f>2 \ \ N UAL BBFOftTS ok ok l\\ K I M i: NT OF aokk T LTURE, iy4U 
Extensive t f>t >. in several localities, of inbred and hybrid liel< I and 
sweet corn- for resistance i<> tin* com earworm showed wide differences 
in the degree oi infestation. In some <>f these bests a method of arti- 
ficial infestation wan used t<> insure significant results. This work 
gives some promise that reduction of injury by the earworm may l>e 
accomplished through the eventual commercial use of resistant -trains 
of corn. 
Ii was discovered that the corn flea beetle, the principal vector of 
Stewart's disease of corn, may become a carrier <>i" this disease through 
early spring feeding on wild grasses in which the disease has appar- 
ently survived the winter without showing external symptoms. The 
beetles may thus become infective to young corn on which they subse- 
quently feed, even though they have not carried the bacteria causing 
the disease inside their bodies through the winter. During the year 
the larvae of this flea beetle were found to feed on barnyard grass, 
fall panicum, yellow bristle grass, and a sedge, in addition to other 
hosts previously determined. 
The European corn borer became more abundant in 1 1 id i ana. whereas 
marked decreases were observed in Connecticut and New Jersey. 
Borer populations in general averaged less than LOO per LOO corn 
plants in the areas surveyed, but in spite of lower populations in the 
Eastern States they averaged over 500 borers per 100 plants in some 
part- of Massachusetts. Connecticut, and Rhode Island. Some fields 
in Xew ,Jei-se\ contained concentrations up to 40 borers per plant. 
During \ { XY.) the pest was found for the first time ill extreme north- 
eastern North Carolina and extreme northeastern Illinois. 
In an investigation of the nutritional requirements of the European 
corn borer, feeding tests with corn-leaf and internode tissue indicated 
that survival and weights of corn-borer larvae are affected by differ- 
ences in the percentage- of moisture, sucrose, reducing sugars, and 
protein contents in their food: but chemical differences of this kind 
between resistant and susceptible corns appeared to be insufficient to 
account for the borer's behavior while feeding on them. Differences 
observed in average weights of larvae nourished on tissues of resistant 
-train R4XHy and the susceptible strain AxTr, when both were 
manipulated to produce high sugar concentrations in them, indicated 
that factors possibly of a physical character in the tissues of R4XHy 
interfered with Larva] feeding, <»r possibly that defective digestion 
or assimilation was caused by such characters of the corn tissues. 
The pi I readings of the blood of the Larvae varied with those of its host 
plants. 
The isolation and breeding of pedigreed Lines of t ho European com 
borer definitely indicated that those having a single generation a year 
are genetically distinct from those having two <>r more generations. 
Studies of held collected material, however, showed that the multiple- 
generation st ra in now occurs quite generally in the Lake States as w ell 
as in the Eastern States. Therefore, since there no Longer appears to 
be any object in maintaining quarantines against it in this area, even 
though it i>> a distinct strain, the study has Seen concluded. 
In 5 years of study, i < - ,;, »"» to L939, inclusive, <d' sweet corn resistant 
t" borer al tack near Toledo. ( )hio, 690 entries, comprising I'd Bantam, 
L34 Country Gentleman, and L05 Evergreen Lines were tested in three- 
fold replication by the random block method. Among strains carried 
