Vol. 16—1962 - NorthEastern Weed Science Society

468
First, soil treatment within a few weeks prior to seeding grasses was more
risky than application to young, established grasse •• Injury was greater when
treating the soils and seeding~.~ later than when seeding and treating
:am-.u. later. ,. -
Second, four-week old turfwas'more toleram; of,.chemical treatment, in
general, .than wastwo-week old 'turf.. This trend dMLnot continue through the
9th week. ,For some reason the~~ui:tant injury wal,-greater, in general, on
the turf treated 9 weeks after,s!ted~ng than on yQlll)le%'turf. One possible explanation
,would be the weather condItions on or following the treatment d~te.
The growing conditions on August ~O\:h were consid.$ly less favorable than, on
July 12 or 28. The fescue and, ~oa lesser extent,i!the bentgrass wereno~
growing as rapidly, or exhibitiil,9 a.Shealthy an aPJ)Ul'ance in late August as
they did during July. It would appear that gr,pwin9'~onditions at the time of
treatment, as well as age of the young plant, are important considerations in
timing herbicide applications. .' .
Third, although chemical tr.a~nt often thin~ or delayed the initial
stand of g1'88S, ePloughplants ofteo'remained in hea!thy condition to eventually
give satisfactory stands of turf. -tables III and. ~ contain the turf rat:f,l'Igs
taken at the end of the trial 1n m:tl:l-betober. -COIlIPU'isonsof the turf scores
between tables land III and II andr-J will clearly,lNu this out.
The treatments that did nots!9J'!ificantly lowel';the turf score are shown
in tables I and· II. Whenthe soil was treated at, ~prior to, seeding only 41
treatments out of a total of 240 failed to significantly reduce the turf s~ore.
Twenty-one of these 41 treatments were associatedw1th the use of calciumJ)%'0pyl
arsonate and the combination ofca1c~um propyl and 'flcium methyl arsonate..-.
Diphenatrile and the light rate :of ~ndane plus Chl~ane accounted for over
half of the other treatments that did not significantly lower the turf scOre.
In table II there are 91 out of, a total of 189 vestments that did not'
show a significant reduction in turf score. This wo.lfldindicate that there is
less injury associated with foliar applications of the chemicals used than with
soil treatments at or before seedin9~ Only triflura11~was unsafe to all grasses
at all rates and dates of application. As is shownQll the table, certain rates
of all other materials appeared safe to one or more grasses at one or more time
intervals. Diphenatrile, Bandane, Bandane plUS Chlo!dane, Dacthal Gl.5 SY, and
the combination of calcium propyl and calcium methyl arsonates appeared to.be
relatively safe, to use at certain .rates or times." '
Two trends which appeared duril'l~. the test are a. interest. First, the
grasses with the largest seed were l~jured the least.~rom soil treatment with
chemicals. Injury was greatest tobentgrass, blue~s was intermediate 'and
fescue was injured the least. . , ' .
Second, when treating grasses ~(ter seeding, thet !time interval required
for safety depends somewhat on the, ra:t;e of establ1shrnef\1t.. Bluegrass is slaw to
establish and was injured more frequehtly when treated two weeks after seeding
than was the bent or fescue. At later treatment dat .. ;the blue was the most, ~
tolerant of the herbicides, bent W$s':totermediate and~f.scue was the most au'-
ceptible to injury~ , "