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Beetles

Pest Beetle Control With Natural Solutions

Beetles are the largest group of insects (by number of species). One-fourth of all insects belong to this group. The order name is Coleoptera, which means “sheathed wing”. All beetles have these 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; it may have the name borer (mainly wood borers), weevil, chafer, or rootworm. Beetles can be found everywhere except in the ocean and the polar regions. Certain species play a key role in controlling other insects; these are considered beneficial. Examples of beneficial beetles are the ladybird beetle, Hippodamia convergens, plus various ground beetles and rove beetles.

Certain other species of beetles are considered pests, attacking a variety of plants. The life cycle of all of these starts when a female lays eggs on the material that the larvae will consume. For instance, eggs are placed on grain if it is a grain beetle; on leaves if it is the Colorado potato beetle; on seeds, if a seed borer; or buried in the item, if a carrot weevil. Once the larvae emerge from the eggs, they eat voraciously. The outside of the plant, mainly the leaves, will be consumed; the damage may be done internally – in the case of borers, damage is done inside the stem or under the bark of trees; or with rootworms, the roots of  the corn plant are consumed. 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 will pupate and a mature adult beetle will emerge, ready to eat, mate, and keep the cycle going. Many adult beetles do just as much damage as the larvae; others do not – the danger is the number of eggs they lay to keep the cycle going.

Control of Pest Beetles

Generally, control of pest beetles entails inspection of your plants and knowing what common beetle pests are in your area. It is easier to start with beetles that have above-ground eggs and larvae.

  • If you spot eggs laid on foliage, you can use a Neem oil product to kill them before they hatch; if you spot larvae devouring foliage (e.g. asparagus beetle larvae), you can use Neem oil again, or you can use generalist predators such as ladybugs, mantids, or spined soldier bugs to eat foliage feeding larvae.
  • If you see eggs or larvae that are on or within storage grains, you may wish to use Diatomaceous Earth mixed with the grain; our 50 lb bag is food grade.
  • 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 can successfully attack only trees that are injured or stressed, it is extremely important to maintain correct watering; mulching also helps – consider using ARBICO Compost as mulch. Unfortunately, little can be done for the borer larvae inside the tree except to keep fertilizing (feeding) 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 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, plus predators such as Praying Mantids and insectivorous birds can make short work of an infestation that is damaging your crop or garden. 

Beetles Damaging Flowers - Organic Beetle Control
Adult Japanese Beetles damaging flower petals.
Beetle Larva - Larvae stage of the Japanese Beetle
White grub - the larva stage of Japanese Beetles. Can be as damaging or more damaging than the adults.
Life Cycle of the Japanese Beetles and Grubs
Life Cycle of the Japanese Beetle

Related Article: Japanese Beetles - Beetle Mania.