Asiatic Garden Beetle
Maladera castanea
Chewing Insects Moderate Risk 8-11 mm (adults)
📖 Description
The Asiatic garden beetle is an introduced pest from eastern Asia that has become established in the northeastern and midwestern United States. Unlike Japanese beetles, which feed during the day, Asiatic garden beetles are strictly nocturnal feeders, making their presence less obvious until significant damage has occurred. Both adults and larvae cause damage — adults feed on flowers, leaves, and fruit of over 100 plant species, while the white grub larvae feed on roots of grasses and garden plants. They are most active on warm, humid evenings from July through September.
⚠️ Symptoms to watch for
- Ragged holes and notches in flower petals and leaves,Skeletonization of leaves with only veins remaining,White grub damage to turf and plant roots,Adults found feeding at night or attracted to lights,Wilting plants due to root feeding by larvae
🩹 Treatment
- Hand-pick adults at night with a flashlight and drop into soapy water (organic),Apply beneficial nematodes (Heterorhabditis bacteriophora) to soil for grub control (organic),Use carbaryl or permethrin sprays for adult beetle control (chemical),Apply trichlorfon or imidacloprid as a soil drench for white grub control (chemical)
🌿 Organic treatments
- Hand-pick adults at night with a flashlight and drop into soapy water,Apply beneficial nematodes (Heterorhabditis bacteriophora) to soil for grub control
🧪 Chemical treatments
- Use carbaryl or permethrin sprays for adult beetle control,Apply trichlorfon or imidacloprid as a soil drench for white grub control
🛡️ Prevention
- Reduce outdoor lighting or use yellow bulbs less attractive to beetles,Maintain healthy turf to tolerate moderate grub feeding,Rotate garden crops to disrupt grub life cycle,Remove plant debris and weeds that shelter adults during the day
🪴 Affected plants
- Roses,Vegetables,Strawberries,Ornamental Flowers
🦋 Natural predators
- Birds,Skunks,Parasitic Wasps,Beneficial Nematodes
🌱 Host plants
- Rosa spp.,Fragaria × ananassa,Solanum lycopersicum,Phaseolus spp.
🔄 Lifecycle
- Asiatic garden beetles have one generation per year.
- They overwinter as grubs in the soil at depths of 15-30 cm.
- Grubs move upward in spring to feed on roots, then pupate in late June to early July.
- Adults emerge in July and August and are active for about two months.
- Females lay 20-40 eggs in the soil near host plants, and grubs hatch in about two weeks and feed until cold weather drives them deeper into the soil.
📅 Season
- Mid-Summer to Early Fall (adults); Spring and Fall (grubs)
🔎 Appearance
- Asiatic garden beetle adults are small, robust, chestnut-brown to reddish-brown beetles with a faint metallic sheen and a densely pubescent (hairy) body surface.
- Their wing covers appear slightly fuzzy and may be lighter brown at the margins.
- The larvae are typical white grubs — C-shaped, creamy white with a brown head capsule and three pairs of legs — reaching up to 25 mm at maturity.
- Adults are nocturnal and attracted to lights, often found in large numbers around porch and garden lights.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Moderate
🗺️ Geographic regions
- Eastern North America
- Japan
- China
- Korea
Have an Insect to Identify?
Upload or take a photo of an insect on your plant and our AI will identify it and recommend treatments.
📷 Diagnose from Image