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^TRY H.O 
Vol. L1X. No. 2629. 
NEW YORK, JUNE 16, 1900. 
*1 PER YEAR. 
THE DESTRUCTIVE GREEN PEA LOUSE. 
NEW DEVELOPMENT OF A LITTLE-KNOWN IN8KCT. 
Crimson Clover and the Pea Crop. 
PEAS FOR THE CANNERY.—An important agri¬ 
cultural industry in many sections of Delaware, 
Maryland and New Jersey, is the growing of green 
peas for the cannery. Figures are not available for 
the other States, but in southern Delaware about 
150,000 cases of two dozen cans each, representing 
over 2,000 acres of peas, are packed each year. At 
Seaford, Del., is located the factory of Greenabaum 
Brothers, Which is one of the largest in the country, 
with a capacity of 125,000 cans per day, and other 
large factories are located at Bridgeville and Milford. 
Heretofore, the pea crop has been a profitable one 
both to the grower and canner. When it is consid¬ 
ered that the peas are usually followed by tomatoes 
or corn, an average of about $25 per acre is not un¬ 
profitable, while the most successful growers not in¬ 
frequently clear from $50 to over $100 per acre. For 
the canner the early and late peas form a succes¬ 
sion, maturing from the first to the last of June or 
early July, their season closing just in time to per¬ 
mit dhange of machinery and preparation for hand¬ 
ling sweet corn. During the season of 1899, however, 
a serious blow was given this usually profitable in¬ 
dustry by the appearance of plant lice upon the peas 
in such countless numbers as to cause practically 
an entire loss of the late crop, and from one-half to 
two-thirds of the usual yield of the earlier sorts. As 
a pea pest the insect was entirely unknown, and upon 
examination it proved to be a new species, being 
different from any previously described plant lice. 
A WIDESPREAD PEST.—The almost simultaneous 
appearance of this new species throughout the At¬ 
lantic coast plain, from North Carolina to the Bay 
of Fun'dy, Was a most unusual phenomenon. But 
few records were made of it west of the Alleghanies, 
though found as far west as Toledo, Ohio, and the 
worst injury was done in the belt formed by Vir¬ 
ginia, Maryland, Delaware, and New Jersey. This 
year it is doing serious injury in these four States, 
and has recently been reported from Queens County, 
New York. In general appearance the Pea lice are 
much like the common green fly of greenhouses, or 
the Wheat aphis, but are much larger than either of 
these, and are entirely of a light pea-green color, ex¬ 
cept the reddish eyes. Both winged and wingless 
forms occur, the winged forms becoming more com¬ 
mon as the food plant becomes overcrowded. Both of 
these forms reproduce live young parthenogenetic- 
ally, as is common among plant lice during the Sum¬ 
mer season, the wingless forms reproducing more 
rapidly than the winged. Prof. W. G. Johnson has 
recently published some very interesting observations 
upon the rate of reproduction. He says: ‘‘As an ex¬ 
ample, a young one, born March 4, reached maturity 
(winged form) March 16, or 12 days from the time 
of birth, and was reproducing living young March 19. 
From March 19 to April 11, she became mother of 111 
young, and died on the latter date. Her first young 
WINGLESS FEMALE LOUSE AND YOUNG. Fig. 126. 
(wingless form), born March 19 were producing on 
March 31, or 11 uays from time of birth. From 
March 31 to April 11 she gave birth to 120 young, 
and died.” As yei no true males, or females, or eggs 
of this species have been found, though from our 
knowledge of nearly-related species we surmise that 
they will ultimately be found as cold weather ap¬ 
proaches upon the Winter food plant. 
TOO-HOSPITABLE CRIMSON CLOVER—In 1899 
the lice first appeared in noticeable numbers about 
the time the early peas were in blossom, and were 
quickly Observed, as they prefer to cluster between 
the unfolding leaves of the terminals, and on the 
blossoms and forming pOds. Owing to their rapid 
manner of reproduction the vines had already be¬ 
come crowded with the lice by the time they were 
observed, and as nothing was Known of the species, 
and there seemed to be no known way of combating 
it, much of the early and almost tne entire late crop 
was lost. With the cutting of the pea crop the lice 
were not noticed further, except here and there in 
garden patches, where they might be found until 
EGGS OF LACE-WINGED FLY WITH WINGLESS PEA LICE. 
Fig. 127. 
late in November. The question most naturally 
arose, ‘‘Where were these lice—heretofore unknown 
—before they appeared on the peas in the Spring, 
or, in other words, where and in what state do they 
pass the Winter?” The answer was foun'd late in 
April of the present year by the discovery that in 
Virginia, Maryland, and Delaware the Crimson clover 
was badly infested with this very species. As the 
clover approached maturity, the winged lice flew from 
it to the adjoining peas, or, in some instances, were 
carried a considerable distance by the wind. In talk¬ 
ing with several careful observers we have found that 
what was in all probability the same species of 
aphid has been noticed on Crimson clover for at 
least six or seven years, and in one instance in such 
large numbers as to threaten the life of the crop. 
Though no positive identification can now be made it 
seems highly probable that it was the same species, 
as it i's much larger in size than most plant lice, and 
we have not observed nor seen any record of any 
other species occurring in large numbers on Crim 
son clover. With the turning under and cutting of 
the Crimson clover the lice are to be found quite 
common upc'i Red clover, upon which they probably 
LACE-WINGED FLY SIDE VIEW. Fiu. 128. 
live after the peas are cut, and until the young clover 
appears in the Fall. It seems almost certain, there¬ 
fore, that the insect is, first of all, a clover pest, and 
very prolbable that originally it was a peSt of Crim¬ 
son clover. In general, the lice appeared on peas 
later this season, and in smaller numbers. In Mary¬ 
land, some of the early crop will be seriously dam¬ 
aged. In Delaware, not over 30 miles distant, hardly 
a louse has been found upon the early peas, and a 
fine crop is being canned. Why this difference is a 
decided mystery. 
ROWS OR BROADCAST SOWING—It was most 
interesting to Observe the immunity of the early peas 
—mostly Alaska—'when growing immediately adjoin¬ 
ing a badly-infested piece of Crimson clover, while 
the late peas were becoming badly infested. Almost 
entirely in southern Delaware the peas are grown in 
rows from 20 to 30 inches apart, allowing cultiva¬ 
tion. Here and there, however, are found fields sown 
broadcast, or in eight-inch drills. Even early peas 
have been found badly infested when thus planted, 
and such fields have generally been attacked worse 
than those in rows. Inasmuch as there seems to be 
no method of combating the Pea louse, except when 
peas are in rows, it would seem that drilling or 
broadcasting must needs be abandoned, as, possibly, 
it should be anyway. Of the medium peas, the va¬ 
rieties Blue Beauty and Admiral are well infested 
with lice, each terminal containing a small cluster of 
old ones and their progeny. The French Canners are 
in some instances comparatively free from lice, while 
sometimes badly infested. The two former varieties 
have the pods already well formed, and though they 
will need thorough brushing, if injury to the crop is 
to be prevented, they probably will not be so serious¬ 
ly injured as the later varieties. The prospect for 
the late crop of Advancer and Horsford’s Market 
Garden is, however, much more discouraging. These 
are just in blossom, and covering blossoms and young 
pods are such masses of green lice as almost certainly 
to prevent the formation of peas unless they can be 
soon destroyed. The wet, cold weather of the pres¬ 
ent season has thus far greatly retarded the usual 
rapid development of the plant lice. Though the 
damp weather has also furnished the most favorable 
conditions for the development of the fungous dis- 
SYRPHUS LARVA EATING LICE. Flo. 129 
