Sweet corn gets eaten in stages, and each stage has its own diner. Seedlings lose leaves or whole plants to pests working at the soil line. Young plants get chewed in the whorl. Silking plants lose silks and ear tips to caterpillars, and ripening ears draw birds and raccoons. Match what you see to the crop stage and the list of suspects shrinks fast.
Which pests attack corn in Texas
Texas A&M AgriLife Extension Service documents the insects active across the state, and its county offices turn that list into names for your ground. For a corn patch, the entries that matter sort into five groups by how they feed.
- Soil-dwelling feeders that chew seeds and cut seedlings at the base.
- Caterpillars that eat leaves and hide in the whorl, the tight funnel at the plant’s center.
- Caterpillars that feed on the silks and work down into the ear from the tip.
- Borers that tunnel inside stalks and shanks.
- Birds and raccoons, which show up once the kernels turn sweet.
Before you name any insect, note which part of the plant is damaged and what growth stage the corn is in. Those two facts rule out most of the list in a minute, and they are exactly what an extension agent will ask you first.
When each one shows up, and what it does first
Calendar months mislead here, because Texas spans four USDA zones. The reference station near Houston, on the mild Gulf end, has a mean last spring frost window of February 4 to March 1 and a mean first fall frost window of December 1 to December 19 (NOAA NCEI Climate Normals, 32F freeze probabilities). The Panhandle freezes months earlier in fall and later in spring. Soil reaches 60 F well after the last frost, and the crop then needs 60 to 90 days from planting, so pest timing is best counted from your own planting date.
The first stretch runs from sowing to a few weeks after emergence. The first thing you see is a gap in the row, a seedling snipped at the base, or a center leaf that wilts while the outer leaves stay green. Scratched soil and pulled sprouts suggest birds.
The next stretch comes as plants grow toward knee height. Whorl feeders leave a distinctive sign, a row of ragged holes across leaves that unfold from the funnel. Droppings sit in the funnel like damp sawdust. Plants often outgrow a light infestation, so the question is how much of the leaf area is gone.
Tassels and silks come next. Bored tassels, broken tassel stems, and a stalk bent at a tunnel are the early signs of borers. Silks that look cut short, or are matted with droppings, mean something is feeding at the ear tip. Chewed silks can also interfere with pollination, which shows up later as an ear with gaps in the rows.
Ripening is the last stretch, and it is the one with the clearest timer. Ears are ready when the silks brown and the kernels feel full, and that is the same window when animals find them. This clock answers a different question than the 60 to 90 days from planting. The planting clock tells you whether the crop fits your season at all, which Will Sweet Corn Ripen in Texas? works through. The silk clock tells you which week to pick.
Confirm ripeness with three signs together: dry brown silks, husks still moist and green, and milky juice when you puncture a kernel. Raccoons often strip ears right at that stage. Husks pulled down, kernels gnawed, and stalks flattened across the row are the signature. A summer with 102.4 days at or above 90 F at the reference station also speeds sugar loss in the kernel, so do not leave ripe ears on the plant to wait for a weekend.
Telling the damage apart from everything else
A lot of corn problems look like insect work and are not. Hail, wind, heat, dry soil and thin nutrition all leave marks that fool people into spraying. The table lists the usual look-alikes and the sign that separates them.
| What you see | Possible causes | What settles it |
|---|---|---|
| Ragged or shredded leaves | Caterpillar chewing, or hail and wind tearing | Droppings in the funnel suggest insects. Tears running the same direction on every plant suggest weather. |
| Pale or yellow leaves, starting at the tip of lower leaves | Nutrient shortage, or a sap-feeding insect | A yellow V along the midrib on older leaves points to nutrition. Look on the leaf underside for insects and sticky residue. |
| Leaves rolled at midday | Water stress | Leaves that unroll by evening point to water. Leaves that stay rolled need a closer look at the base of the plant. |
| Ear with gaps or a bare tip | Poor pollination in heat or drought, or kernel feeding | Peel the husk. Chewed kernels with droppings mean feeding. Clean, undeveloped kernels suggest pollination. |
| Spots or streaks on leaves | Leaf disease | Defined lesions with no holes and no droppings fit disease, so take a sample to the county office. |
| Plants knocked flat | Wind, animals, or a tunneled stalk | Split a stalk lengthwise. A tunnel with droppings answers the question. |
Split a stalk or peel an ear before you decide on anything. What is inside tells you more than the outside ever will.
What actually works here, and what is a waste of time
A physical barrier set at the right moment beats a treatment. Row cover over seedlings keeps soil-line and leaf feeders off young plants, but it has to come off before tassels open so pollen can reach the silks. Netting or wire around the patch keeps birds away from sprouts. For raccoons, fencing needs to go up before ears reach the milk stage, since animals that learn a patch keep coming back.
Garden shape matters too. Utah State University Extension recommends planting in blocks of three or more rows, which helps wind pollination fill the ears and makes the patch easier to fence. Sweetness depends on what tassels nearby, so su, se and sh2 types should not tassel at the same time. Separate their plantings and stagger sowing dates.
Soil temperature is the other lever. Clemson Extension says: “Do not plant before the soil temperature at the 4-inch depth is at least 50 ºF. Wait to plant extra-sweet varieties until soil temperatures reach 65 °F.” Use a thermometer at 4 inches, not a calendar date, because seed that sits in cold soil germinates slowly and gives soil feeders more time at it. Extra-sweet seed sown at 50 F can rot where ordinary sweet corn would have come up. When you do pick, Clemson notes that “sweet corn loses sugar from the kernel rapidly at high temperatures” and can be stored “for about five days” under optimal conditions, losing sweetness each day. The su type loses sugar fastest, se holds it longer, and sh2 holds it longest. For the sowing window itself, see When to Sow Sweet Corn in Texas.
Several common efforts waste time. Spraying on a schedule before anything is identified wastes effort, and surface sprays cannot reach a caterpillar inside an ear or a borer inside a stalk. Scarecrows and shiny tape work for a few days until birds get used to them. Planting every row on one day ripens everything at once and leaves one window for animals to take it all. As for which products are registered for corn in the state, only the county extension office can answer that, and any label you read should be followed to the letter.
Where to check this for your own county
Pests vary inside a state, and sometimes inside a single metro area. Even within Houston, Hobby airport runs two weeks milder than IAH. A statewide list tells you what has been documented somewhere in Texas, and it cannot say what is feeding in your row.
The right place to ask is the county office of Texas A&M AgriLife Extension Service. Agents there see what has been active locally over recent seasons, which species tend to arrive at which growth stage, and what is currently registered for home garden use. They can also confirm whether a problem is an insect, a nutrient shortage, water stress or disease, which saves you from treating the wrong thing. For the bigger picture on varieties and planting, start at Growing Sweet Corn in Texas.
When you go, bring something concrete. Seal a damaged leaf or the insect in a container, or take clear photos of the whole plant, the damaged part, and a split stalk or peeled ear, with your planting date and the growth stage written down. The next time you set seed, ask the office which corn pests showed up last season and at what crop stage, then mark those dates beside your own planting date.
Common questions
Do I have to spray sweet corn in Texas?
Not always. Fencing, row cover removed before tassel, blocks of three or more rows, and regular row checks handle many problems without a spray. If damage keeps spreading, ask the county extension office which products are registered for your situation.
Why is the tip of my ear chewed?
Something fed on the silks and worked down the ear, or pollination was poor and the tip never filled. Peel back the husk. Chewed kernels with droppings point to feeding, while clean, small kernels point to pollination. A county agent can confirm.
How do I know when to pick before animals get it?
Watch the silks brown and the kernels fill out before you pick. Then check all three signs together: dry brown silks, green and moist husks, and milky juice from a punctured kernel.
Does planting in blocks help against pests?
It helps ears fill and makes the patch easier to fence. Blocks of three or more rows come from Utah State University Extension as a pollination rule, and a compact block is simpler to cover than a single long row.