THE STRAWBERRY ROOT LOUSE IN TENNESSEE 1 
By S. Marcoyitch 
Entomologist , Agricultural Experiment Station of the University of Tennessee 
INTRODUCTION 
In Tennessee, strawberries are classed 
as nursery stock and before they can 
be shipped an inspection is required for 
injurious insects, particularly for the 
strawberry root louse ( Aphis forbesi 
Weed). Since no extended study of 
this insect in Tennessee had ever been 
made and since little is known con¬ 
cerning it in other States, except in 
Delaware, it seemed desirable to make 
a study of its habits and to determine 
if possible its economic importance. 
When one considers the vast quanti¬ 
ties of strawberries grown in Tennessee, 
which is the largest strawberry-produc¬ 
ing State in the Union, and the time 
consumed each year inspecting them, 
the need of a more definite knowledge 
of the economic importance of this in¬ 
sect becomes apparent. 
GEOGRAPHIC RANGE 
The strawberry root louse is a native 
insect confined to eastern North 
America, and has been reported in¬ 
jurious in Illinois, Ohio, Maryland, 
Tennessee, and Delaware, although it 
has recently been learned through 
correspondence that it is no longer so 
considered in the last-named State. 
In Tennessee it is present wherever 
strawberries are grown. 
HOST PLANTS 
The cultivated strawberry, Frag aria 
sp. appears to be the only host of 
Aphis forbesi Weed. Repeated efforts 
have been made to find it on other 
plants, but without success. Often 
the roots of various weeds are infested 
with lice very similar in appearance to 
the strawberry root louse, but close 
examination reveals them to be other 
species, usually the corn root louse, 
Aphis maidiradicis. 
ECONOMIC IMPORTANCE 
Plant lice in general are of great 
economic importance, yet there are 
many species that do little or no harm. 
To obtain exact data in regard to 
injury caused by Aphis forbesi Weed, 
experiments were conducted in the 
field during 1921 and 1922. The vigor 
of a strawberry plant is indicated by 
the number of plants and runners 
which it produces. Plants artificially 
infested with lice were set out in March 
and a record was kept of the number 
of plants and runners produced. The 
plants used in the control plat were 
freed from any lice that may have 
been present by dipping them in a 
tobacco solution. The control plat 
was also frequently sprayed with to¬ 
bacco to guard against infestation. 
The results obtained for the year 1922 
are as follows: Of 12 infested mother 
plants the maximum number of plants 
produced by any one was 150, the 
minimum 12, and the average 47.6. 
Of 22 control mother plants the in¬ 
dividual maximum was 120, the mini¬ 
mum 4, and the average 49.7 plants. 
The mother plants were set March 28 
and the count of plants produced was 
made September 16, 1922. The dif¬ 
ference in the percentage of plants 
produced by the infested mother plants 
and the controls was small, and could 
easily come within the limits of ex¬ 
perimental error. 
Practically the same results were ob¬ 
tained in 1921. Ladybird beetles often 
destroyed the lice on the crown of the 
plant, where they are frequently found. 
In such cases the plants were artificially 
reinfested. 
To ascertain the general importance 
of the strawberry root louse a circular 
letter was sent to all the important 
strawberry-producing States. Replies 
from Iowa, Illinois, Ohio, New Jersey, 
Delaware, North Carolina, Georgia, 
Florida, Louisiana, Mississippi, and 
Arkansas indicated that the strawberry 
root louse was not considered injurious 
to the strawberry, or that little con¬ 
sideration was given to it. The only 
State reporting serious injury from this 
pest was Maryland, where it is con¬ 
sidered “highly undesirable” in the 
light sandy soils, although no data were 
given. The strawberry soils of Ten- 
i Received for publication June 11, 1924, issued, May, 1925. 
Journal of Agricultural Research, 
Washington, D. C. 
( 441 ) 
Vol. XXX, No. 5 
Mar. 1, 1925 
Key No. Tenn.-3 
