APHIDS INJURIOUS TO ORCHARD FRUITS. 35 



Two principal 2:)laiis of attack may be followed in the control of 

 orchard aphids. Those species which winter in the egg stage on the 

 plants to be i^rotected may be treated Avith sprays early in the spring 

 as the buds are expanding, to destroy the young stem-mothers. 

 Treatment at this time assumes that without it the aphids would 

 become injurious later in the season and is in the nature of insurance. 



Following the other plan, spraying is not done until the insects 

 actually have become troublesome, which does not occur as a rule 

 until several weeks after the foliage has put out. With species that 

 cause the leaves to curl this is too late to obtain much benefit from 

 spraying. In view of the more or less scattered 'occurrence of aphids 

 many growers will prefer to delay treatment until the insects actually 

 are present on the plants in destructive numbers, and in the case of 

 those species which do not curl the leaves to any extent this plan will 



Fig. 27. — The adult syrphid fly Allograpta obliqua. Much enlarged. (Davis.) 



be satisfactory. It is a question for the grower to decide whether 

 under his conditions danger of aphid injury, especially by the leaf- 

 curling species, makes the bud application desirable or whether this 

 danger is so small that he is warranted in taking chances on the 

 insects becoming troublesome. Examinations of the plants to deter- 

 mine the abundance of winter eggs and young stem-mothers on the 

 opening buds should be of assistance in this connection. 



SPRAY FORMULAS. 



COMMERCIAL NICOTINE SOLUTIONS. 



Aphids are killed by surprisingly small quantities of nicotine in 

 water, and because of the entire safety with which it may be applied 

 to plants nicotine is better suited than other sprays to control these 

 insects. While the cost of the concentrated article is high, the ex- 



