98 
Alfalfa aphid in Oregon on alfalfa, votch, and Austrian winter 
field peas.--L. P. Rockwood, Forest Grove, Oreg., reports that the 
population of Illinoia pisi Kelt. on alfalfa vradually increused dur- 
ing October but declined early in November. This decline coincided 
with the progressive defoliation of alfalfa by fumgous disease and 
frost, which was nearly complete by November 10. ‘This is a condition 
that normally occurs every fall in the Willanette Valley. Sexual 
forms of Illinvia pisi appeared on alfalfa-early in October and con- 
tinued throughout the month. Alate viviparous females were produced 
very sparingly on alfalfa during October and early in November. The 
disease produced by the fungus Empuse aphidis Hoffman. was prevalent 
auong the aphids on alfalfa late in October and carly in November, 
and aphids parasitized by the internal hymenopterous purasites 
Aphidius anc Praon were: common as late as October k6. Our obdserva—_ 
tions. on I. pisi on volunteer.and planted legumes, including vetch 
and Austrian peas, iti various parts of the Willenette Valley confirm 
our conclusions that volunteer and.early fall-sowm annual legumes 
furnish foci for early fall establishments cf large aphid populations. 
These concentraticns produce al 
after they have ceased to come from alfalfa and Scotena brocm, and, when 
the winter is mila, alates in the spring are y»roduced on these annual 
legumes from viviparous forms earlier than on alfalfa und broom from 
eggs. This year it soems that annual leyuues seeded avout Octover 20, 
or later, at a distance from any infested host »lants, will remain 
free of I. pisi until the spring migrations. Our experience with 
plots indicates that this cannot be demonstrated by nlots unless a 
large area for wide Separation of the plots from other lezumes could 
be made available. 
te viviparous females in numbers long 
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Increase of alfalfa aphid in October in Nevada.--S. J. Snow, 
Salt Lake City, Utah, reports that Illinoia »isi occurred in greater 
numbers on the third crop of alfalfa in Octover than in any other 
month of the year, although it was too scarce to be wf any importance, 
The estimates were obtuined by sweeping varivus fields in which cut- 
ting had been delayed. The catch from a. total of 6,150 sweepe through= 
out the month, and to sume extent on frosted alfelfa, gave an average 
of 42 aphids per 25 sweeps.. This great incréase over a catch of 5/8 
aphids in September and 1.7 in August is lergely due to the fact that 
two fields became heavily infestec, comparatively, in the middle of 
October. The cutting of the crop soon thereafter, however, and the 
heavy frosts quickly reduced this potentially injurious »orulation. 
Wingea forms were late in apdearing anc remained séarce in October 
and the early part of November. -They increased from 0.3 yercent in 
September to 3 percent in October. Im the inscctary, on the other 
hand, they increased rapidly curing this »erivd and gre 
numbered the wingless forms. . On warm days they were clu 
hundreds on the screen sides uf the insectary. 
a eran oe 
