INJURIOUS INSECTS, FUNGOUS DISEASES, ETC. 181 



twigs and increase in size until midsummer, or a little later. 

 Then the males mature, and the females, after impregna- 

 tion, lay their eggs, which fill the space beneath the scale. 

 Sometimes there are two broods during the season. 



There is only one period during which this insect can be 

 satisfactorily reached; that is, when the eggs have hatched 

 and while the larvae are moving about or have just set. 

 This is during late May or early June. As soon as the 

 larvae are observed, spray with whale-oil soap at the rate of 

 one pound to five gallons of water, or kerosene emulsion. 

 Repeat, if possible, a week later to reach delayed larvae. 



Plant Lice. — Most shade-trees suffer from plant lice to 

 a greater or less extent; but none more than the Norway 

 maple. These insects multiply very rapidly, suck the juices 

 of the leaves and shoots, and so exhaust their vitality. 

 When the insects become abundant the honey dew excreted 

 by them sometimes covers the leaves with a sticky secretion 

 that may be abundant enough to drop to the street below. 

 This secretion tends to clog the foliage so that it may drop 

 while yet perfectly green, and a black soot fungus is also 

 likely to develop. 



Plant lice are most abundant during a cold, wet spring, 

 and the attack usually does not continue after the first spell 

 of hot dry weather; so that treatment is generally not 

 found necessary. 



Should spraying be desirable nothing is better against 

 plant lice than whale-oil soap at the rate of one pound to 

 five gallons of water. 



BORERS 



Besides the leaf-eating and the sucking insects that in- 

 jure trees through defoliation, shade-trees are also subject 

 to the attacks of borers that feed on their wood tissue. As 



