March, 1934J Agricultural Research in N. H. 19 



to the real objective sought when a so-called wetting agent is added 

 to a contact insecticide. The importance of accomplishing rapid spread 

 over the body of an insect is often lost sight of and attention is cen- 

 tered on spread over leaf areas. While the latter has a definite place 

 in the optimum performance of a given material, it remains true that 

 spread on the surface of an insect is of particular significance. 



Data already accumulated by the department indicate that a wet- 

 ting agent may not give the same desirable performance on an insect 

 that it gives on a leaf, and that important factors enter into this, in- 

 cluding such items as the nature of the leaf surface on which a given 

 insect happens to be feeding. 



Since the department has excellent facilities for an accurate study 

 of this question, utilizing photomicrographs of angles of contact, an 

 investigation has been undertaken. It is expected that this will be 

 concluded at an early date, and that results will be ready for publi- 

 cation as No. VII in "Studies of Contact Insecticides." 



In the course of the year the department has helped to develop 

 some new contact insecticides which utilize the principle of providing 

 a chemical medium which affords optimum contact qualities and which 

 serves as a carrier for relatively small amounts of an added toxic sub- 

 stance, such as pyrethrins, the two together operating to reenforce each 

 other, and thereby to provide a spray that is relatively toxic to an in- 

 sect and, at the same time, relatively safe to plants. {Purnell Fund) 



Burgundy Not Always a Substitute for Bordeaux 



Burgundy mixture is a copper fungicide ranking next to Bordeaux 

 in importance, but not so generally applicable due to its particular 

 properties, according to research concluded by 0. Butler. When a 

 Bordeaux mixture containing an excess of lime is desirable, for in- 

 stance, Burgundy cannot be substituted because the translucency of 

 the dried Burgundy spray is not materially affected while that of the 

 Bordeaux is. But when a highly translucent material is required — 

 as in spraying plants that are to be inspected for mosaic — the Bur- 

 gundy may be used in place of the Bordeaux. 



After studying several formulae recommended for Burgundy, the con- 

 clusion is that a mixture combining equal weights of copper sulphate 

 and crystallized sodium carbonate will prove most satisfactory. 



The fact that sodium carbonate loses water on exposure to air is 

 not considered important since stock solutions will be used in prac- 

 tice. The strength of the latter can be checked by weighing or by 

 using an hydrometer. 



Burgundy mixture deteriorates more rapidly on standing than does 

 Bordeaux, but can be stabilized even more effectively than the latter. 

 {Adams Fund) 



Lime-Sulphur Apple-Scab Spray Injury 



It may be inferred from certain orchard practices that the rate of 

 drying of a lime-sulphur spray used for control of apple scab, has an 

 efTect on the injury produced. Some experiments were made with 



