactory results when used on fruit 

 trees. Lead arsenate is recommended for general use on all kinds of 

 fruits ; it gave uniformly better results than any other arsenate. With 

 magnesium arsenate there is a danger of severe foliage injurj^ to peaches 

 and apples, and a satisfactory control of codling moth [Cydia poynonella] 

 was not obtained with it. 



Dusting may be done when the foliage is either wet or dry. Some 

 growers prefer to dust at night, as atmospheric conditions are usually 

 more favourable. There should not be much wind. The material 

 should be applied from two directions for each application. A satis- 

 factory method is to dust down wind on two different days when the 

 wind is in different directions. There is usually a definite air current 

 at night. In ordinary circumstances it is not necessary to stop at 

 each tree. 



The cost of material is higher for dusting than for spraying, but the 

 cost of application is less. Dusting can be done much more rapidly 

 than spraying, and consequently it is possible to cover an orchard 

 quickly at critical times and to make extra applications when desirable. 

 No recommendations can be made as to dilute dusting mixtures at 

 present. Ordinary commercial sulphur is not suitable for dusting ; 

 only special dusting sulphur should be used. 



Foliage injury, which has sometimes been observed when spray 

 guns are used, can be avoided if proper care is taken. The driving 

 spray should be used as little as possible, the trees should not be 

 drenched, and the fine spray should always be used when covering parts 

 of the tree close to the operator. 



Pettit (R. H.) & McDaniel (E.). The Lecania of Michigan.— 



Michigan Agric. Expt. Sta., East Lansing, Tech. Bull. 48, March 

 1920, 35 pp., 7 plates, 16 figs. [Received 11th November 1920.] 



Of the genus Lecanium {sens, lat.) thirteen species and one variety are 

 described, including Tourney ella corrugatum. Thro., on Scotch and 

 Austrian pine and T. corrugatum var. neglectum, n., on pitch pine in 

 New York, and T. numismaticum, sp. n., on Scotch pine in Wisconsin. 



Jack (R. W.). The Bean Stem Weevil. A Minor Pest of Beans.— 



Rhodesia Agric. Jl., Salisbury, xvii, no. 5, October 1920, pp. 452-455, 

 2 plates. [Also published as Rhodesia Dept. Agric, Salisbury, 

 Bull. 369, October 1920, 4 pp., 2 plates.] 



The bean-stem weevil, Alcides leiicogrammus, Erich., here described, 

 occurs in various parts of Mashonaland. Its attack is apparently 

 limited to beans of the genera Phaseolus and Vigna (French beans and 

 cowpeas). The beetles feed on the stems and branches of the i)lants, 

 and lay their eggs in cavities that they have made at the base of the 

 stems. The larvae feed on the tissues at the base of the stem, and 

 tliough a single individual may be completely enclosed in the swollen 

 stem, when several are present considerable swelling and callus 



(7467-A) c 2 



