CHRYSANTHEMUM MIDGE. 



15 



sidered. The control of the adult stage need not be taken up in experi- 

 mental manner, in view of the known fact that such fragile flies can 

 easily be controlled by light fumigation with hydrocyanic-acid gas or 

 by burning tobacco papers, provided it is done at the correct time. 

 The preceding paragraphs clearly point out the advisability of 

 determining the practical value of the several premises stated. 

 Incidentally such factors must necessarily be solved independently 

 of each other, but with the final view of either applying each separately 

 when the case so warrants or consolidating such phases as would be 

 most practical and consistent with commercial practices. The 

 practical conclusions and recommendations that follow were deduced 

 from results that are outlined and stated in the following pages. 



EXPERIMENT 1.— CONTROL OF EGGS BY MEANS OF DIPPING INFESTED CUTTINGS. 



Emphasis has been placed on the importance of beginning with 

 clean cuttings in the spring. It, therefore, was found advisable to 

 test out this point, and, if effective, such practices would be a safe- 

 guard to growers whose stock was badly infested as well as growers 

 who had received outside material. 



Three lots of six cuttings each were treated by J. L. Dietz as given 

 in the following table. After treatment they were planted in sand. 

 The tray, together with the plants, was then protected from further 

 attacks by placing it under a close-mesh screen. The plants were 

 treated September 26, and observations taken October 5 and 10 

 and November 1 are given in Table V. 



Table Y .—Control of eggs by means of dipping infested cuttings. 



Ex- 

 peri- 

 ment. 



Treatment. 



Observations and results. 



1 

 2 



3 



40 per cent nicotine sulphate (1-500); laundry 

 soap 1 ounce to 1 gallon; tips of cuttings 

 dipped. Sept. 26, 1918. 



Same treatment as above, except that entire 

 cuttings were dipped. Sept 26, 1918. 



Nov. 1: Eggs did not hatch; no new galls devel- 

 oped; 4 plants well rooted, 2 plants poorly 

 rooted. 



Nov. 1: Eggs did not hatch; no new galls devel- 

 oped, neither did original galls develop any 

 further; 4 plants well rooted, 2 plants poorly 

 rooted. 



Nov. 1: Eggs hatched; 1 plant had 3 well-devel- 

 oped galls present; 3 plants rotted off; 3 plants 

 were well rooted. 







DISCUSSION OF RESULTS. 



Comparing the results of both treated lots with those of the check, 

 the results are fairly conclusive. On the treated plants the eggs in 

 each case did not hatch, neither did the young galls originally present 

 make further progress, whereas, in the case of the check, while only 

 one plant showed definite results, it is clear that the galls developed. 



The effect of such treatment on the plants is somewhat inconclu- 

 sive due to the rotting off of three plants in the check. In the case 

 of the treated plants, four survived in each lot. 



