102 PLANT DISEASES 



names already given. For the present purpose, however, 

 this is unimportant, as it is the insects that have to be 

 dealt with directly, and not the fungi. 



PREVENTIVE MEANS. Swingle and Webber have 

 demonstrated that ' resin-wash ' is effective, inasmuch as 

 it destroys the 'honey-dew' secreting insects. Spraying 

 should be done when the insect is in the larval or pupal 

 stage ; and it is important that the under surface of the 

 leaves be thoroughly wetted. Webber has observed that 

 members of a genus of fungi called Aschersonia are 

 parasitic on the insects forming * honey-dew,' and are 

 often present in immense numbers ; and sees in the 

 introduction and fostering of these parasites a means of 

 keeping the insects in check. The fungi appear under 

 the form of small yellowish or orange pustules on the 

 leaves, and such should be looked upon as friends wher- 

 ever observed. I have shown that species of Aschersania 

 which hitherto were only known to produce a conidial 

 form of reproduction on living leaves produce an asci- 

 gerous form of fruit, following the conidial stage, on fallen, 

 dead leaves; consequently such dead leaves should be 

 allowed to remain to produce the ascigerous fruit, and 

 thus further aid in the multiplication of the fungus. 

 Fumigation with hydrocyanic acid gas is also very effec- 

 tive ; treatment to last about forty-five minutes. Should 

 be done when the temperature is low. 



Swingle and Webber, U.S. Dept., Agric. Dept. Veg. and 

 PhysioL, Bull. No. 8. 



Webber, I.e., Bull. No. 13. 



Massee, Journ. Bot., vol. vi. p. 357, pi., for description 

 of ascigerous stage of Aschersonia. 



