Vol. 16—1962 - NorthEastern Weed Science Society

301
In the SUIIIIIlf)1' seeding, the highest"yields ot alfali'a were obtained trom.
the low rates of neburon and dacthal with the dr.vmatter production comparable
tor each chemical. While not si~ lower, somewhat lower yields were
obtained trail ~,lllb.; dact~a SIb.; diphenaJll.i;d, .3lb.; DNBP,It ,
lbo; and 2,4-IJl plus dalapon. Yiaa;dS wre ~ign1f'ic~ loiter, however, wh~
G34696was uaEid..DOubUn$ the rate'ot 'diphenamid or D" resulted in a '
hi~ signif'icant yield reductionotthe alfalfa. Serious injury' trom both
rates was obtained from. tritluralin and diuron o
Control ot the predominant weed, old w:l.tchgrass,isindicated by the
estimate ot stand given in Table 1. Oomplete grassoomrol was obtained tl'd!ll.
both rates ot diphenamid and diuron and trom. the high rate ot tritluralin,
with CQrlplete selectivity obtained onl,y with the diphenamid.. Alfalfa was
serioual;r injurec:1 by diuron and tritluralin as stated pt'eViously 0 While not
cOJllPlete, good' grass oontrol was obtained trom. both rates ot neburon,
dacthal, the 2,4-l1B anddalapon OCIIIIb1natiODS, and the low rate ot tritluralin.
Only tair control was obtained from DNBPand G34696.
DiscussiG£1
Diphenamid was outstanding" in its degree ot selectivity on alfalfa in
both spring and summer seedings ~ gi 'rlng ne8.1·~ complete weed control without
injury to alfalfa at the .3 lb. per acre rate. This material merits further
testing on alfalfa as a hi~ selective, wide spectrum pre-energence
herbicide 0
In-the summer seeding reported, neburon and dacthal were quite effective;
however, these IIIll.terials have not generally cot.trolled as wide a range of
weed species.
Two JJmitations ot l1mP tor weed oontrol in altalta are shown in this
experilnent. The nat"l'OWrange ot alfalfa tolerance is shown by over a '$if,
reduction in alfalfa yield as the DNBPis doubled from. 3/4 to li lb. per
acre. The weakness 01' DNBPin post-emergence control ot grassy weeds is
shown by the poor rating at eithe!" rate compared, e.g., with dj,phenamido
G34696merits turther testing on alfalf'a, at rates ot 1 lb. per acre or
less. While it did not give complete old witchgrass oontrol in this experiment,
in a separate trial at the storrs station this mat.erial controlled a
tair~ wide range at weed species. The dalapon plus 2,4--DB combination
caused tempor8.17 injury to the alfalfa as evidenced by leaf curling and
stunting. Injury
spring seed1ngs.
has been more frequent at storrs on summer seadings than
The injury noted wu outgrown, however, by tJle time of
an
harvest.
Tritluralin shows no promise tor alfalfa weed control because ot severe
injury. The injury pattern is unique in that emergence occurs but development
beyond the cotyledonary stage does not occur on most plsnt80 If' further
d3V810pnent does event~ occur, multiple shoots torm trom the coty.ledonary
"--'" nodes resulting in multiple small steme.