Vol. 54—2000 - NorthEastern Weed Science Society

The Effect of Total Postemergence Herbicide Timings on Corn Yield
D. B. Vitolo, C. Pearson, M. G. Schnappinger, and R. Schmenk
ABSTRACT
Replicated field trials were conducted in Livingston, New York, in 1996, 1997,
and 1998 to evaluate the effect of pre- and postemergence herbicide programs
on weed control and corn grain yield. Bicep II Magnum brand herbicide
applied preemergence was compared to three timings of a total postemergence
herbicide program using either Exceed + Accent + Banvel brand herbicides
(1996) or Roundup Ultra brand herbicide (1997-1998), and ro Bicep II
Magnum brand herbicide followed by a postemergence program.
Posremergence timings corresponded to average weed heights of 2 to 4, 6 to 8,
and 10 to 12 inches. In all years, the preemergence treatments resulted in >
90% control of all weeds, and the postemergence applications killed all
emerged weeds. The weed spectrum in the test area included giant foxtail
(Setaria faber; Herrm.), common ragweed (Ambrosia artemisiifolia L.),
common lambsquarters (Chenopodium album L.), velvetleaf (Abutilon
theophrasti Medik.), and wild radish (Raphinus raphanistrum L.).
In both 1996 and 1997, yield loss was correlated with delaying postemergence
applications, with the drier year (1997) resulting in higher percentage losses
than 1996. Only the 2- to 4- inch postemergence timing resulted in yields
similar to the preemergence treatment.
In 1998, a wet spring was followed by dry summer. The 2-to 4-inch
application timing was too early, and new weeds germinated to compete with
the crop. The 10-to 12- inch application timing was too late, with the larger
weeds reducing yield. Only the 6- to 8- inch postemergence timing resulted in
yields similar to the preemergence treatment.
In all 3 years, the application window for total postemergence treatments was
narrow, ranging from 10 to 21 days. Given the challenge that herbicide
applicators have in covering their acres, and the unpredictability of each season
(weather, wet fields, and proper timing), a preemergence herbicide application
followed by a postemergence herbicide, when needed, provides corn growers
with an excellent strategy for flexible and effective weed control.
11 R&D Station Manager, Regional Research Manager, Senior R&D Scientist,
R&D Scientist, Novartis Crop Protection, Hudson, NY 12534
17