| Pest
Species |
Abbreviation |
Economic Thresholds |
Corn Leaf Aphid
Rhopalosiphum maidis
English Grain Aphid
Sitobion avenae
Bird Cherry-Oat Aphid
Rhopalosiphum padi
|
(CLA) |
Fall - 25 aphids
per foot of row
Spring - 100 aphids per foot of row
Alternative thresholds - 20 aphids per stem in the seedling stage;
50 aphids per stem in the boot stage. If grain is heading, treatment is recommended only
if high aphid populations are causing the flag leaves to turn yellow. If grain is in dough
stage, treatment is not recommended. |
Armyworm (True)
Pseudaletia unipuncta
|
(TAW) |
6 or more larvae per linear foot
of drill row and
before head lipping is noted.
Note: If heavy parasitism is noted, the population will typically be
controlled without an insecticide application. |
Armyworm (Fall)
Spodoptera frugiperda |
(FAW) |
None established. Seldom a major
problem. Treat if new growth is severely damaged. |
Cereal Leaf Beetle
Oulema melanopus |
(CLB) |
An average of one adult or larva
per stem or flag leaf is found and damage is evident.
Note: If parasites are present and larvae are still small, the population
will usually be controlled by natural means. |
Grasshoppers
Melanoplus spp. |
(GH) |
20 grasshoppers per square yard
in noncrop areas around the field. |
Hessian Fly
Mayetolia destructor |
(HF) |
None. Rescue treatments are
ineffective. Plant after the "fly-free" date to avoid the pest. The presence of
10% or more of plants with "flaxseeds" indicates a poten- tially damaging
population. |
| The
economic thresholds were found in the "Field Crop Scouting Manual" of the
University of Illinios Cooperative Extension Service. |
