(Photo:  Beetle damage to Virginia Creeper)

Beetle Battles with Japanese, Cucumber, and Flea Beetles

Not all beetles are a problem. There are friends (e.g., rove & soldier beetles) and foes (e.g., Colorado Potato beetle). Three unfriendly ones common in any garden are the Japanese beetle, the cucumber beetle and the flea beetle, in descending order of importance.

Japanese Beetle

The Japanese beetle has favourite foods but will eat a wide variety of leaves and flowers when hungry. Infestations are common and the beetles eat all the soft parts of a leaf and leave the ribs and veins. My wife and I have lost over 120 feet of fence line Virginia creeper, many roses, zinnias, mallows, bean leaves (bush and pole), cucumber leaves, and soybean leaves, as well as the wild grape vine on my back fence and the leaves of my neighbour’s Linden tree. While I have named some plants we do not eat, these plants were used to provide a windbreak for our vegetables and composters, and food and shelter for birds, pollinators, and predator insects.

The Japanese beetles are active most of the summer months. They show a marked preference for warmth and tend to choose the sunny topmost leaves and flowers in the morning. They can be found on top of leaves and on the under sides, as well as tucked in between the petals of flowers. Later in the day they can be found most anywhere on plants, but exposure to the sun seems to be important in choosing a feeding site. Once they begin to feed, they release pheromones signaling other beetles in the neighbourhood that both feeding and mating should begin in earnest. And it does! Clusters of beetles show up and it becomes difficult to determine if they are feeding, mating or both at the same time – not that you really care! When ready to lay eggs, they stay near the food source and lay eggs in the soil or in the grass. The larvae live underground.

(Photo:  Beetle orgy on a rose)

Unfortunately, the best organic control method we have found is to hand pick the beetles and drown them in soapy water (e.g., used soapy dish water in a recycled yoghurt tub). While hand squashing the Colorado Potato beetle works well, squashing Japanese beetles is not advised because of the release of pheromones. A soapy spray has not proved very effective either, since the beetle is armor plated with a hard shell carapace and the spray must completely soak the adult beetle to block the breathing pores in its abdomen. Ours seemed to enjoy the shower!

Traps work, but there are drawbacks and I do not advise their use. The trap ($$) looks a bit like a WW2 bomb and has a pheromone patch attached to one of the yellow vanes. The container or bag at the bottom collects the beetles and can become quite full and very smelly. Plus, the pheromones bring in lots of beetles your garden might never have attracted. Some stop to snack on your plants on the way to the trap. On the other hand, you would be doing your neighbours a favour by collecting all their beetles as well as your own. If you use this trap, use it to lure the beetles away from your garden not to it! Place it away from all plants you wish to protect – about 50 feet – and clean it out often.

(Photo:  Japanese Beetle Trap with pheromone patch on one of the vanes)

To collect beetles, hold the container of soapy water about 3 inches directly under the beetle. At 4 or more inches, they will fly away or bounce off your hand or the rim of the container. The beetles are slow to react so knocking them into the container is not usually a problem. They just let go and drop three or so inches before flying. However, be prepared for a cluster of beetles all on one leaf. I have had as many as 7 on one pole bean leaf – two mating pairs and three wannabes. Two bounced off and got away to hide in the lower leaves.

(Photo:  20 minutes of collecting in soapy water)

If your infestation is a bad one, then there will be many beetle larvae in the soil or grass nearby. Our neighbourhood skunk comes by nightly and makes a lot of holes in the lawn to get at the beetle larvae. While the holes are unsightly, we accept it as free lawn aeration and insect control. You can purchase nematodes to add to your lawn to destroy the Japanese beetle larvae, but you will have to babysit the nematodes as they need moisture all summer to keep them well.

Another option is to take a holiday from growing some of the beetle’s favourite plants. We no longer have Virginia creeper or any roses, and our gardens do not have large numbers of any one kind of plant — another very good reason for biodiversification!

Cucumber Beetle

(Photo:  Cucumber beetles (left) and yellow sticky cards)

The cucumber beetle is smaller than the Japanese beetle and can be found in the flowers and on the leaves of cucumber and squash plants. They may also be carrying a plant virus. Naturally, they arrive in your garden to coincide with the blooming of theses plants. Unfortunately, they are awkward to get at in the deep throats of some flowers, so hand picking or squashing them is a challenge. Drowning them in soapy water is effective if you can get at them. A hand-held vacuum with a crevice tool can help, but use the lowest suction you can arrange. A soap spray has to hit them directly and soak them, and it must be rinsed off the plant after 10 minutes. A garlic spray (no need to rinse) sprayed into the flowers and on the leaves can help discourage them. Yellow sticky cards also work, but they catch many different insects as the colour yellow is popular with garden insects; you will have noticed that many vegetable plants and flowers have yellow petals or yellow centres.

Flea Beetle

(Photos:  Flea beetle and Flea beetle damage)

The flea beetle is very small and quick to escape. Eggplant seems to be a favourite food but other plants can be affected. This beetle leaves pin holes in the leaves and most plants can withstand a few flea beetles unless there is an infestation. Drowning these beetles is not really an option. Yellow sticky cards are the best bet if you find it necessary to reduce their numbers. Otherwise just monitoring their activity and letting the plant deal with the attack may be enough.

If you expect an infestation because of the previous year’s activity, then protect the plants with row covers. Plants already infested can also be covered to prevent the beetles relocating. Use yellow sticky cards daily and soap spray (+ rinse) every three days until the problem is resolved. Remember that the row cover will have to be removed for a couple of hours daily if the plants need pollinating.

(Photo:  Yellow sticky cards used in a greenhouse operation).

If you use a sprayer, note that oil and plastic attract each other and cling. Three inexpensive sprayers are a dollar store purchase, a brass pump (sprays on both the push and the pull stroke) to which you add a recycled 2 litre pop bottle, and a do-it-yourself sprayer that uses a recycled pistol and a recycled bottle – only the tube is purchased. The sprayers with tubes allow the pistol to be manipulated in any direction without tipping the bottle. The brass pump is excellent and reaches farther and higher for tall plants; however, the bottle must remain upright at all times to keep the syphon straw in the liquid.

(Photos:  Dollar store, brass pump, and DIY sprayer)

As you might expect, the first line of defense in any organic garden is threefold:

  • Keep the garden soil and plants healthy with compost, water, and mulch (Note: some healthy plants increase toxins in their leaves to combat bug attacks; weakened plants will attract feeding insects – it is part of nature’s design: survival of the fittest).
  • Check the plants often for thirst, nutrient deficiencies, or damage from wind, bacteria, fungi, viruses, insects, animals, or people.
  • Start treatment as soon as a problem develops.
  • Add a water feature, a bird feeder, a bug hotel, and bug restaurants all can help attract birds, critters, and predator insects to assist with organic insect control. They too are a part of biodiversity.

Plants do have their own defenses, but at times they need an intervention to help them cope.

Protect those plants!