THE MONTHLY BULLETIN. 441 



THE WOOLLY APHIS AS A PEAR PEST * 



By Geo. P. Weldon. 



From an economic standpoint the woolly aphis {Eriosoma lanigera) 

 has been associated almost entirely with the apple, its range of distri- 

 bution being practically as wide as that of its host. Quite an extensive 

 correspondence with many of the leading entomologists of this country 

 -^scme who have been particularly interested in a study of this pest 

 as well as other aphids — and a study of the literature regarding it. 

 justify the statement that few entomologists have ever found it plenti- 

 ful on pear trees, if at all, and outside of the states of Oregon and Cali- 

 fornia it has been practically unknown on the roots of the pear. 



The writer's attention was first directed toward the possible serious- 

 ness of this insect upon the pear, at ]Martinez, California, August 5. 

 1913. At this time it was found in abundance on the roots of seedling 

 trees in the nursery row, as well as on old trees of the Bartlett variety, 

 nearby. Previous to this time records of the occurrence of woolly aphis 

 in pear orchards of the Sacramento River Valley had been made and 

 some experimental work had been done in an effort to control it. 



Since the time of the first observations by the writer an attempt has 

 been made to determine the prevalence and distribution of this pest 

 throughout the State, and it is now known that there are few places 

 where it does not occur, and in some of the mountain districts at least, 

 its presence has resulted in quite severe injury to trees. The following 

 counties are laiown to have infested orchards : Lake, Mendocino, 

 Sonoma, Napa, Yolo. Contra Costa, Santa Clara, Sacramento, Sutter, 

 Nevada, Placer and El Dorado. 



EFFECT UPON THE TREES. 



Some of the worst infested trees seen were in orchards from one to 

 three years of age. The first case of badly infested young orchard trees 

 was observed in Lake County on August 22, 1913. The trees, which 

 were of the Bartlett variety, were set during the spring of 1912. In 

 walking through the orchard it was noticed that several of the trees 

 were sickly. They had made scarcely any growth, the foliage was 

 yellowish and very sparse. The soil was removed as well as possible 

 from about the roots, and it was found that the smaller fibrous roots 

 were covered with aphis in such abundance that the sickly condition 

 of the trees could readily be accounted for by its presence. Other trees 

 in this same orchard with normal growth and foliage did not have a 

 bad infestation. These trees were planted in new soil, so that there was 

 no way of accounting for the presence of the pest, except through 

 infestation of nursery stock. Thus the treatment of nursery stock may 

 have an exceedingly important bearing upon the problem in the 

 orchard. On the same date when the young trees were inspected, two 

 old orchards — at least 20 years of age — were also carefully inspected, 

 and such an abundance of the aphids was found that there could be 

 little doubt that they were a serious pest. The characteristic appear- 



*Paper read at meeting of American Association of Economic Entomologists, at 

 Berkeley, California, August 9, 1915. 



