EEPOET ON VAEIOUS METHODS FOE DESTEOYING SCALE 



INSECTS. 



By D. W. Coquillett, Special Agent. 



LETTER OF SUBMITTAL. 



Los Angeles, Cal., October 8, 1890. 



Sir: I herewith submit my annual report for the season of 1890. The Australian 

 lady-bird ( Vedalia cardinalis Mnlsant) recently introduced by this Division, success- 

 fully survived the winter unprotected out of doors, and as early as the month of 

 March I was able to distribute several colonies to those requesting them. Lest this 

 species, after exterminating the Fluted or Cottony-cushion Scale (Icerya purchasi 

 Maskell) should become extinct on this coast, our State Board of Horticulture, at the 

 suggestion of its president, Hon. Ellwood Cooper, has erected two propagating 

 houses over two large orange trees belonging to Col. J. E. Dobbins, in the San Ga- 

 briel Valley ; in these houses the Vedalias are to be propagated and distributed to 

 those requiring them. At the present writing it is no easy matter to find a single 

 living leery a anywhere in this part of the State, although in the early part of the 

 season they appeared in limited numbers in a great many places ; later in the season 

 the Vedalias also appeared in considerable numbers, and by sending colonies of these 

 to the different localities where the Iceryas had appeared, the latter were effectually 

 held in check. 



The Red Scale (Aspidiotus aurantii Maskell), so destructive to Citrus trees in certain 

 localities, is rapidly reduced in numbers through the agency of the treatment with 

 hydrocyanic acid gas, described in my previous reports. This treatment is now being 

 largely used for the above mentioned purpose, and is giving far better results than 

 have ever been obtained by the use of any kind of a spray ; numerous instances have 

 occurred where, upon large Citrus trees treated with this gas, neither myself nor other 

 parties were able to find a single living Red Scale, either upon the bark, leaves, or 

 fruit — a result which so far as I am aware has never been obtained by the use of any 

 kind of a spray. The cost of treating trees with the gas is scarcely greater than that 

 of using a spray, while the method has been so greatly simplified that trees can now 

 be treated with the gas very nearly as rapidly as they can be sprayed. I have not as 

 yet learned that any person, or even a single domestic animal, has ever been acci- 

 dentally injured either by the gas itself or by the materials used in producing it. All 

 of the objections which at first were urged against the use of this gas — the danger of 

 being poisoned by it or by the chemicals used, the great expense attached to its use, 

 and the impracticability of operating the tents— have finally been overcome, and the 

 treatment is now in successful operation. 



In my last report I gave an account of the spraying of a number of orange trees 

 at Orange according to instructions. These trees were not again sprayed until the 

 lapse of a little over one year. At this latter date the trees were again badly infested 



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