Aphids or Plant-lice 



NATURE OF INJURY 



The indications of aphid infestation are varied, the different plant- 

 lice affecting their hosts differently. A slow growth associated with 

 wilting of the leaves, which are apt to be a pale yellowish green, is char- 

 acteristic of root-louse attack. 



Most lice which feed above ground prefer the new, soft growth of 

 plants. If the leaves and new growth wilt, if the leaves are covered with 

 a sticky, sweetish substance called "honey dew," or if they become curled 

 and distorted, plant-lice are very likely present. 



Ants are very fond of honey dew and in order to secure it are known 

 to care for aphids and their eggs, exhibiting in this an instinct which 

 amounts almost to reasoning. Ants and aphids are so closely associated 

 that the presence of the former on a plant is a very good indication that 

 the latter are present also. 



METHODS OF CONTROL 



The stomach poisons used in the control of biting insects 

 will not kill plant-lice. Contact poisons must be used. Even 

 then, the control of those aphids which live within galls or curled leaves 

 is very difficult unless the remedy is applied during the season when the 

 lice are in the egg stage or just as the eggs begin to hatch in the spring. 

 After these lice once become inclosed within the galls or leaves it is impos- 

 sible to reach them with any contact spray. Several species are so cov- 

 ered with a flocculent secretion that a spray must be very thoroughly 

 applied and with considerable force to be effective. 



Kerosene Emulsion 



Where only a few plants in the garden or a small number of orna- 

 mental shrubs are to be treated, kerosene emulsion has long been a stand- 

 ard remedy because of its simplicity and the fact that all the ingredients 

 required in its making are always at hand. 



This contact poison is usually made in the form of a stock solution, 

 in which form it can be kept for several weeks. When used it is diluted 

 by adding water. The s,tock solution is made as follows: 



Mix one-half pound of common laundry soap or whale oil soap in 

 one gallon of water by boiling over a slow fire until the soap is completely 

 dissolved. After removing from the fire add two gallons of kerosene and 

 beat until the oil is thoroughly mixed with the soap and water. 



This stock solution is too strong for any plant and will kill the leaves 

 and tender parts if applied to them. Before using thoroughly mix one 

 part of the stock solution with ten to fifteen parts of water. Apply a 

 little to the plants to be treated and watch the results. If the leaves 

 are burned dilute the solution still more. 



Black Leaf 40 



This js a tobacco preparation containing 40 per cent nicotine, or the 

 active poison in tobacco. As a remedy for plant-lice one part of "black 

 leaf 40" is mixed with 600 to 800 parts of water and sprayed on the in- 

 fested plants, care being taken to spray the aphids thoroughly. As the 

 black leaf is very poisonous great care should be taken in handling it. 



114 



