Yes. Invasive Asian beetles such as the Japanese beetle and the Asian longhorned beetle feed on leaves, flowers and even roots, causing serious harm to plants, trees and turf.

 

What Are Asian Beetles?

 

Asian beetles are non-native insects accidentally introduced from parts of Asia. Common examples include:

• Japanese beetle (Popillia japonica): a shiny metallic green adult about ½ inch long that feeds on over 300 plant species.
• Asian longhorned beetle (Anoplophora glabripennis): a large black-and-white spotted beetle whose larvae tunnel inside trees.
• Oriental beetle (Exomala orientalis): resembles the Japanese beetle but is less metallic and mainly damages turfgrass roots.

 

How Do Asian Beetles Harm Plants?

 

These beetles damage plants through their feeding and life cycle stages:

• Adult feeding: Chew on leaf tissue between the veins, leaving a lace-like “skeletonized” appearance. Flowers, fruit and young shoots can be completely consumed.
• Larval (grub) stage: Lives in soil and feeds on roots, reducing a plant’s ability to take up water and nutrients. Grub damage leads to wilted, yellowing or dead patches in lawns and weakened garden plants.
• Tunneling (longhorned beetle): Larvae of the Asian longhorned beetle bore deep galleries in wood, disrupting nutrient flow and eventually killing branches or entire trees.

 

Signs of Infestation

 

• Leaves with holes or a lace-like skeleton pattern.
• Flowers or fruit chewed or completely stripped away.
• Brown, thinning patches in lawns where grubs have eaten roots.
• Bark exit holes (roughly the size of a dime) and sawdust-like frass on tree trunks or at the base.
• Wilting or dieback of branches even when foliage is otherwise healthy.
• Gardeners in Nashua sometimes first spot Japanese beetles by the noisy chewing on rose blooms or grape leaves in summer evenings.

 

Prevention and Control Strategies

 

• Manual removal: Handpick feeding adults early in the morning when they are sluggish. Drop them into soapy water to kill.
• Barriers and covers: Use row covers on vulnerable crops to keep beetles away during peak emergence.
• Traps: Pheromone traps attract beetles but must be placed far from prized plants to avoid concentrating pests nearby.
• Biological controls:
  • Beneficial nematodes or milky spore (Bacillus popilliae) applied to soil to attack grubs.
  • Encourage birds and insect predators like tachinid flies, which parasitize Japanese beetle grubs.
• Chemical treatments:
  • Contact insecticides for quick knockdown of adults on foliage.
  • Systemic insecticides for trees to protect from borers like the Asian longhorned beetle.
• Integrated Pest Management (IPM): Combine monitoring, cultural, biological and, if needed, chemical controls for the most effective, environmentally sensitive approach.

By recognizing the signs early and using multiple control methods, you can protect your garden, lawn and trees from destructive Asian beetles.