How Do Leafhoppers Damage Leaves When They Feed?
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Leaves that turn mottled, brown at the edges or stunted can have many causes, but leafhoppers are one common insect behind that pattern. The question of how do leafhoppers damage leaves when they feed has a specific answer in the University of Illinois sources. Leafhoppers push a fine stylet into plant tissue, draw sap from the tubes that carry food, and release substances while they feed. The damage shows up in the leaves as cell death and distortion. This explainer follows that sequence and marks where the sources stop.
Quick answer
- Leafhoppers have a stylet, a tube-like mouthpart, that they push into the plant to reach the phloem, the tissue that carries food.
- Feeding tears and breaks cells, which can clog the phloem, and the insect releases substances that add to the injury.
- Leaf edges can die, giving brown to black margins, and new shoots can be stunted or deformed in severe cases.
- The Illinois Hort Answers page says the damage usually reduces growth rather than seriously harming the health of the tree.
What a leafhopper’s mouthparts do
Leafhoppers belong to the group of insects with piercing-sucking mouthparts. The Illinois Hort Answers page describes the leafhopper’s stylet as a tube-like mouthpart that the insect uses to pierce the phloem-conducting tissue. The Illinois IPM page explains the wider group. Insects in this group insert their mouthparts into the vascular tissues of plants, mainly the food-conducting tissues, and withdraw plant fluids.
This is different from chewing insects. The IPM page says chewing insects physically remove portions of leaves or flowers, or consume entire plant parts. A leafhopper does not remove a bite of leaf. It takes sap through a narrow tube, so the visible damage comes from the cells the stylet disturbs and from the plant’s response to feeding. For how plants themselves resist feeding insects, see how plants defend against insect herbivores and how leaf trichomes deter insect feeding.
Step one: the stylet tears cells
When the stylet enters the phloem, the feeding injures the tissue around it. The Hort Answers page says the feeding causes cells to tear and break into pieces. Those fragments can clog the phloem, which is the tissue that normally moves sugars and other food through the plant. A clogged phloem channel means that food cannot reach parts of the leaf and shoot as it should.
The IPM page adds that phloem-feeding insects have enzymes that break down the middle lamellae of plant cell walls. The middle lamella is the layer that glues neighbouring cell walls together. The page does not say that leafhoppers use this exact enzyme, so the enzyme point is a general statement about phloem feeders rather than a finding about leafhoppers specifically.
Step two: toxins and plant response
The Hort Answers page also says the insect releases toxins as it feeds, which causes additional injury to the plant. The page does not name the toxins or describe their chemistry. It reports the effect rather than the mechanism, so the article keeps to that level.
The result is that the damage is more than a mechanical puncture. The tears from the stylet and the injury from the released substances work together. Both happen at the feeding site, which is why the damage often appears along the leaf margins and across the leaf surface rather than in a single spot.
Step three: what the leaf looks like
The Hort Answers page describes the leaf symptoms directly. Leaves become mottled and show brown to black edges. Some cells, especially along the leaf edges, die, a condition the page calls hopperburn. Early red fall color can also appear on affected leaves. In severe cases, new leaves and shoots are stunted and deformed.
The page says this damage does not cause serious harm to the health of the tree, but it does reduce growth. That distinction matters for a gardener who sees a leaf with brown edges. The leaf may look unhealthy while the plant keeps living, although its growth can slow.
Why the sap-feeding habit affects plant nutrition
The IPM page explains why sap feeding is nutritionally demanding for the insect. Plants contain only 2 to 4 percent nitrogen overall, while the dry weight of most insects is between 8 and 14 percent nitrogen. Phloem sap contains only 0.5 percent or less nitrogen, according to the page. A phloem feeder must therefore consume a large amount of sap to get enough amino acids. The excess sap that is not used is excreted as honeydew.
The page also says nitrogen levels are usually higher in younger tissue than in older leaves. This helps explain why new shoots can be attractive to feeding insects. It also explains why the page warns that plants that are overfertilized, especially with nitrogen-based fertilizers, produce succulent growth that is more susceptible to plant-feeding insects. The page lists this as a general pattern for insects and mites rather than a leafhopper-specific result.
Where the leafhopper enters the leaf life cycle
The Hort Answers page gives some life-cycle detail for the potato leafhopper. The insect survives the winter in the Gulf States and is blown north in the spring. Once in Illinois, it goes through several generations in a growing season. Eggs are laid in cuts made along the veins on the underside of leaves, and also in the leaf petiole, which is the stalk that joins the leaf to the stem.
This timing matters because each generation can feed on new growth. The page does not give counts of generations or population sizes for a given garden, so the number of feeding cycles in any one season cannot be estimated from the sources.
Which plants are most often affected
The Hort Answers page lists the potato leafhopper as commonly found on red maple, wafer ash and burning bush. Its listed host plants include shrubs such as burning bush, and trees such as black locust, eastern redbud, red maple, sugar maple and thornless common honeylocust. The page rates the frequency of this pest as 5 on a scale from 1 for rare to 5 for annual, and the severity as 3 on a scale from 1 for very little damage to 5 for plants killed.
The severity rating is useful because it shows the page’s own view that the insect is common but usually not lethal. The rating is a scale used by the page, not a measured loss figure from a study.
How we chose these sources
This article uses two University of Illinois sources. The Hort Answers page is an extension guide for woody ornamental plants, and it describes the potato leafhopper’s feeding and symptoms. The Illinois IPM page, published April 7, 2005, explains the general feeding strategies of insects and mites on ornamental plants. Both were opened on 2026-10-27. The quotes and figures used here come from the text returned on that date.
The Hort Answers page also includes a management section that recommends insecticide treatment. This article does not repeat that advice. The question here is how the damage happens, not how to control the insect, so the control section is outside the scope of this explainer.
What we could not verify
The sources describe the feeding damage and the feeding method, but several questions remain open. The list below sets out the gaps.
What the sources do not say
- The sources do not name the toxins that leafhoppers release, and they do not describe how the toxins act on cells.
- The sources do not give leafhopper population counts for a garden, so the number of insects needed to cause visible damage cannot be estimated.
- The sources do not say how quickly leaf margins brown after feeding begins.
- The sources do not describe leafhopper damage on vegetables or herbs, because the Hort Answers page covers woody ornamentals.
- The sources do not confirm which species of leafhopper causes the hopperburn pattern on every host plant, beyond the potato leafhopper described on the page.
Frequently asked questions
Do leafhoppers chew holes in leaves?
No, according to the sources. Leafhoppers have piercing-sucking mouthparts, which they use to draw sap from the phloem. The IPM page says chewing insects are a different group that removes parts of leaves.
Why are the edges of the leaves turning brown?
The Hort Answers page says cells along the leaf edges die as a result of feeding, a condition it calls hopperburn. The page describes the edges as brown to black, with mottled leaves.
Will leafhopper feeding kill a tree?
The Hort Answers page says the damage does not cause serious damage to the health of the tree, but it reduces growth. The sources do not describe a case where leafhopper feeding killed a tree.
Why do leafhoppers feed on new shoots?
The IPM page says nitrogen levels are usually higher in younger tissue than in older leaves, and nitrogen is important for insect growth and reproduction. The page presents this as a general pattern for plant-feeding insects.
Does honeydew from leafhoppers harm leaves?
The IPM page describes honeydew as the excess sap that phloem-feeding insects excrete. The sources do not say that honeydew injures leaves, so this article does not make that claim.
Sources
- University of Illinois Extension, “Potato Leafhopper [Woody Ornamentals] (Empoasca fabae),” Hort Answers, https://web.extension.illinois.edu/hortanswers/detailProblem.cfm?PathogenID=88 (opened 2026-10-27)
- Illinois IPM, “Why and How Insects and Mites Feed on Your Plants and Flowers,” April 7, 2005, https://hyg.ipm.illinois.edu/pastpest/200501f.html (opened 2026-10-27)
