8 Invasive Insects Attacking Kansas Gardens, Crops, and Trees

Kansas ash trees are dying at an alarming rate—not from disease or drought, but from tiny metallic-green beetles that arrived from Asia. Since 2012, these invaders have spread to 18 counties, and they’re just one of several non-native insects reshaping the state’s agricultural and natural landscapes.

From backyard gardens to commercial farms and urban forests, invasive insects in Kansas are causing millions of dollars in damage while threatening native ecosystems. You’ll need to recognize these destructive species and understand their impact on your property, whether you’re protecting a single tree or managing hundreds of acres.

1. Emerald Ash Borer

The emerald ash borer (Agrilus planipennis) stands as one of Kansas’s most destructive invasive insects, targeting ash trees with devastating efficiency. This metallic-green beetle native to East Asia first appeared in North America in 2002 and reached Wyandotte County, Kansas, in 2012. Since then, it has expanded to 18 counties across the state, killing millions of ash trees and forcing costly removal of thousands more.

Key Insight: Kansas is home to an estimated 65 million ash trees, with approximately 93% found on privately-owned forest land, making property owners the primary stakeholders in managing this threat.

Adult beetles measure just half an inch long with distinctive metallic emerald-green bodies and darker, metallic green wings. Their larvae bore into ash trees and feed on the inner bark, disrupting the tree’s ability to transport water and nutrients. Infested trees show thinning canopies, D-shaped exit holes in the bark, and increased woodpecker activity as birds feed on the larvae beneath the bark.

The Kansas Department of Agriculture lifted its quarantine on emerald ash borer movement in March 2021, shifting resources toward education, outreach, and biological control rather than containment. Three parasitic biological control agents are now being released throughout Kansas to help manage populations naturally. Property owners in affected counties should assess which ash trees they wish to protect, as untreated specimens will likely succumb to future infestations.

Dead ash trees create gaps in forest canopies that provide opportunities for other invasive species to establish. Native species that depend on ash for habitat or food also face negative impacts. The Kansas Forest Service recommends that landowners contact certified arborists for guidance on protecting valuable ash trees or safely removing infested ones before they become hazardous.

2. Japanese Beetle

Japanese beetles (Popillia japonica) emerge from Kansas soil each summer with voracious appetites, feeding on more than 300 different plant species. These bright-green invasive insects attack native plants and valuable cash crops including corn, soybeans, roses, American elm, willow, Virginia creeper, linden, and crabapple.

Adult beetles measure approximately half an inch long with metallic green bodies and copper-brown wing covers. Five distinctive white hair tufts along each side of their abdomen and two additional tufts at the tip help distinguish them from native species. When they emerge in early summer, they immediately begin feeding and mating, with females laying eggs in soil throughout their three-month active period.

Pro Tip: Japanese beetles spend most of their annual life cycle as white, C-shaped grubs beneath the ground, feeding on grass roots and plant roots. They retreat deeper into soil as temperatures drop, emerging the following summer to repeat the cycle.

Professor Raymond Cloyd at Kansas State University explains that when beetles are active for three months, they consume everything they can reach. Their feeding creates a distinctive skeletonized appearance on leaves, where only the veins remain after beetles devour the tissue between them. This damage weakens plants, reduces crop yields, and can kill younger or more vulnerable specimens.

Control methods include hand-picking beetles into soapy water or rubbing alcohol, which also reduces pheromone signals that attract additional beetles to the area. Some Kansas residents feed collected beetles to geese and ducks as a natural disposal method. Insecticides applied to plants during summer or to soil before grubs emerge offer chemical control options. Ground applications targeting grubs before they emerge as adults can reduce future populations more effectively than treating adult beetles.

3. Brown Marmorated Stink Bug

The brown marmorated stink bug (Halyomorpha halys) has established populations across Kansas, threatening both agricultural crops and home comfort. This shield-shaped invasive insect from East Asia feeds on fruits, vegetables, and ornamental plants while seeking indoor shelter during colder months.

Adults measure roughly five-eighths of an inch long with mottled brown coloring that provides effective camouflage on tree bark and plant stems. Distinctive white bands on their antennae and alternating light and dark bands along the outer edges of their abdomen help identify this species. Their shield-shaped body and the characteristic foul odor they emit when threatened or crushed make them unmistakable once you encounter them.

These stink bugs use their piercing-sucking mouthparts to extract plant fluids, leaving behind dimpled or discolored areas on fruits and vegetables. On crops like tomatoes, peppers, corn, and soybeans, their feeding causes scarring, deformation, and reduced marketability. Ornamental plants suffer stunted growth and leaf damage from repeated feeding.

As temperatures decline in late summer and fall, brown marmorated stink bugs aggregate on the southern and western sides of buildings, seeking entry through cracks, gaps, and openings. Once inside, they enter a dormant state called diapause in attics, wall voids, and other protected spaces. They don’t reproduce indoors or cause structural damage, but large numbers create nuisance problems when they emerge on warm winter days or in spring.

Prevention focuses on sealing entry points before the fall invasion period. Caulk cracks around windows and doors, repair damaged screens, and install door sweeps to block access. If stink bugs enter your home, vacuum them carefully and release them outside rather than crushing them, which releases their defensive odor and can stain surfaces.

4. Spotted Lanternfly

Kansas detected its first spotted lanternfly (Lycorma delicatula) when a 4-H student in Thomas County found one in western Kansas and included it in an entomology display, triggering state and federal investigations. This invasive planthopper from Asia threatens vineyards, orchards, and hardwood forests while spreading rapidly across multiple states.

Adult spotted lanternflies display striking coloration with gray forewings featuring black spots and bright red hindwings with black spots and white bands. They measure approximately one inch long and half an inch wide. Nymphs progress through four stages, starting as black with white spots, then developing red patches before reaching adult form. All life stages feed by piercing plant tissue and extracting sap.

Common Mistake: Spotted lanternflies are often confused with native moths, but their behavior gives them away—they hop and jump short distances rather than flying long distances like most moths.

Their preferred host is tree of heaven (Ailanthus altissima), another invasive species, but they also feed on grapevines, fruit trees, hops, hardwoods, and over 70 other plant species. Heavy feeding causes oozing wounds on tree trunks and branches, with honeydew excretion promoting sooty mold growth that interferes with photosynthesis. Economic impacts are particularly severe for grape growers and fruit producers.

Females lay egg masses containing 30 to 50 eggs on smooth surfaces including trees, outdoor furniture, vehicles, and equipment. These egg masses resemble gray mud splotches and remain viable through winter. Accidentally transporting egg masses on vehicles or equipment contributes to the insect’s rapid spread to new areas.

Kansas residents should report any spotted lanternfly sightings immediately to the Kansas Department of Agriculture. Early detection remains critical for containing this threat before populations explode. If you discover egg masses on your property, scrape them off into bags with rubbing alcohol or hand sanitizer to kill the eggs before disposal.

5. Asian Lady Beetle

Asian lady beetles (Harmonia axyridis) invade Kansas homes by the hundreds or thousands each fall, earning their nickname as the “Halloween Beetle” for their October invasions. While these orange beetles benefit agriculture by consuming aphids and other crop pests, their overwhelming presence in homes creates significant nuisance problems.

Adults measure about one-quarter inch long with coloring ranging from pale yellow to deep orange or red. Black spots vary from none to nineteen, with some individuals displaying no spots at all. The most reliable identification feature is the distinctive black “W” or “M” marking on the white area behind their head, which no native lady beetle possesses.

Originally introduced to North America decades ago as biological control agents, Asian lady beetles excel at controlling aphid populations, particularly soybean aphids that threaten Kansas agriculture. Both adults and larvae consume aphids, scale insects, and other soft-bodied pests, making them valuable allies during growing season. Professor Raymond Cloyd at Kansas State University emphasizes their effectiveness as predators, noting their substantial contribution to pest management.

Important Note: Kansas lacks the natural cliff habitat where Asian lady beetles typically overwinter in their native range. As temperatures drop, they instead seek protected spaces in buildings, congregating on south-facing walls before entering through cracks and gaps.

Problems arise when beetles aggregate indoors for winter. They don’t reproduce, feed, or cause structural damage inside homes, but their sheer numbers become overwhelming. Crushed beetles release a yellow, foul-smelling fluid that stains furniture, curtains, and clothing. Dead beetles behind walls can create dust that irritates some people. Their defensive secretions may also cause minor skin irritation or allergic reactions in sensitive individuals.

Managing Asian lady beetle invasions requires prevention rather than elimination. Before fall arrives, seal cracks around windows, doors, utility penetrations, and foundation. Install or repair window screens and add door sweeps. If beetles enter despite precautions, vacuum them carefully and empty the vacuum outdoors. Avoid crushing them due to staining potential. Cloyd recommends tolerance when possible, as the beetles eventually leave in spring and provide valuable pest control once they return outdoors.

6. European Corn Borer

The European corn borer (Ostrinia nubilalis) ranks among the most economically damaging invasive insects affecting Kansas agriculture, targeting corn, sorghum, peppers, potatoes, and numerous other crops. This moth species arrived in North America over a century ago and has cost farmers billions of dollars in crop losses and control expenses.

Adult moths display subtle coloring that aids in survival, with females showing yellowish-tan wings marked with irregular dark bands and males appearing slightly darker overall. Both sexes measure about three-quarters of an inch across when wings are spread. The larvae cause the actual damage—pale caterpillars with brown heads and distinctive dark spots on each segment, reaching one inch long when fully grown.

Female moths lay cream-colored eggs in clusters of 15 to 30 on the undersides of corn leaves. After hatching, young larvae feed on leaves, tassels, and silks before boring into stalks, ears, and other plant parts. This tunneling disrupts nutrient and water transport, weakens stalks (causing them to break in wind), and provides entry points for fungi and bacteria. Multiple generations occur each year, with timing depending on temperature and location within Kansas.

Corn borer larvae overwinter inside crop residue, particularly corn stalks, stubble, and plant debris left in fields. This overwintering behavior makes crop residue management a critical control strategy. Tillage that buries or shreds crop residue eliminates overwintering sites and significantly reduces spring populations. Planting Bt corn varieties that produce proteins toxic to European corn borer larvae has revolutionized management, reducing insecticide applications while maintaining yields.

Scouting fields regularly during the growing season helps determine when corn borer pressure justifies treatment. Look for larvae, feeding damage on leaves, holes in stalks, or sawdust-like frass near entry holes. Biological control agents including parasitic wasps and insect-pathogenic fungi provide some natural population suppression. Crop rotation, planting date adjustments to avoid peak moth flights, and maintaining beneficial insect habitat all contribute to integrated pest management approaches.

7. Russian Wheat Aphid

The Russian wheat aphid (Diuraphis noxia) poses a severe threat to Kansas wheat and barley production, with feeding damage capable of decimating entire fields. This pale green to white aphid arrived in the United States in 1986 and quickly spread across the Great Plains, causing millions of dollars in annual losses.

These tiny invasive insects measure only one-sixteenth inch long, making them difficult to spot without close inspection. Unlike many aphid species, Russian wheat aphids lack cornicles (the small tubes projecting from the rear of most aphids), which aids in identification. Their pale coloring helps them blend with plant tissue, and they typically feed in leaf whorls and on developing heads where they’re protected from environmental exposure.

Pro Tip: Russian wheat aphid damage creates distinctive symptoms that set it apart from other aphid species—look for white to purple longitudinal streaks on leaves, flat leaf blades that fail to unfurl properly, and heads that remain trapped within the boot or emerge twisted and distorted.

Feeding by Russian wheat aphids injects toxic saliva that disrupts plant growth beyond simple nutrient extraction. Infested plants show stunted growth, reduced tillering, and leaves that roll lengthwise into tight tubes. Heavy infestations prevent heads from emerging or cause them to be sterile. Yield losses can reach 80% or higher in severely damaged fields.

These aphids reproduce rapidly, with females giving birth to live young without mating during most of the year. A single aphid can produce 80 offspring in three weeks under favorable conditions, leading to explosive population growth. They remain active year-round in Kansas, with populations building on volunteer wheat and winter wheat throughout fall and winter.

Management relies heavily on resistant wheat varieties that tolerate or resist Russian wheat aphid feeding. Several resistant varieties are available for Kansas growers, though aphids can adapt to overcome resistance over time. Regular field monitoring during fall and spring allows early detection when populations are small and easier to control. Natural enemies including lady beetles, lacewings, and parasitic wasps provide some biological control. Insecticides offer emergency control but must be applied before aphid numbers explode and before damage becomes irreversible.

8. Alfalfa Weevil

The alfalfa weevil (Hypera postica) attacks Kansas alfalfa fields each spring, with larval feeding capable of destroying first cuttings if populations aren’t managed effectively. This European native established throughout the United States decades ago and remains a primary pest concern for alfalfa producers.

Adult weevils measure about three-sixteenths inch long with brown bodies and a distinctive dark stripe running down the back. Their snouts extend forward, characteristic of the weevil family. Adults overwinter in field edges, crop residue, and protected areas, becoming active in early spring when temperatures warm. Females lay eggs inside alfalfa stems, with each female producing several hundred eggs over her lifetime.

Larvae cause the majority of damage to alfalfa crops. These legless, green caterpillars with white stripes down their backs and black heads feed on growing alfalfa tips, preferring the tender new growth. Early damage appears as small pinholes in leaves, but as larvae grow, they consume more tissue, creating a skeletonized appearance where only leaf veins remain. Severe infestations give fields a frosted or silver appearance from a distance due to extensive feeding damage.

Timing first cutting earlier than usual can be an effective management strategy when weevil populations are high. This removes larvae with the harvested hay and disrupts their life cycle.

However, cutting too early may sacrifice yield and forage quality. Scout fields weekly in spring using a sweep net, with action thresholds depending on alfalfa growth stage and market conditions.

Natural enemies including parasitic wasps, predatory beetles, and insect diseases help suppress alfalfa weevil populations. Preserving beneficial insects by avoiding broad-spectrum insecticides when possible and maintaining field border habitat supports biological control.

Chemical control becomes necessary when populations exceed economic thresholds, with several effective insecticides available. Applications work best against young larvae before they cause extensive damage and before they drop to the ground to pupate.