Japanese Beetle

Beetle control in the garden is a constant battle during the month of July. They appear in large numbers seeming to eat everything in the vegetable and flower garden. Daily scouting for damaged plants and adult beetles helps win the war against them and salvage the plants. The first line of defense is to identify the enemy. Just which beetle is eating the specific species and is it eating different plants is clue to controlling the different beetles.

The life cycle of all beetles have four stages: egg, larva, pupa and the adult beetle. Japanese, Asiatic garden and Oriental beetles lay eggs on the soil, where they hatch into white grubs and feed on plant roots. Pupation takes place under the soil, too. The adult beetles emerge after pupation, rising out of the soil in large numbers, looking to feed and mate, and then females will lay the next generation of eggs back on to the soil. There is one generation per year for most of the garden pest beetles. The most common garden pest beetles are also lawn pests as white grubs feeding on grass roots, but grubs can also be found in the vegetable and perennial gardens. Control grubs in the lawn by using conventional grub control. Organic options are parasitic nematodes and Bt galleria. Milky spore disease will only kill the Japanese beetle grubs. Bag traps to catch and contain adult beetles are available. They are specific to each variety of beetle and use a pheromone lure as an attractant. Place the trap away from the garden to keep the beetles from finding your plants. The organic options are a good choice for the soils in a vegetable garden. Other natural control measures are already in the environment. Tiphia wasps feed on the grub stage killing them. Hand pick beetles and drop into a container of soapy water. Attract birds to the garden to feed on the beetles by providing lots of perching spots with sticks and plant supports. Place a saucer of water or birdbath in the garden to invite them for a visit and meal. Floating row covers can be used to keep beetles off until plants flower and need pollinators to reach the flowers.

Japanese Beetle in hand

Japanese Beetle

Japanese beetles are cosmopolitan feeders. They have over 300 different host plants, but prefer some over others. Roses, sunflowers and beans are favorites of this metallic green and cooper colored winged beetle. The white grub is C-shaped with a tan head. The adults are active during the day and hide nearby at night.  Japanese beetles were brought to New Jersey accidentally in 1916 from Japan, and have spread up and down the eastern states. They are steadily moving westward. Japanese beetle feeding results in ragged foliage and distorted flowers. They are even known to chew on fruits and vegetables. Their damage can be extensive, especially when there is a large population.

Oriental beetle retry

Oriental Beetle

Oriental beetle is a mottled tan and dark brown beetle, active during the day also. They are native to Asia and are in many eastern states. They feed on a wide range of plants, especially the blossoms. Oriental beetles are most active in the afternoon and early evening before it gets dark.

Asiatic Garden Beetle 2

Asiatic Garden Beetle

Asiatic garden beetle are cinnamon brown in color and a little smaller than Japanese beetles. As the name implies, they are native to Asia, brought here around 1920. These beetles feed at night and hide in the soil below plants during the day. Scraping through the soil below night damaged plants will reveal the sleeping beetles. Flooding the area with a good soaking will also bring them to surface for capturing and killing.

Favorite plants for Asiatic garden beetles  are basil and roses.


Squash beetle and damage

Squash Beetle

Squash beetle eggs

Squash Beetle eggs.

Squash beetles are another big pest in my garden. They are yellowish-orange with 14 black spots. Their life cycle is different than the other three beetles mentioned above.  Adults overwinter in leaf litter and under loose tree bark, flying to the garden during the end of June. Squash beetles lay their eggs on the underside of squash, pumpkin and cucumber leaves and hatching out into a yellow, spiny larval grub to feed directly on the leaves. The adult and larval stage can destroy a crop quickly. Monitor daily for adults and turn over leaves to look for eggs which can be crushed or removed with sticky tape. I find clear packing tape and blue painters tape wrapped around my hand with sticky side facing out works well without ripping the leaves. Less eggs means less larva and adults eating the plants.

-Carol Quish

frass on leaf

Frass left on leaf after beetle feeding. Frass is insect poop!





Pest - Colorado Potato Beetle Adult, www.uwm.edu

Pest – Colorado Potato Beetle Adult, http://www.uwm.edu

Colorado potato beetle larvae, www.agriculture.purdue.edu larvae

Pest – Colorado potato beetle larvae, http://www.agriculture.purdue.edu larvae

Beetles are fascinating insects with a wide variety of colorful families and species. Some are beneficial, feeding on other insect, while other species are just plain pests. All beetles are in the order Coleoptera. Common among all adult beetles are two pair of wings, with front wings being thickened and leathery that completely cover the membranous hind wings. Adults have large compound eyes and chewing mouth parts.

Beneficial Predator as Adult - Eyed click beetle Photo by Pamm Cooper

Beneficial Predator as Adult – Eyed click beetle Photo by Pamm Cooper

Pest - Wireworms, maine.gov

Pest – Wireworms, maine.gov


Beetles have complete metamorphosis containing four life stages; egg, larva, pupa and adult beetle. Larvae have chewing mouth parts, and simple eyes which detect light, dark and movement, but cannot see as well as adult stage with the compound eyes. Different species of beetles differ in larval form. Some are c-shaped grubs with six legs, and others are wireworms with no legs. The common grubs found in the lawns will develop into beetles.

Pest - Japanese Beetle umass.edu

Pest – Japanese Beetle umass.edu

Pest - Japanese Beetle Adult

Pest – Japanese Beetle Adult

Control of all beetles can be achieved by hand picking adults and larval stages. Grubs in turfgrass are treated when grubs are newly hatched during the end of May through July by using Imidacloprid or Chlorotraniliprole as the active ingredient. Parasitic nematodes can be applied to lawns to infect the grubs, eating their insides so they never develop into adult beetles. Milky spore is a bacterial disease that affects only Japanese beetle grubs, although it has limited efficacy here in Connecticut.

In the vegetable garden, monitor known host plants by turning over leaves to look for eggs to crush them by hand. Insecticidal soap sprayed directly on any larvae will kill them by suffocation. Spinosad is an organic insecticide that will kill larval stages, too. Monitor for natural predators that would keep the pest population under control. Using broad spectrum insecticides will kill the good guys as well as the pests.

Carabid beetle Lebia grandis are voracious predators of Colorado potato beetle eggs and larvae. photo by Peggy Greb, extension.psu.edu

Carabid beetle Lebia grandis are voracious predators of Colorado potato beetle eggs and larvae. photo by Peggy Greb, extension.psu.edu

Colorado Potato Beetle Eggs, umass.edu

Colorado Potato Beetle Eggs, umass.edu


-Carol Quish




Years ago, when Organic Farming & Gardening magazine was printed in black and
white, and small enough to stuff into one’s pocketbook or jacket pocket to read
as time allowed, it was always filled with intriguing tips and commentaries for
growing better vegetables and controlling garden pests. I remember reading
about white geraniums being deadly to Japanese beetles. Not growing many
geraniums back then, I filed this piece of information somewhere in the back of
my mind until this past weekend.

While watering some pots of ‘Orange Appeal’ geraniums that I had started from seed
and strategically placed in an old blue, wooden wheelbarrow, I couldn’t help
noticing that there were belly up Japanese beetles nestled in the leaves! On
Saturday I just thought, how curious and flicked them off. A repeat performance
the next day triggered those latent memories and also brought back to mind a
more recent posting from the Agricultural Research Service (ARS).

Paralyzed Japanese beetle on geranium leaf

According to the ARS, the negative effect that geraniums have on Japanese beetles (an
obnoxious pest – at least here in New England) has been known since the 1920’s
but not until recently have scientists started exploring this relationship more
closely. It seems that within a half hour or so of nibbling on either the flowers
or (as I saw) leaves of the geranium (Pelargonium zonale), the beetles become paralyzed for about
24 hours. Had I known they were not dead, I would have finished them off. Under
laboratory conditions, the beetles generally will recover. In the wild,
however, they are often snacked upon by other critters since they don’t have
much of a chance of getting away in their paralyzed state.

An entomologist at the ARS, Chris Ranger, along with a scientist at Rutgers,
is working on developing a botanical insecticide from these paralytic compounds
which hopefully will be available sometime in the near future. Read more about “Geraniums
and Begonias: New Research on Old Garden Favorites”
in the March 2010 issue
of Agricultural Research magazine.

Not only are my few pots of geraniums helping to control the Japanese
beetles in my yard but as I hand pick them from my roses, 4 o’clocks, hollyhocks
and dahlias, I also have been noticing that a fair number of beetles have
little white spots on their green thoraxes. These are eggs of the Winsome fly.
The larvae will hatch and burrow into the beetle where it will begin feeding.
This apparently affects the beetle’s behavior and it will bury itself in the
soil where the larvae continues to feed and overwinters in the hollowed beetle
shell. The following year, an adult winsome fly emerges to continue its quest
to find more Japanese beetles to lay eggs on.

The white dots are eggs of the Winsome fly. Photo by Joan Allen, UConn

But enough of this backyard reality show! It’s summer1 The gardens are
glorious and, if you are looking to travel to the western part of
Massachusetts, do check out the house and grounds at The Mount, Edith Wharton’s
summer home.

The Mount, Lenox, MA

Edith Wharton was not only one of America’s greatest writers but
she also designed The Mount and the accompanying landscapes. There are 150
acres filled with mossy woodlands, meadows, tree-lined drives and walkways, her
restored greenhouse and formal gardens. The house which has in large part also been
restored can be toured as well and it is well worth a slow stroll through the
rooms which have many fascinating and little known facts about the life of
Edith Wharton and her great compassion and drive to help others during WWI and
later. Not only was she a great gardener, interior decorator, and writer but
she was also a great humanitarian. Take a step back in time and experience her
world in the early 1900’s.

One of the formal gardens at the Mount

Good gardening to you!