HERBICIDE
INJURY DIAGNOSIS - CORN
Germination/Emergence
Poor germination and uneven
emergence
- not typical of herbicide
injury, however, incorporating P rowl (not labeled for PPI in corn) or misapplication
of any DNA herbicide can cause poor emergence. "Clubbed-roots" should be visible.
Leaf-out underground
- Axiom, Define, Dual
II Magnum, Eradicane, Harness/Surpass, Lasso, Outlook, and premixes containing
these herbicides may cause leaf-out under cold and wet conditions. Crusted
or cloddy soils may cause this also.
Seedling/Young
plant
Buggy-whipping/twisting/leaf
crinkling
- characteristic of shoot
inhibitors such as Axiom, Define, Dual II Magnum, Eradicane, Harness/Surpass,
Lasso, Outlook, and premixes containing these herbicides. Usually occurs under
cold and wet soil conditions and is often temporary. Dicamba, 2,4-D, or these
two tank-mixed with a shoot inhibitor may cause similar symptoms but corn
may be rolled tighter and lay more horizontal to soil surface. The longer
the buggy-whipping is present the greater the potential for yield loss.
Stunted plants/interveinal
yellowing and/or purpling of leaves
- misapplication or carryover
of ALS-herbicides such as Backdraft, Canopy XL, Classic, Extreme, FirstRate,
Pursuit, Raptor, Scepter, Squadron, and Synchrony STS. Check plant for a "bottlebrush"
appearance on lateral roots. Fields affected by carryover may take on an uneven
appearance with a series of stunted plants followed by healthy plants, intermittently.
Persistence of Scepter, Pursuit, and premixes containing these herbicides
will increase at soil pH of 5.5 or less and under drought conditions. Persistence
of chlorimuron and premixes containing chlorimuron will increase with soil
pH above 6.8.
- soil applications of
Hornet and Python may cause injury under cold and wet conditions.
- Application of Accent,
Accent Gold, Basis, Basis Gold, Beacon, Celebrity Plus, Exceed, Hornet, Lightning
on Clearfield Corn, Python, Spirit, or Steadfast in the same season as Counter
(15G or CR), Phorate, or Thimet soil insecticides may cause the above symptoms
including severe leaf margin crinkling and "onion-leafing".
Stunted plants/white leaves
and/or shoots
- misapplication of glyphosate
at a low dose (usually at spike stage).
- Balance or Callisto may
cause these symptoms. Severe injury with Balance may include severe stunting,
leaves turning necrotic, buggy-whipping, and stand loss. Injury with Balance
is most common under the following conditions: sandy soil types; shallow planting
depth (less than 1.5 inches); cold and wet soil; spray overlaps; soil pH approaching
7.5; organic matter less than 1.5 %.
Stunted plants/short swollen
and/or "clubbed roots"
carryover or misapplication
of DNA herbicides such as Balan, Prowl, Sonalan, or Treflan.
White/bleached leaves
- misapplication or carryover
from Command or Command Extra. The plant will usually grow out of slight discoloration.
However, if more than 75 % of the plant tissue is white the plant will probably
die. Carryover is most likely on soils with a pH below 5.5.
- postemergence application
of Callisto. Increased injury when applied after a soil or postemergence application
or tank-mixed with organophosphate insecticides or when mixed with methylated
seed oil.
Leaf burn on leaf margins
of older leaves
- photosynthetic inhibitors
may cause yellowing (chlorosis) of leaf margins followed by death (necrosis)
of the oldest leaves on the plant. Herbicides in this group include atrazine,
Sencor, Lorox, Princep, and premixes containing these herbicides. Injury is
more likely at high pH (above 7.2).
Speckled to burned leaves
- postemergence applications
of Aim, Buctril, Resource, Atrazine plus crop oil concentrate, or Callisto
(only the first few days after application). Effects are usually temporary
unless a large percentage of the plant is brown.
Yellow to translucent color
on new leaves
- misapplication of Assure
II, Fusilade DX, Fusion, Poast, Poast Plus, or Select. The whorl will be easily
pulled from the rest of the plant with a characteristic collapsed brown tip
on the end near the growing point.
Speckled leaves due to drift
- Aim, Cobra, Flexstar/Reflex,
Gramoxone Max, Resource, or Ultra Blazer drift. Usually only cosmetic injury.
Bent or "goose-necked" stalks/fused
brace-roots
- postemergence applications
of growth regulator type herbicides such as 2,4-D, dicamba, and premix products
containing these herbicides. Plants may become brittle and prone to lodging.
More severe during periods of high temperatures and rapid node elongation.
Veinal chlorosis or browning/collapse
at leaf arch/buggy-whipping
- carryover of Flexstar
or Reflex. Occurs withlate applications of Flexstar/Reflex, dry soils, and
early corn planting. Plants may die in areas of spray overlap, but most corn
will survive injury.
Pollination
Poor pollination
- late season applications
of 2,4-D or dicamba at "tassel" to "dough" stages of development.
- late applications of
Lightning on Clearfield corn.
Maturity
Ear-Pinching
- postemergence broadcast
applications of Accent, Accent Gold, Basis Gold, Celebrity Plus, or Steadfast
after corn has reached 6 collars. This is characterized by the base of the
ear having normal number of kernel rows and the upper part of the ear having
about 50 % fewer rows.
Corn,
Soybean, Wheat, and Alfalfa Field GuideBulletin 827