Honeydew 



leaves become covered by a sticky fluid called 

 honeydew, which is produced by aphides or scale 

 insects living upon the trees above them, and which 

 drops down, effectively closing aU the pores on their 

 leaves through which the various gases should pass, 

 and causing their suffocation or starvation. Lime 

 trees, while by no means the only ones, are particu- 

 larly troublesome cover for shady lawns because of 

 this. Any remedy beyond a frequent spraying 

 of the grass with water would be very difficult to 

 apply, and entail unreasonable expense. 



Honeydew often falla upon other plants from 

 aphides and their allies, and damages them in a 

 similar way, and also forms a medium for the growth 

 of a set of fungi called black moulds. These black 

 moulds are not directly destructive to the plant, are 

 wholly superficial, and may readily be rubbed o£E 

 the leaves or fruits on which they are found. They 

 are, however, very disfiguring, and worse still, they 

 obstruct the Ught so that the process of food-making 

 is seriously interfered with. The remedy is of course 

 to attack the insects which are the source of the 

 honeydew and to cleanse the plants by spraying or 

 sponging with water or soapy water. 



Soil acidity is a frequent cause of ill-health in 

 other plants than grasses. As has already been 

 pointed out, it is very liable to arise when drainage is^ 

 insufficient, but it also occurs in soils devoid of lime 

 and in soils to which organic manures have been 



26 



