285 



grain insects is in a condition comparable with that of milled products, 

 and is subject to attack by the milled product insects. Moist and 

 mouldy products are subject to attack by fungus-eating insects. Each 

 insect seems to have a very definite moisture requirement. The 

 nutritive value of the material may influence the rate of growth and 

 percentage of survival of the insects. The work on nutrition is to be 

 continued. 



A study of arsenicals has been made, working on the assumption 

 that leaves of plants when wet exhibit a negative electrical charge, 

 and that the arsenicals used at the present time also exhibit a negative 

 electrical charge. It is believed that if an arsenical could be prepared 

 with a positive electrical charge, greater adherence to the foliage 

 would result. Such material could be prepared cither by the addition 

 of electrically positive material, such as ferric hydroxide or aluminium 

 hydroxide, to the ordinary negative reaction, or by the preparation of 

 such arsenicals as ferric arsenate or arscnite or aluminium arsenate 

 or arsenite, with positive charges, thus accomplishing the result 

 directly. A full report of the results will be published shortly. 



As regards the spreading of sprays over the leaf surface, the rule 

 seems to hold good that spreading will occur if the surface tension of the 

 leaf is greater than the sum of the surface tension of the spray material 

 plus the surface tension at the interface of the spray and the leaf. 

 On leaves with a thick cuticle excellent results could be obtained by 

 using I lb, casein to 100 U.S. gals, of water, the casein being dissolved 

 in a small amount of sodium hydroxide. Gelatine or an alkaline 

 solution of flour used at the same rate can also be employed. On 

 waxy leaves the difficulty of obtaining satisfactor}^ spreading is being 

 overcome by the use of substances that have a decided affinity for the 

 wax of the leaf. 



SxAPP (O. I.) & Pierce (L.). Experiments in Dusting and Spraying 

 Peaches for the Control of Curculio, Brown Rot and Scab. — 



]\fississipiyi Agric. Expt. Sia., Agric. Coll., Bull. 195, December 

 1920, 8 pp. [Received 16th April 1921 .] 



The peach Curculio [Conotrachclus nenuphar] M^as the cause of 

 50 to 60 per cent, loss among peaches in unsprayed orchards in 

 jNIississippi during 1920. A number of spraying tests are recorded in 

 which both dust and liquid mixtures were tried against this weevil, 

 and against brown rot and scab. As regards dusting, the necessity for 

 fineness of materials and for proper and thorough mixing is emphasised, 

 and for this purpose a mechanical sifter and mixer is recommended. 

 Three applications of 10 per cent, lead arsenate dust were effective 

 against the insect, but caused considerable injury to foliage ; 5 or 

 8 per cent, lead arsenate seems to be the highest percentage that 

 can be used with safety, and proved almost as efficient. On the whole 

 it is considered that while dust sprays will probably prove the more 

 efficacious against diseases, liquid sprays give the best result against 

 the weevil. The applications recommended for use on healthy trees 

 on fertile soil are 1 lb. lead arsenate powder to 50 U.S. gals, water, 

 with 5 lb. unslaked lime to be used immediatelv after the blossoms 

 have fallen ; the same spray ten days later ; self-boiled lime-sulphur 

 8 : 8 : 50 with 1 lb. lead arsenate powder about two weeks later ; 

 and self-boiled lime-sulphur 8 : 8 : 50 about four weeks before the 

 fruit is expected to ripen. 



