Beetles

Pest Beetle Control With Natural Solutions

Beetle Larva - Larvae stage of the Japanese Beetle

Beetles are the largest group of insects (by number of species) with one-fourth of all insects belonging to this group. The order name is Coleoptera, which means "sheathed wing". All beetles have sheathes, called elytra, covering their wings; however, some beetles have the elytra fused and cannot fly. Not every member of Coleoptera is commonly called a beetle; some may have the name Borer (mainly wood borers), Weevil, chafer, or rootworm. Certain species of beetle are considered beneficial, like Ladybird Beetles (Hippodamia convergens, and play a key role in controlling other insects. Other examples of beneficial beetles are various ground beetles and Rove beetles.

Life Cycle:

The life cycle of all of beetles starts when a female lays eggs on or around the material that the larvae will consume. Eggs can be laid in the soil, on grain, on leaves, on seeds, or in plants themselves. Once the larvae emerge from the eggs, they feed voraciously. Mainly leaves will be consumed on the exterior of the plant while borers will feed on tissue inside the plant. Beetles with soil-dwelling larvae (eg. Japanese Beetles and rootworms) will feed on root systems of plants. The length of this stage may be as long as several years or until the plant is defoliated or otherwise weakened and dies. Eventually the larvae pupate and a mature adult beetle emerges, ready to eat, mate, and continue the beetle's life cycle.

Life Cycle of the Japanese Beetles and Grubs

Control of Pest Beetles:

Generally, control of pest beetles entails inspection of your plants and knowing what common beetle pests are in your area. Trap adults early in the season to identify and monitor pest populations before they become severe issues.

  • If you spot eggs laid on foliage or larvae actively feeding on foliage you can use a Neem Oil product to kill them before they hatch. Neem acts as a contact insecticide, so it has limited residual impact. Generalist Predators such as Ladybugs, Mantids, or Spined Soldier Bugs can also be released to control foliage feeding larvae.
  • If you see eggs or larvae that are on or within storage grains, you can use Diatomaceous Earth mixed with the grain; be sure to use food grade.

Controlling beetles is most effective when successful treatment of their immature stages is done. Manual removal of visible eggs and applications of Beneficial Nematodes to control larvae should be done early in the growing season before damage appears.

  • Nematode applications should be made when beetles with soil-dwelling larvae are present; although, nematodes can be injected into borer galleries when found.
    • Wood Borers leave an identifiable trace of wood shavings on the outside of tree bark; damage can be noticed by dark or discolored dead areas with sap and sawdust-like borings (frass) clinging to the bark or littering the ground. Since borers seek out trees that are injured or stressed, it is extremely important to maintain correct watering and mulching practices. Unfortunately, little can be done for the borer larvae inside the tree except to keep Fertilizing the tree. After the larvae emerge, you can treat the tree with Neem Oil, to kill any adults and the eggs they lay outside on the bark.
Beetles that have below-ground larvae (like the corn rootworm, Japanese Beetles, June bugs and a host of others who have a grub stage are successfully controlled with NemaSeek, Hb Beneficial Nematodes, and in the case of Japanese Beetle grubs, Milky Spore. Apply these products in the early fall or early spring while the grub stage is present underground.

The adult beetles that eat foliage – Japanese beetles, bean beetles, flea beetles – can be controlled with a number of different environmentally safe options, including Neem Oil products, Pyganic, Monterey Garden Insect Spray, or Bonide Garden Dust can be used to knockdown beetle populations. For more lasting control, Beauveria bassiana products can be applied to leaf surfaces and as a soil drench to infect and kill beetles at multiple life stages over time.

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