476 ANNUAL REPORT OF THE Off. Doc. 



WHY IS IT NOT WORSE? 



With aj?i'icnllural practices as we have described them, provid- 

 ini? favorable breeding places for this |)eriilcions insect during the 

 whole period of time which it develops with volunteer wheat, which 

 begins to germinate soon after harvest and only stops with the coming 

 of winter, is it not a wonder that our wheat fields are not annually 

 devastated by this insect? That they are not so devastated is due the 

 parasitic enemies of this fly, which keep on its heels so closely that 

 it is seldom abundant and destructive for more than a year at a 

 time. Here is a field for investigation and original research as to 

 how the farmer may co-operate with these parasitic enemies of the 

 Hessian fly in his agricultural operations that it may never be abun- 

 dant and thus save millions to the State and nation. 



ANOTHER WHEAT PEST 



The wheat midge (Diplosis Tritic) seems to have api)eared in some 

 sections of the State. The larvae of this insect comes from an egg 

 deposited by the adult midge in June, in the blossoms of very young 

 kernels of the wheat head and feeds upon the kernel and dwarfs it 

 or causes its entire abortion. Deep plowing and either packing 

 the chaff or using it for roughage will keep down this insect. 



SPRAYING MIXTURES 



In my rej ort of 1910 I referred to the injurious effects of some 

 insect and Umgicide spray mixtures especially fungicides. It has 

 been assumed that solid bodies can not enter the epidermis of healthy 

 plants, and so far nothing has developed to show that they can, and 

 with this assumption not disapproved the question naturally arises 

 why then do arsenical sprays that have been regarded insoluble in 

 water injure foliage. The fact that under the conditions of solubility 

 as tested by the chemists in which a substance is exposed to the 

 action of the solvent, which is pure distilled water, for a compara- 

 tively short time the substance may be insoluble, but the same salt, 

 when exposed for whole nights and days at a time to water com- 

 pletely saturated with the gases of the air or in natural water such 

 as is used for prej)aring spray mixtures and usually containing 

 chlorides, carbonates, sulphates, etc., of the alkali and alkali earth 

 metals in quantities as these in natural water these arsenicals become 

 soluble. This is especially true of the arsenate of lead as it appears 

 in the markets. W, H. Volck, of Watsonville, Cal., * *has found that 

 the foliage of fruit trees of the Pajaro Valley, which opens to the 

 ocean and because of the atmospheric conditions on this account 

 becomes covered early in the evening with dew which remains on 

 the foliage all night and often far into the day, because of the fogs 

 that prevail and continue at times for several weeks, that here the 

 foliage of apple trees is remarkable susceptible to such an extent as 

 to interefere with the effective control of the codling moth by these 

 sprays. It was found tliat different samples of arsenate of lead, when 

 dissolved in natural water and when apj>lied at the same time under 

 similar conditions of dew and fog and the same kind of foliage, did 

 no harm, whereas in the case of other samples the effects varied 

 from from slight injury to well nigh entire defoliation. These 

 effects indicate a radical difference in the chemical properties of 



••Science, June 2nd, 1911, Vol. 33, Page 866. 



