Vol. 16—1962 - NorthEastern Weed Science Society

RESULTS
Pre-emergence treatment: The efrEf~ts of chemicals
applied Apr!l 27 - May 1, 1961are presen~ed in Table 1. Rainfallon
the plot area between April 29 arid May 3 was 0,78 in.
First crabgrass emergence was noted in the control plots on
May 15th. -, .
S37
Excellent control of crabgrass with no injury to other
grasses was given by all rates of zytron (-bt:rt1fliquid and
granular formulations), dacthal (wettable powder and granular),
diphenatrile (diphenylacetonitrile) and dipropalin. Diphenylacetonitrile
(Agrico formulation) gave good control (over 90%.1
at the lower rates and excellent controla'e--the highe st rate.
Calcium propyl arsonate was good at 60 Ib/A but not satisfactory
at lower rates. This chemical had a strong inhibitory effect on
clover.
. Pax (36.5% metallic arsenic) and Chip Cal (50%
tricalcium arsenate) gave good control at the highest rates but
were poor at lower rates..T:r.:H'luralin causedmarked burning of
all plants in the plots and, therefore, was not satisfactory
even though it gave 100% control of crabgrass.
Similar results were 0 btained in 1960 -d.n an experiment;
in which zytron (liquid and granular), dacthal (granular) and
calcium arsenate were tested,
Residual effects: .The 1960 plo;ts WEl!'eunintnine.d and
observations-on-the:residual effects were made periodically dUring
the summer of 1961. Some crabgrass was found in all the ;
plots, but those treated with all rates of zytron (a, 16, 24 Ib/A
both liquid and granular) and those treated with tricalcium
arsenate at 15 Ib/1000 sq. ft. or with dacthal granular at
15 Ib/A, had considerably less than the others. Control with
both 16 and 24 Ib/A of zyYron exceeded 90% throughout the s\.Ulllller.
The g Ib rate gave fair control (50-70%) as the granular formulation,
but liquid zytron at a Ib/A did not have as much residual
effect.
In another experiment, set up to stnrdy the effectiveness
of application of pre-emergence crabgrass herbicides in the fall,
plots were treated on Nov. 14, 1960 with zytron, liquid and
granular (10,20,30), dacthal, wettable powder and granular (10~15,
20), and tricalcium arsenate.(5-,7!,10,15).Rates of zytron and
dacthal are Ib active/A, and of tricalcium arsenate are Ib active/
1000 sq. ft. Only the plots receiving the low rate of dacthal'
granular and the lowest two rates of tricalcium arsenate weren()t
completely free of crabgrass on July 21, 1961'" 'However, by August
31, crabgrass was noted in all plots except.~hose receiving 20 or
30 Lb of zytron or 20 Ib of d/icthal, al.t.hough, plo t s treated with
~tron 10, dacthal 15, or tricalcium arsenate 15, contained on~y a
few crabgrass plants. On11 the: highest rate ~f zytron caused any
turf dffinage (some thinning) and even these piots recovered by early
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