What eats beet in Iowa, according to Iowa State University Extension’s documented pest list, comes down to three generalist feeders: grasshoppers, the common stalk borer, and the Japanese beetle. Grasshoppers and beetles chew leaves through the growing season; the stalk borer goes after seedling stems in late spring. The rest of the extension’s list targets other plants entirely.
Which pests attack beet in Iowa
Iowa State University Extension documents nine garden pests for this territory: common stalk borer, grasshoppers, iris borer (Macronoctua onusta), Japanese beetle (Popillia japonica), lily leaf beetle, spotted cucumber beetle, squash bug, squash vine borer, and striped cucumber beetle. That’s the full list this service tracks here, and it isn’t padded with anything beyond it.
Not all nine have any business in a beet row. The iris borer feeds exclusively on iris rhizomes and foliage, so a beet bed a hundred feet from any iris planting won’t see it. The lily leaf beetle is a specialist on true lilies and fritillaria; it has no reason to touch a beet leaf. Squash bugs, squash vine borers, and striped cucumber beetles all key in on cucurbits, squash, pumpkin, cucumber, melon, and their vines. A striped cucumber beetle will land on a beet plant the way it might land on a fence post, but it isn’t there to feed. The spotted cucumber beetle is a broader feeder than its striped cousin, going after corn roots and cucurbit foliage, but it isn’t among the species extension records as a beet feeder here.
That leaves three that plausibly show up in a beet planting: grasshoppers, which strip foliage on almost anything green when populations build; the common stalk borer, whose larvae tunnel into the stems of a wide range of broadleaf garden plants, beet and chard among them, after moving off weedy hosts like giant ragweed; and the Japanese beetle, a generalist skeletonizer that will work over beet leaves along with roses, grapes, and dozens of other plants when its preferred hosts are crowded or gone.
The short version: three of nine named species are realistic suspects on beet in this state, and the other six belong to different gardens entirely, iris beds, lily plantings, or the squash patch. If a gardener finds something chewing on beet leaves that doesn’t match one of these three, Iowa State University Extension is documenting it under a different name, or it isn’t a species this service currently tracks here.
When each one shows up, and what it does first
Beets in this state go into the ground once the frost-free window opens, and NOAA’s 1991-2020 climate normals put the last spring freeze for the region between April 12 and April 24, with Iowa State Extension’s longer county records running roughly four days later in spring. Everything below tracks off that seeding date, not off a named calendar month, because a beet planted right at the frost line behaves on a different schedule than one held back a few weeks for wet soil.
The common stalk borer is the earliest problem. Its larvae move out of weedy borders in the weeks after seeds go in, and the first sign is rarely a visible insect at all: a single beet seedling wilts while its neighbors look fine, or a young stem shows a small entry hole near the soil line with a bit of frass pushed out. By the time the wilting is obvious, the larva is already inside the stem, which is why this one gets caught by prevention rather than by spotting it early.
Grasshoppers build through the season rather than arriving on a single date. Numbers stay low early, then climb as roadside grasses and field edges dry out, so the first noticeable damage is usually ragged, irregular holes chewed into leaf margins rather than a clean skeletonized pattern. Dry summers push grasshoppers into garden beds faster because their preferred grassy hosts brown off sooner, and a beet planting near a field edge or overgrown fence line sees them well before one tucked closer to a house.
The Japanese beetle shows up once beet plants are past the seedling stage and putting on real leaf area. Its feeding leaves a distinctive lacy, skeletonized look, the beetles chew between the veins and leave the vein network standing, and they tend to feed in small clusters rather than as single insects. This one is visually the easiest of the three to confirm, because the damage pattern and the beetle itself both stand out clearly against beet foliage.
Telling the damage apart from everything else
Chewed or wilted beet plants don’t always mean an insect. Beets carry their own failure points that have nothing to do with pests, and mixing them up leads to spraying or hand-picking for a problem that a garden hose or a shade cloth would actually fix.
Utah State University Extension notes that water stress in the first six weeks after seeding causes premature flowering, or bolting, while heat above 85 F combined with water stress later on makes the root turn woody. These are two separate failures with two separate windows, not one general “keep it watered” problem, and neither one involves a chewed leaf.
| Symptom | Likely cause | What distinguishes it |
|---|---|---|
| Seedling wilts suddenly, plant otherwise upright | Common stalk borer | Small entry hole and frass near the soil line on the stem |
| Ragged, irregular holes along leaf edges | Grasshoppers | Damage worsens through a dry stretch and matches nearby garden or edge foliage |
| Lacy, skeletonized leaf tissue between veins | Japanese beetle | Beetles feeding in small clusters, visible on the leaf itself |
| Plant bolts to flower early, no leaf damage | Early water stress | Happens within roughly the first six weeks after seeding, not tied to any chewing |
| Root turns fibrous or woody | Heat above 85 F paired with dry soil later in the season | No foliage damage; root texture is the only sign |
| Pale or yellowing leaves, no holes | Nutrient deficiency or compacted, poorly drained soil | Uniform across the row rather than patchy, and no chew marks |
A gardener looking at a damaged beet bed has a clean way to sort this: is there a hole, a chew mark, or a beetle on the plant itself? If not, the cause is more likely watering, heat, or soil than any of the three species above. When it isn’t obvious which one applies, the county extension office can look at a sample rather than guess from a description alone.
What actually works here, and what is a waste of time
On a season this short, timing beats almost anything applied after the fact. A lightweight floating row cover set over beet rows right at seeding, and left on until plants are past the vulnerable seedling stage, keeps stalk borer moths and early grasshoppers off the crop without needing to identify anything mid-season. The cover has to go on before the frost-free window closes the seedling stage, not after damage shows up, because by the time a stem is hollowed out or a leaf is skeletonized, the cover is protecting an already-damaged plant.
Clearing weedy borders, giant ragweed in particular, ahead of seeding cuts down the stalk borer’s staging ground, since larvae move from those weeds into garden crops rather than starting there. Hand-picking Japanese beetles in the cooler part of the day, when they’re slower and more clustered, works reasonably well on a small planting and doesn’t require any product at all. Keeping garden edges mowed reduces the grassy habitat that lets grasshopper numbers build up next to a beet row.
What wastes time: treating a wilted seedling for stalk borer once the wilting has already set in, since the larva has usually finished its damage inside the stem by then; and spraying broadly for “bugs” without confirming which of the three species is actually present, since a treatment aimed at grasshoppers does nothing for a stalk borer already inside a stem. This site doesn’t recommend a specific product, rate, or active ingredient, because what’s labeled and legal for use on beet changes by state and by year, and Iowa State University Extension’s county office is the only source that keeps that current.
Where to check this for your own county
Everything above comes from Iowa State University Extension’s statewide pest documentation, and a statewide list describes what’s been recorded across the state, not what’s necessarily in one particular garden. Pest pressure inside Iowa varies by county, by how close a property sits to field edges or established weed cover, and by how wet or dry a given season runs.
The next concrete step is a call or visit to the local county extension office, which can confirm whether a specific damage pattern matches one of the three species discussed here or something the statewide list doesn’t cover. County staff can also identify a sample directly rather than working from a written description, which matters most for damage that doesn’t cleanly match the stem-hole, ragged-edge, or lacy-leaf patterns above.
A soil test through the same extension system is worth pairing with a pest check, since some of what looks like insect damage traces back to the soil itself, drainage, compaction, or nutrient gaps that show up as discoloration rather than chewing. The state’s representative soil, mapped under the Tama series, runs well drained with about 3.5 percent organic matter and a surface pH near 6.5, but that’s a statewide reference point, not a reading of any one yard. A garden built on fill, river-bottom ground, or hill soil can differ from it completely, which is exactly why a local test matters more than a state average.
Common questions
Does the striped cucumber beetle ever bother beet plants in Iowa?
Iowa State University Extension documents it as a species tied to cucurbits, squash, cucumber, melon, and pumpkin, not to beet. A beetle landing briefly on a beet leaf isn’t the same as it feeding there.
Can grasshopper damage on beets be confused with hail or wind damage?
Wind and hail tend to tear leaves unevenly across an entire row at once, while grasshopper feeding shows up as chewed margins that spread gradually as populations build through a dry stretch.
Is bolting in beets caused by an insect?
No. Utah State University Extension attributes early bolting to water stress in roughly the first six weeks after seeding, a soil and watering issue, not a pest.
Should beet seedlings be covered right after seeding or only after damage appears?
Right after seeding. A physical cover works by keeping stalk borer moths and early grasshoppers from ever reaching the stem; once stem damage is visible, the cover can no longer prevent it.