Arizona republican., 1910-01-09
entomologist of the commission. It

entomologist of the commission. I
 says:
 In circular No. the subject of tn.
 influence of climatic conditions on in
 sects was discussed in a general way
 One of the principal points brought
 out was the fact that We have very
 little positive and exact information
 concerning the effect of climate upon
 insect life, especially the effect of such
 a climate as that of the Salt River
 valley. The writer contends that any conclusion concerning the effect of eli mate upon an insect when not very
 positive or very certain is not a prac- tical conclusion. When a mistaken conclusion may mean to be a promis- ing industry, such as citrus growing in Arizona, a setback more serious than
 the temporary setback produced by | the most severe freezes. 1t is incum- ! bent upon all who have interests to
 protect to understand thoroughly the evidence upon which conclusions must be based. This evidence in the case of the purple scale is practically the same as in the case of several other
 pests but the purple scale has been se- lected for this discussion on account of its being of greater interest as ex-
 plained in the preceding circular. What are the points which have
 been advanced as evidence that the
 purple scale cannot live in the Salt
 River valley? First it is said that the
 purple scale, or at least trees from
 sections infected by this scale. have
 been introduced for years without the
 pest having become eStablishde. Sec
 ond it is said that the purple scale
 does not thrive except in humid cli-
 mates and in California is not found except near the coast.
 To appreciate the value of these points as evidence we must under stand the conditions under which the insects become injurious. and we must also know the facts concerning the distribution, past and present, of the pest in California.
 In Florida and in California the pur- pie scale lives under entirely different conditions. In the former state the high average humidity tends to con trol the pest through the action of 1 fungus parasites: in the latter | the insect has attained it's high |
 NN 'N N6f't pl Dut IS | restricted to the interiors of | the trees. The writer~has seen at | Whittier. California, citrus trees which | were seriously injured by purple scale | but which appeared free from pests when the outside leaves only were ex- amined. Even where most destructive in California the survival of the pur- pie scale would not be expected if in fected trees were defoliated and set in open fields. Ii is not strange therefore that so far as observed, no live scale on infected trees planted in the Salt River valley last spring. The chances for crawling young to be car ried my other flying insects or by birds to the interiors of bearing trees is not great in any particular case: 1 put if those chances are indefinitely sooner or later the transfer ence is sure to occur. If once estab- ished in the interior of a bearing tree, iided perhaps by an unusually favor ible season to allow of gradual ac- the writer knows of no 'eason why the purple scale should not become serious pest here.
 In California this pest is gradually working eastward away from the coast md now occurs near to the San Ber- lardino county line. The progressive :itrus growers in San Bernardino and Riverside counties consider that they Ire dependent upon their efficient horticultural commissioners ather than upon climatic conditions or their present immunity from the 'cale as can be found anywhere in
 To establish a proposition that the Salt River valley is unfavorable to the purple scale some definite evidence must be produced. As regards the lumber of years during which the cit us trees of the Salt River valley have ( ,een exposed to infestation by this in any one prove that any in- ested trees were introduced previous { O five years ago? Does any one know l hat live purple scale larvae have ever ( ,een transferred into the interiors of bearing trees in this valley? Does any me know that they would not be so transferred this year or the year fol- owing if infested nursery trees were ,lented here? Does any one know that .ither the summer of 1910 1911 or 1920 will not be noted for the coldest and most humid summer ever recorded. condition as favorable or the establishment of the purple Icale as can be found anywhere in Florida or California? Finally, does my one know that if the purple scale were allowed to take advantage of iuch a climatic condition. it would not become so acclimatized that upon the'