828 PLUBi. 



by the Plum Aphis — the Aphis jmini — never having the 

 \iiYp,e frontal tubercles (figured, much magnified, at p. 119) 

 which are characteristic, together with the lowest joint of the 

 horns being gibbous or toothed, of the Hop Aphis, — the 

 Phorodon humuli. The difference in size of these very 

 minute insects is indistinguishable by the naked eye. 



Prevention and Piemedies. — Washes with a foundation of 

 soft-soap are the most desirable, because they have the great 

 advantage of sticking in some degree to the Aphides. When 

 these insects (as before noted) are covered with a kind of 

 mealy powder, many of the washes used simply run off them 

 at once ; and unless the application sticks to them, so as to kill 

 them, or is given so violently as to knock them from their 

 position, the labour does little good. 



Washes or regular " swilliugs "-down, applied as in the 

 Hop-grounds by means of a large garden-engine fitted with a 

 gutta-percha tube and jet, or rose, or spray-syringe, so as to 

 send the mixture under the leaves, as well as over and round 

 the whole of the tree, and thus drench it down completely, do 

 good in many ways. They knock many of the Aphides off, 

 they cleanse the leaves of the accumulating dirt . which is 

 choking them, and also make the surface distasteful to the 

 plant-lice for a while ; something might be done in the 

 autumn or winter or early spring to lessen impending attack 

 of the next season by destroying the eggs on the Plum-stems 

 or branches. 



Some kinds of Aphides hybernate, and of some we cannot 

 be sure whether they do so or not; but in the case of the jlphis 

 pruni I am not aware of there being any record of the Aphis 

 living through the winter, and we know (as mentioned, p. 327) 

 that the eggs are ready for laying in November. 



Washings and syringings with soft-soap mixtures, with 

 anything mixed with them that would coat the egg and 

 poison the embryo, or poison the young Aphis when it 

 hatched in spring, would be very serviceable. This course is 

 recommended in German orchard treatment ; and for these 

 purposes, that is, to destroy Aphis eggs, or Aphides harbour- 

 ing on the trunk or branches, the soft-soap and mineral-oil 

 emulsions, and washes mentioned in Index and also under 

 the heading of "Winter Moth," would be serviceable. 



Where there is plentiful water supply at hand, and also 

 means of throwing it with force, I have known much benefit 

 come from sending even this, with no additions, strongly 

 at the stems and branches ; fairly " swilling " the tree down. 

 Whether the quantity of water thus running down to the 

 roots would be injurious in late autumn or winter would be a 



