FUKGOUS AND OTHER DISEASES. 69 



It is evident, from the records of true parasites given at the outset, 

 that native parasites are beginning more and more to attack the San 

 Jose scale. The native predaceous beetles will follow suit, and un- 

 doubtedly as 3^ ears go on the seriousness of San Jose scale infestation 

 will diminish, as, in fact, it has already done in California and perhaps 

 noticeably also already in some sections in the East. 



FUNGOUS AND OTHER DISEASES OF THE SAN JOSE SCALE. 



Scale insects are more or less subject to control b}^ fungous and 

 other diseases, and the San Jose species is no exception to this rule. 

 Control by these agencies is particularly efficient in the moist Tropics, 

 so much so that most scale insects are practically wanting in such 

 regions. The armored scales, such as the San Jose scale, are rarely to 

 be met with in tropical regions in any numbers, and where found are 

 diseased in a large percentage of cases. The mealy bugs, however, 

 are comparatively immune. The efficiencj^ of these diseases as a means 

 of control lessens as one leaves the Tropics, but in the subtropical 

 regions of the United States, and even in the temperate regions, the San 

 Jose scale has in many instances been very generall}^ exterminated by 

 disease. Several of these diseases are obscure and have never been 

 scientifically studied, nor have they developed any fruiting stage so 

 that they could be studied with any degree of accuracy. 



In the early work with the San Jose scale in California, Mr. Coquillett 

 reports the death of the San Jose scale from an unaccountable cause, 

 supposedly disease, in Pasadena County, Cal., on pear trees which 

 had not been treated with any kind of insecticide. Specimens of 

 twigs covered with dead scales were submitted to the Bureau of 

 Plant Industry for examination. No specific disease germ could be 

 discovered, but this does not preclude the explanation of some definite 

 disease as the cause of the death of the scales. Similar cases have 

 come up in the East several times, the first perhaps occurring at Riv^er- 

 side, Md., in the earl}^ history of the scale, where, without treatment, 

 the scale died in a very large percentage thruout a considerable orchard. 

 A number of similar cases were reported b}^ Doctor Howard in Bul- 

 letin 12, one from Tifton, Ga., where a careful count of the scales 

 showed that on one twig out of 183 scales 4 were living; on a second, 

 out of 723 scales 2 were living, and on a third, out of 579 scales 28 

 were living, giving 34 living scales out of 1,485, a mortality rate of 

 97.7 per cent. A similar case was reported also from Wadle}^ Ga., 

 by Professor Starnes, and Professor Alwood has noted the same con- 

 ditions at Vienna, Va. Doctor Howard also records the fungus- 

 infested scale reported by Doctor Fletcher at Fruitland, Ontario, altho 

 here the fungus or disease is probably a difierent one. 



A more promising and important disease of the San Jqse scale is 

 the cosmopolitan scale-insect parasitic fungus Sphaerostilba coccophila^ 



