Vol. 16—1962 - NorthEastern Weed Science Society

Control with the granular formulation of INA was poor.
Potassium cyanate was used only once. Iteaused discolorati:on
for a few days, and gave good control of, the crabgrass pr-esent at
time of application. The eff1ectiveness of-calcium propyl arsonate
when applied post-emergence to the crabgrass was interesting. At
60 Ib/A (of active material) good control was' producted by
applications from April 29 to June 27. f
541
In another experiment, c~rtain chemicals that usua~l~
have been regarded as pre ...em~rgence herbicides for cr-abgr aas "
aontrol were applied shortly ',after germin~ti:on (May 23, 1961) when
the crabgrass seedlings were-in the 2-3 le~f stage. The results
of this experiment are presented in Table;~. ,All of the '
herbicides listed gave good .control when ~sed as early postemergence
treatmentj· ' "
Table. 4: Effe.cts of certain chemicals on":crabgrass when
applied soon after emergence.
Herbicide Rate Control Turf
(lb/A) (0-4) * Injury
Calcium propyl 40 3 None
arsonate 60 4 None
(No-crab)
Diphenatrile
(Lilly)
40 4 Slight
Zytron (liq.) 16 4 None
Dacthal (gran.) 15 4 None
* o • no control; 4 • 100%control
DISCUSSIQ.!::!
~n the basis of two years results, the outstanding preemergence
crabgrass herbicides in the Guelph, Ontario area
appear to be zytron and dacthal. Data for 1961 alone indicate
that diphenatrile and dipropalin could be as good. However,
growing conditions were excellent for turf throughout the summer
of 1961, and it is probably safe to aSSillne that the chance of
obtaining good control would be better than if the turf grasses
offered little competition.
Several chemicals applied after crabgrass emergence
(Potassium cyanate, ~lA, ~, and ~lA) controlled crabgrass, but
more than one application per season seemed to be required and
some degree of turf injury was brou~lt about by each. The use of
some "pr-e -emer-gence " herbicides (calcium propyl arsonate, zytron