322 THE MONTHLY BULLETIN, 



Out of this thought the question arises: When, in relation to the 

 abundance of the pest, is the most economical time to adopt control 

 measures in order to prevent injury? In practically all cases where 

 scale insects are concerned, spraying is delayed until the pest is abund- 

 ant on the trees. The percentage of kill, when taken alone, has no 

 bearing whatever upon the effectiveness of the treatment. The factor 

 of importance is the number of living scales which are left after treat- 

 ment, not the percentage. A kill of 50 per cent would be equally as 

 effective as a kill of 95 per cent, if in the latter case the scale were ten 

 times as abundant as in the former. There would be left to reinfest 

 the tree for the next year an equal number of scales in either case. It 

 might be much easier to get a kill of 50 per cent in the one case than 

 95 per cent in the other. As a concrete example, it might be more 

 economical to treat for the brown apricot scale when it is comparatively 

 scarce in an orcliard and thus prevent it from ever becoming a pest, 

 than to wait until it is abundant before attempting control measures. 

 As a general rule, when a scale becomes sufficiently abundant to cause 

 the grower to consider remedial measures, it has already done much 

 damage. This damage might be avoided by the action suggested above. 

 There is, some place, a happy medium between spraying only when the 

 scale has become abundant and spraying every year regardless. Spray- 

 ing at that time could very properly be termed "preventive entomol- 

 ogy, '^ and its usefulness ought not to be difficult to demonstrate. 



One other phase of economic entomology might come under the head 

 of "preventive entomology," and that is the use of parasitic and preda- 

 eeous insects. Few entomologists nowadays will maintain that the 

 introduction of the enemies of an insect pest will entirely control it, 

 even under the most favorable circumstances. The ecological relations 

 of insects are such that perfect control by means of parasites is prac- 

 tically impossil)le. As Marchal says, the fluctuation in numbers of 

 host and parasites is the sine qua non of the existence of the species. 

 But the introduction of parasites and predators may have a very pro- 

 found influence upon the abundance of an insect pest by checking to a 

 certain extent its increase. The more enemies an insect pest has, the 

 less frequently will it reach the stage of abundance where artificial 

 means of control must be adopted, and it is along this line, wdiich 

 might well be termed preventive entomology, that the work of the 

 State Insectarv^ is being prosecuted at the present time. — H. S. S. 



Russeting of apples. — I am asked if I will rule that the russeting of 

 apples, as is so generally found in the basins about the stems of the 

 Newtown Pippins, is a "defect" in interpreting the apple standardiza- 

 tion law wliich l)ecomes operative August 8th. I answer a decided 

 "No." This russeting is a characteristic, not a defect. Beach in his 

 "Apples of New York" says in describing the Newtown Pippin: 

 "Cavity deep, acuminate to acute, broad or compressed, often sending 

 out rays of russet." As is well known, the Newtown Pippin in certain 

 localities of California is very generally marked with this russeting 

 about the stem. I suggest that reference to such characteristics be 

 made as "russet," not "rust." Rust usually refers to disease caused 

 by fungi, while the russet color is in no sense a disease, but is a color 

 the caiuse of which is oliscure. In many of the best fruits, like the 

 Golden Russet and the Roxbury Russet, the russetingc overs the entire 

 fruit. In the "Winter Nelis pear it is quite general and is often seen 

 in the Bartlett.— A. J. C. 



