210 EXPERIMENTAL FARMS. 
seriously the question of remedies, making it necessary to apply several successive treat- 
ments, if it is hoped to thoroughly free a plant infested by this enemy so difficult to 
‘conquer. 
The mere fact of a scale-insect occurring, even in vast numbers, upon a given plant 
does not necessarily prove that the species is a dangerous enemy to that kind of plant ; 
for, although it may possibly be so and should be regarded with suspicion, this habit of 
occurring in great numbers on isolated trees, but on no others surrounding these, has 
frequently been noticed with scale-insects, and is probably due to some lack of vigour in 
the individual tree. In the case of the San José Scale, on the other hand, if other trees 
are reasonably near, it is almost certain that they will soon become infested ; and, when a 
severe case of infestation is found, one of the first things looked for when considering 
whether the pest is actually the San José Scale or one of the other species which super- 
ficially resemble it very closely, is, whether surrounding trees are also infested. 
This important difference of habit in spreading and the much more fatal effects 
upon trees from the presence of the San José Scale, make much more stringent measures 
necessary to secure its eradication than with many other species, even frequently render- 
ing it advisable or imperative to destroy many trees, if not whole orchards. This being 
the case, the very great advantage is obvious of being perfectly sure as to the identity 
of an infesting scale-insect before valuable trees are condemned to destruction. 
Unfortunately, as stated, there are several species of scale-insects which bear a 
very close superficial resemblance to the much to be dreaded San José Scale. On this 
point, which has been referred to by many entomologists, Mr. T. D. A Cockerell, a 
high authority, may be cited: “It has been a matter for dispute whether the San José 
Scale can be certainly recognized in the field. Its effect on thetree, killing the branches, 
is characteristic, but hardly in any sense diagnostic, while the reddening of the tissues 
of the plant adjacent to the scale is sometimes well marked with A. ancylus, as well as 
with perniciosus. <A little experience, however, enables one to recognize the ashy gray, 
generally thickly massed scales of perniciosws, with the dot and ring of the male scale, 
as against the dark scale and contrasting reddish orange exuviz of ancylus, or the 
similar scales of ostrewformis and Forbesi. At the same time, it is to be recommended 
that the diagnosis made in the field be in every case confirmed by examination of the 
insect under the compound microscope if either locality or plant is new.” (Technical 
Series, Bull. 6, U. S. Div. of Ent., 1897.) 
The above is from a valuable pamphlet prepared under Dr. Howard’s direction for 
the special purpose of helping students to distinguish between these different scale- 
insects. Prof. F. M. Webster says: “I know of no insect the detection of which has 
given expert entomologists more trouble than this one. Its extreme minuteness, its 
close resemblance to the other species less harmful, and the frequency with which it is 
found concealed in cavities and about the wrinkles of the bark or under buds, render 
its detection, when present in limited numbers, a matter of extreme difficulty.” (Ohio 
Bulletin 81, p. 183.) 
For the exact separation of these closely allied species it is necessary to take the 
females from beneath the scales and examine them under a microscope after special 
preparation. The differences are then readily seen, but these are beyond the power of 
ordinary pocket lenses or magnifying glasses, and require compound microscopes, which 
are expensive instruments not in the hands of ordinary fruit growers, and for the use of 
which special knowledge is needed. 
; As, therefore, there are several kinds of scale-insects resembling each other so 
closely at first sight as to make it necessary for even expert entomologists to examine 
them with a microscope before being positive as to the identity, and as one of these, to 
wit the San José Scale, is extremely injurious and the others not nearly so much 
so, we invite all fruit growers to send for examination and report specimens of any 
suspicious scale-insects which they may find upon their trees before they adopt extreme 
measures or even decide upon what measures they will take to free their orchards. Not 
only does the San José Scale spread more rapidly than many other species, but it has 
been found much more resistant than others, to the ordinary applications used for scale- 
insects. 
