Vol. 15—1961 - NorthEastern Weed Science Society

251.
TABLE3. EFFECTSOF APPLICATIONS OF HERBICIDES ONMANSFIELD
81RDSFOOTREFOiL'GROWNFORSEED.
Pounds Pounds Pounds Flowers Pods Umbles
Active In- c leen Oven-Dry Per Per Per
Herbicide gredient/A Seed/A Forage/A Urnbleff: Umble:!F Stem
,Datapon I 2.35 184.28** 2833** 4.01 12.99 14.57
4-(2.4-0B) 0.5 ,93.08*· 3005*· 5.36 7.57 7.69
Delapon & I 2.35 56.77** 2600*· 5.&:) 7.15 7.96
4-(2.4-DB) 0.5
Check 36e.73** 3503·· 2.52 15.05 12.43
--------------------_._---~--------------------------- - - -- - - - - - - - -
~pplication date May 13. 1960 **Significant at the 1% level
Harvest date July 16. 1960 =!tot analyzed statistically
stem counts June 22, 1960 Butyrac 118 '
The 1960tests were conducted in another area of the field described
immediately above. The experiment was designed as a randomized block with
5 replications of herbicides as main treatments and insecticides 8S aubtreatments
In strips across the blocks. This'design is reported by
Leonard and Clark (2) and is particularly adaptable to applying pesticides
in long strips across other plots. Rates and dates of application of
materials are given in Table 3. Sampling was essentially that as reported
above with the reduction of the SUb-samples from 5 to 3.
RESULTSANDDISCUSSION
Vermont studies in 1958 (3) and subsequent data 3 indicate that frefoi I
yields are substantially increased through the use of insecticides. Usually
such applications are made in the spring. Applying an herbicide with the
insect.ic;~de at, this same time would seem an economic procedure. Such econom,l:c;s~~
Id, however. be offset by any reducti on of seed yi e Id resu Iti ng
fr.9O\ detrimental herbicidal effects. Increases in the final yield 01 clean
seed resulting from the use of an herbicide to control unwanted planfs
would on the other hand seem to offer an economic practice of merit.
The data gathered in 1957 (Table I) and in 1959 (Table 2) would seem
to support this 'latter assumption. but subsequent findings are possibly
contradictive. The 1957 tests were conducted on & fairly old stand of
Empire trefol I which was moderately to heavily infested wlt~ weeds and
weed grasses. ,The use of dalapon appeared to be beneficial in the field
as fairly good grass 'suppression was achieved. This Is supported by the
data in Tab Ie I, but no differences were stat ist Ica I'y s igriif Icant due to
considerable fluctuation in yields as influenced by variebleresulfs from
the separate insectici.de applications, several of which have been excluded
from the table. Had these been excluded from the experimental design, both
dalapon and the dalapon-insecticide combinations would most likely, have
been stat ist icall y si gnif icant. ConsIderab Ie dandel ion infestatton In the
3MacCo l lom, G. B., vt. Ag. Exp. Sta. unpublished data.