japanese beetles life cycle control organic gardening

Japanese Beetles are an invasive insect that first arrived in the Midwestern United States in the 1990s and they are, unfortunately, likely here to stay. The larvae/grubs feed on plant roots and the adults skeletonize plant foliage. Damage usually becomes apparent in mid to late summer, when the adults are active and feeding above ground. They are easily identified by their metallic green color and their tendency to gather in large numbers on favored plants.

Due to their life cycle and their mobility as adults (adults can fly up to a mile), Japanese Beetles can be challenging to control. Damage to plants can be minimized, however, by utilizing a multi-pronged approach to control. The first and easiest way to discourage Japanese Beetles is to select plants for your landscape that they are not as likely to attack, and to avoid those that they prefer.

A partial list of plants that are resistant to Japanese Beetle damage follows:

Resistant Perennials

  • Yarrow (Achillea)
  • Ornamental Onion (Allium)
  • Butterfly Weed (Asclepias)
  • Aster (Aster)
  • Masterwort (Astrantia)
  • False Indigo (Baptisia)
  • Turtlehead (Chelone)
  • Coreopsis (Coreopsis)
  • Dianthus (Dianthus)
  • Bleeding Heart (Dicentra)
  • Ferns (Ferns)
  • Blanketflower (Gaillardia)
  • Prairie Smoke (Geum)
  • Baby’s Breath (Gypsophila)
  • English Ivy (Hedera)
  • Lenten & Christmas Rose (Helleborus)
  • Daylily (Hemerocallis)
  • Coralbells (Heuchera)
  • Hosta (Hosta)
  • Iris (Iris)
  • Gayfeather (Liatris) – pictured
  • Lilies (Lilium)
  • Beebalm (Monarda)
  • Catmint (Nepeta)
  • Spurge (Pachysandra)
  • Poppy (Papaver)
  • Obedient Plant (Physostegia)
  • Black-Eyed Susan (Rudbeckia)
  • Sedum (Sedum)
  • Toad Lily (Tricyrtis)
  • Veronica (Veronica)
japanese beetles control perennials organic gardening johnson's gardens cedarburg

Resistant Annuals

  • Ageratum
  • Snapdragons
  • Begonia
  • Cosmos
  • Impatiens
  • Ornamental Kale
  • Lantana – pictured
  • Nasturtium
  • Nicotiana
  • Ornamental Pepper
  • Pansy
  • Petunia
  • Portulaca
  • Verbena
japanese beetles control annuals organic gardening johnson's gardens cedarburg

Resistant Trees & Shrubs

  • Arborvitae (Thuja)
  • Boxwood (Buxus)
  • Burning bush (Euonymous)
  • Dogwood (Cornus)
  • Lilac (Syringa)
  • Forsythia (Forsythia)
  • Juniper (Juniperus)
  • Magnolia (Magnolia)
  • Pine (Pinus)
  • Red Oak (Quercus)
  • Redbud (Cercis) – pictured
  • Red Maple (Acer)
  • Spruce (Picea)
  • Tulip Tree (Liriodendron)
  • Yew (Taxus)
japanese beetles control trees organic gardening johnson's gardens cedarburg

Resistant Perennials

japanese beetles control perennials organic gardening johnson's gardens cedarburg
  • Yarrow (Achillea)
  • Ornamental Onion (Allium)
  • Butterfly Weed (Asclepias)
  • Aster (Aster)
  • Masterwort (Astrantia)
  • False Indigo (Baptisia)
  • Turtlehead (Chelone)
  • Coreopsis (Coreopsis)
  • Dianthus (Dianthus)
  • Bleeding Heart (Dicentra)
  • Ferns (Ferns)
  • Blanketflower (Gaillardia)
  • Prairie Smoke (Geum)
  • Baby’s Breath (Gypsophila)
  • English Ivy (Hedera)
  • Lenten & Christmas Rose (Helleborus)
  • Daylily (Hemerocallis)
  • Coralbells (Heuchera)
  • Hosta (Hosta)
  • Iris (Iris)
  • Gayfeather (Liatris) – pictured
  • Lilies (Lilium)
  • Beebalm (Monarda)
  • Catmint (Nepeta)
  • Spurge (Pachysandra)
  • Poppy (Papaver)
  • Obedient Plant (Physostegia)
  • Black-Eyed Susan (Rudbeckia)
  • Sedum (Sedum)
  • Toad Lily (Tricyrtis)
  • Veronica (Veronica)

Resistant Annuals

japanese beetles control annuals organic gardening johnson's gardens cedarburg
  • Ageratum
  • Snapdragons
  • Begonia
  • Cosmos
  • Impatiens
  • Ornamental Kale
  • Lantana
  • Nasturtium
  • Nicotiana
  • Ornamental Pepper
  • Pansy
  • Petunia
  • Portulaca
  • Verbena

Resistant Trees & Shrubs

japanese beetles control trees organic gardening johnson's gardens cedarburg
  • Arborvitae (Thuja)
  • Boxwood (Buxus)
  • Burning bush (Euonymous)
  • Dogwood (Cornus)
  • Lilac (Syringa)
  • Forsythia (Forsythia)
  • Juniper (Juniperus)
  • Magnolia (Magnolia)
  • Pine (Pinus)
  • Red Oak (Quercus)
  • Redbud (Cercis) – pictured
  • Red Maple (Acer)
  • Spruce (Picea)
  • Tulip Tree (Liriodendron)
  • Yew (Taxus)

Plants Vulnerable to Japanese Beetles

Vulnerable Perennials

  • Hollyhocks (Althea)
  • Japanese Anemone (Anemone)
  • Joe Pye Weed (Eupatorium)
  • Hardy Hibiscus (Hibiscus)
  • Evening Primrose (Oenothera)
  • Virginia Creeper & Boston Ivy (Parthenossisus)

Vulnerable Annuals

  • Cannas
  • Dahlia
  • Hibiscus
  • Marigolds
  • Morning Glories
  • Zinnias

Vulnerable Trees & Shrubs

  • Rose (Rosa)
  • Birch (Betula)
  • Rose-of-Sharon (Hibiscus)
  • Linden/Basswood (Tilia)
  • Apricot, Cherry, Peach, and Plum (Prunus)
  • Crabapple & Apple (Malus)
  • Japanese Maple (Acer)
  • Raspberry (Rubus)

Organic Control for Adult Beetles

The Bucket Method

If you’re not squeamish, you can dispose of a large number of Japanese Beetles by simply shaking them off the plant and into a bucket of soapy water (they are slow moving and usually distracted by doing ….well, if you’ve ever seen them on your plants you KNOW what they’re doing, ALL OF THE TIME).

Beetle Bags

These are capture bags that come with a scent lure to attract, trap and kill Japanese Beetles. Placement of bags is critical! These bags should be placed at least 30’-40’ away from the plant that is being attacked. The idea is to lure them away from the desired plant and trap/kill them. Placing a bucket of soapy water under the bag will increase your numbers removed as these guys are clumsy and will often fly towards the lure, bump into the bag, and fall to the ground (into your waiting bucket).

Repellents

We carry an effective Japanese Beetle repellent that is completely natural and safe (Bobbex Rose). During peak beetle season it will need to be re-applied every few days.

Organic Insecticides

  • Bonide Japanese Beetle Killer is an organic broad spectrum contact insecticide that is made from the flowers of Chrysanthemums. It will kill Japanese Beetles when sprayed on them but will need to be re-applied as new populations move into the garden.
  • Bonide’s Bon-Neem contains the same natural insecticide as the above but also contains Neem Oil. Neem Oli is derived from the seed of a tropical tree and acts as an anti-feedant in addition to having repellent qualities.
  • Captain Jack’s Deadbug is a highly effective organic insecticide that acts on contact as well as being a stomach poison.

Chemical Control for Adult Beetles

Bonide’s Eight is a powerful chemical insecticide that will kill Japanese Beetles on contact and has a residual effect as well.

Bonide’s Rose Shield offers three-way control, both contact and systemic insect control plus systemic disease control. It penetrates the plant tissue and provides control from insect damage for up to 30 days.

Bonide’s Annual Tree & Shrub Insect Control and Bayer Rose & Flower Care contain a systemic insecticide. These are applied to the base of the plant and taken up through the vascular system of the plant to provide protection for the entire growing season. Best applied in late fall or earliest spring so that it is available to the plant as the sap is most active in the spring. This is often the choice for protecting individual specimen plants that are being defoliated (note: Illegal to apply to members of the genus Tilia, which includes Linden Trees & Basswood).

Organic Control for Beetle Grubs

Milky Spore Disease is a disease caused by a bacteria that targets Japanese Beetle grubs but  is not harmful to beneficial insects, birds, bees, pets, or people. August is the ideal time for application of Milky Spore to the lawn as this is when the small grubs are feeding near the soil surface and are most vulnerable to infection. The bacteria then reproduces inside the grub, kills them, and after they die their bodies release more bacteria into the soil. By this means the milky spore disease spreads and will, within three to four years, completely colonize the lawn so that grubs can no longer survive there.

Cultural Practices. Japanese Beetles prefer to lay their eggs in short turf so cutting your lawn high (over 2″) may reduce the number of eggs laid. Beetle eggs need moisture to hatch so keeping your lawn dry in the month of August may reduce the number of eggs that hatch.

Chemical Control for Beetle Grubs

Bonide’s Grub Beater contains a systemic insecticide but is directed at the immature/grub stage of the Japanese Beetle’s life cycle. This product is applied to the lawn and effectively kills the beetle larvae/grub as they feed on the roots of lawn grasses. Due to the residual activity, application can be made before or during egg laying season and will remain effective for the entire season.