32 



FARMERS BULLETIN 843. 



to find seedling nursery stock covered with galls, but budded or grafted 

 pecan trees growing adjacent may, and usually do, escape injury. 



Certain pecan trees in orchards are exceptionally subject to attacks 

 by this insect, while trees growing immediately adjacent to the affected 

 ones are not attacked and mature their full crop of nuts. Judging 

 from the past behavior of the hickory phylloxera, it does not appear 

 that this insect will be a very serious drawback to commercial pro- 

 duction of improved varieties of the pecan under orchard conditions. 

 This aphid attacks certain species of hickory as well as the pecan. 



CONTROL MEASURES. 



Under ordinary circumstances pecan trees slightly infested by this 

 insect will hardly demand special remedial measures. Like many 

 other insects, this species is subject to great fluc- 

 tuation in numbers, and the amount of damage 

 therefore will vary considerably from year to 

 year. This variation in abundance is due to the 

 fact that the insect is held more or less com- 

 pletely in check by natural enemies. 



So far as present knowledge of this insect goes, 

 no very satisfactory method of control can be 

 employed during the growing season on trees that 

 are so badly affected that the nut crop is seri- 

 ously interfered with. It has been recommended 

 that as many as possible of the badly affected 

 leaves and shoots be clipped off by means of a 

 12-foot pruner before the galls open, and then 

 burned immediately; but this treatment will 

 hardly prove feasible for large trees. Perhaps 

 the insect could be destroyed while in the egg 

 stage, during the dormant season, by spraying 

 with lime-sulphur solution, kerosene emulsion, 

 or miscible oil; but so far no actual work along this line has been 

 undertaken. 



If certain varieties of pecans show an exceptional susceptibility to 

 infestation year after year, top-working such trees with resistant 

 sorts doubtless would prove a practicable means of avoiding injury 

 by this species. 



THE LITTLE HICKORY APHID.i 



Often during the course of the season, especially in the spring and 

 autumn, pecan foliage is seen to be infested by a little lemon-yellow 

 aphid or plant-louse. This insect is commonly called the little 

 hickory aphid, because it was first discovered feeding upon the hickory 

 and- because of its small size. Besides feeding upon the hickory 



FIG. 38. The walnut cater- 

 pillar: Pupa. Somewhat 

 enlarged. 



Monellia caryella Fitch. 



