Fall armyworm and leaf-footed bug are the two pests LSU AgCenter documents attacking corn in Louisiana, and they show up at different points in the plant’s life: the armyworm chews into the whorl within weeks of emergence, while the leaf-footed bug punctures developing kernels once silks appear. Everything else on the state’s documented pest list targets other crops entirely.
Which pests attack corn in Louisiana
LSU AgCenter documents ten garden pests for this territory: Cowpea curculio, Crape myrtle bark scale, Fall armyworm, Leaf-footed bug, Pepper weevil, Pickleworm, Squash bug, Squash vine borer, Tomato pinworm, and Vegetable weevil. Only two of them have any business on a corn stalk.
Fall armyworm is the one to watch. It feeds inside the whorl of young corn plants and later moves into the ear tip, and Louisiana’s heat load, 70.7 days a year reach 90°F or hotter, keeps this pest active and reproducing across most of the growing season instead of tapering off after one flush.
Leaf-footed bug is the second. It is a generalist that pierces developing seeds and fruit across a wide range of garden crops, and corn kernels forming behind the silks are exactly the kind of soft, filling tissue it targets.
The rest of the list has nothing to do with a corn patch, and it is worth saying why, because a gardener who spots one of these on a search result and assumes it explains torn corn leaves will misdiagnose the problem.
- Cowpea curculio attacks southern peas and cowpea pods, not corn.
- Crape myrtle bark scale is a scale insect on ornamental crape myrtle trees, nowhere near a vegetable bed.
- Pepper weevil is specific to pepper fruit and buds.
- Pickleworm and squash bug and squash vine borer all target cucurbits, meaning squash, melons, and cucumbers.
- Tomato pinworm mines tomato leaves and fruit.
- Vegetable weevil feeds on root crops and leafy greens, not on a grass-family crop like corn.
LSU AgCenter documents a short list of true corn feeders for this territory, and that shortness is the finding, not a gap to fill in with pests from other states.
When each one shows up, and what it does first
Louisiana’s frost calendar sets the outer edges of the season, and it behaves differently here than almost anywhere else in the country. The last spring frost falls between January 18 and February 8, and the first fall frost arrives between December 17 and January 8, which means roughly one year in seven at the reference station sees no freezing temperature at all. That long, mild stretch is exactly why pest activity here does not wait for a calendar month, it starts as soon as the plant is up and stays possible almost the whole time the crop stands in the ground.
Sweet corn cannot go in the ground right after that last frost window closes. The seed needs soil above 60°F to germinate reliably, which comes well after the frost date itself, and from there the crop needs 60 to 90 days to reach harvest. That window has to close before the first fall frost, and in a territory where summer heat runs long, the growing window is generous, but it also gives fall armyworm more time to cycle through the planting than a shorter northern season would.
Fall armyworm damage appears first as ragged, elongated holes in the newest whorl leaves, sometimes with a scattering of sawdust-like frass caught in the leaf funnel. That damage shows up early, within a few weeks of the seedlings pushing up, and it can return through the season because the state’s summer heat load supports repeated activity rather than one single wave.
Leaf-footed bug damage shows up later, once the plant silks and begins filling ears. The first sign is not a chewed leaf but a small puncture or dimple on individual kernels, sometimes with a shrunken or discolored kernel next to healthy ones on the same cob. That timing lines up with the ear-fill stage of the 60-to-90-day maturity window, not with the seedling stage where armyworm shows up.
Telling the damage apart from everything else
Corn grown in Louisiana’s heat load carries plenty of stress that has nothing to do with insects, and mixing the two up leads to wasted effort. The tell is where the damage sits on the plant and how it is shaped, not just that something looks wrong.
| Symptom | Possible cause | What separates it |
|---|---|---|
| Ragged holes in the newest whorl leaves, sawdust-like debris | Fall armyworm feeding | Damage concentrated in the tight, unfurled leaves at the top, not scattered evenly |
| Small punctures or dimples on individual kernels | Leaf-footed bug feeding | Damage appears kernel by kernel after silking, not across whole leaves |
| Pale striping between leaf veins, older leaves affected first | Nutrient deficiency | No chewed tissue or puncture marks, just discoloration that follows the leaf’s vein pattern |
| Leaves rolling inward, curling at midday | Drought stress during the state’s high-heat stretch | Leaves recover somewhat overnight or after watering, insect damage does not |
| Streaked or mosaic leaf pattern, stunted stalks | Viral or fungal disease | Pattern spreads plant to plant in a patch rather than showing single chew marks |
| Snapped stalks or torn ears near ground level | Mechanical or animal damage | Clean breaks or bite marks from a larger animal, not the fine feeding marks insects leave |
None of this is a substitute for someone actually looking at the plant. A gardener unsure which column their corn falls into should bring a sample, or a clear photo of the damage in place, to a local extension office rather than guess from a symptom list.
What actually works here, and what is a waste of time
Timing beats treatment in a season this long. A physical barrier such as fine mesh row cover placed over young plants before the whorl stage keeps fall armyworm moths from laying eggs there in the first place, and it costs nothing in labor once it is up. Pulling that cover before tasseling is necessary though, since corn needs open pollination once tassels form.
Planting corn in blocks of three or more rows, rather than one or two long single rows, does double duty. It is the shape Utah State University Extension recommends for reliable wind pollination, and it also makes it far easier to walk the block and spot early whorl damage before it spreads, instead of scanning a thin line of stalks from a distance.
Keeping different sweet corn types from tasseling at the same time matters too, not for pest control directly, but because a plant already weakened by inconsistent pollination shows stress that gets mistaken for pest damage, muddying the diagnosis. The source gives no separation distance between types, only the timing rule: avoid overlapping tassel dates.
What does not work is reaching for a broad treatment without confirming which pest, or any pest, is actually present. Louisiana’s extension service is the one that knows what is currently labeled for use on corn in the state, and a homeowner guessing at a product off a general gardening site risks treating for the wrong problem, or treating when the damage was drought stress or a nutrient gap all along. Scouting the whorl and the ear tip regularly, especially during the heat-heavy stretch when 70.7 days a year hit 90°F or above, catches problems earlier than any single spray timed by guesswork.
Where to check this for your own county
LSU AgCenter is the service that documents these pests for Louisiana, and its parish extension offices are the next step for anyone seeing damage that does not clearly match armyworm or leaf-footed bug feeding. A state-level list says what has been found across Louisiana as a whole, it does not say what is active in one particular garden this season.
That gap matters more here than in many states, because Louisiana’s own frost data shows a real split: south Louisiana barely freezes some years, while north Louisiana freezes far more reliably. A pest cycle that runs almost year-round near the coast can behave on a tighter schedule further north, and a county office in one part of the state may be seeing pressure that a garden two hundred miles away is not.
The parish extension office can also confirm which of the two documented pests is actually present through a sample or a photo, rather than a guess from a written symptom list, and it can point to what treatment options are currently labeled for corn in Louisiana specifically. That local check is the useful next move, not another round of searching for a symptom match online.
Common questions
Does corn earworm show up in Louisiana gardens?
It is not on the pest list LSU AgCenter documents for this territory on this site. A parish extension office can confirm what is present locally.
Can row covers stay on corn the whole season?
No. Covers need to come off once tassels form, since corn relies on open-air wind pollination to fill ears.
Is leaf-footed bug damage the same on every ear?
No, it typically appears kernel by kernel rather than across the whole cob, which is one way to separate it from a plant-wide stress problem.
Why does the fall frost window matter if fall armyworm is a summer pest?
Because the frost window sets how long the growing season runs, and a longer frost-free stretch, combined with 70.7 days a year above 90°F, gives the pest more cycles to return to a planting before harvest.