Vol. 16—1962 - NorthEastern Weed Science Society

500
Da1;ejJ01 e~uations
~,a.;t'ollClW&I.,
, . " l r I
,.AMCHEJ{ Research ~t June 20, JulT 24, August 24 "
: "September 29
, 08k., Twrace CCt r·",,· June 20, Ju4r 27, August 24
September 29
~.
',i1~e Valley GCs June 27, JulT 22, ,Ootober 11
./ '"j '.
( r', .i
iThe sp,~.~~f·" ~961 ~,.t~'~:Old and~:~1l)kt\,~he PhUadelphia.',; sr:
area,as. it wasin many other parts of the North... , crabgrass emergence
was two weeks to a month later than usual, and growth after emergence was
very slow until around the middle of June. Muchot the emerged crabgrass
was still in the 2 to 4 leaf ,s'tap,on June let.' _ ,
, ' . Ra:lntallwas constant ,\brR'I,1ghouthe SUJMr· and temperatures were
high enough to t,Cl(Drcontinuous ,prmaxim'lllll emergence of crabgrass. There
..ere no distinct. ~.ods of crabgrNs emergence and growth as is 'lSSualin
our &r84.0.. ,~
\'r
Hhile no n'lllllerical counts of the actual stand of crabgrass per
unit areaw.ereT~to compare~.rstand to previoUs seasons, visual
~uatione .:1ndica:ted.,that the nat'Ol'alcrabgrass iDtestation was much more
uaUom andseV~than in prev:1oul years. Thus, it is possible that in
the past seaso~.;8Il.ef:fective c~cal producing 9Sto 98 per cent control
may have left 10 to 15 crabgrass plants in a 50 to .100 square foot area.
In 1961, on the ,other hand, 95 to9S per cent control of amuoh larger
number ofsp%'out~gC1!E!bgrass seedS!imayhave allowed 50 to 75plants to
develop.in the881lle plot area.' J:
Whentransformed into the visual estimates used in our eva+.ua~ions,
the larger n'lllllberof plants present would greatly reduce apparent contfo.l.i
Thus, a chemical ~ have controlled 50 per cent of the crabgrass plants
actualJ.¥· emerging,bU.t those ~g plants wou14:'beenough to completely
intestthe plots ,and wew~ld8ft;].lIa'te this as' n(j,i,~aren't control.' .,:' ,,'
This probably accounts for the reduced, etleotiveness 'of material's
such as dacthal, zytron and tricalci'lllll arsenate, wh1ch have been consistently
effect~ve :in our, 'tUttt.1t1- previau.::years. Theon1.:j liUlt.erialsproviding _
more than 80 p.. oent· control t~th$., season ·1fMtritluraJ.in at 4,"~ ,
and 8 lb/A and d1lll'opalin at 8 lb/A.
In 1960, salcium propyl arsonate showed IIltcellent tolerance to
established turf and new turf planted before or after application, good
post-emergence activity on crabgrass, and aat:lsfactory seasonal pre-emeraence
crabgrass control.