They are a pest that is sweeping across neighbourhoods, devastating gardens, shrubs, trees and field crops without mercy. A relatively new introduction to our area originating from Japan (big surprise), landing in North America a century ago. While they are natural controlled in Japan, the lack of natural predators here has made them a major pest. Japanese Beetles are especially attracted to plants like raspberry, canna, roses and maples but have been known to feast on over 300 plant spices (so clearly it’s not a selective eater).

Japanese beetles are an easy pest to identify in the garden as they make themselves known immediately. When present you can spot them as they have bright metallic green heads with metallic copper coloured bodies. If none are visible the skeletonizing of the leaves they feed on are a dead giveaway. These beetles seem to not enjoy the veins as they feed around them leaving the distinct damage in their wake.

This frustrating insect is a hard one to control for a couple reasons, first is a lack of ‘quick and easy’ option to apply and second is the physical structure of beetle pests. Their hard shell is thick and provides protection from traditional options that can penetrate thinner pest coatings. That said there are still things that gardeners can do to fight these nasty bugs and thwart their effect to destroy your beautiful gardens!

Japanese Beetle Traps

  • A trap using pheromones to attract the insects and a sack to catch them when they clumsily fly into the trap (Japanese beetles are poor fliers). Proven to be highly effective in attracting the beetles (maybe too much so).
  • Studies show the traps often attract more beetles than they can trap which is why we at Heeman’s do not endorse the use of these traps.
  • For gardeners driven mad by the beetles, we recommend you place the traps far away from your garden or ‘hot spots’ to draw the beetles away from your treasured plants. Be sure to empty the traps daily (or as often as possible) as they can only hold 10-15 beetles.
  • Unfriendly neighbours yards (kidding, sort of)¬†or the far end of your property make great homes for your traps.

Soapy Water

  • Grab a bucket and fill it with soapy water, then hand pick or shake the bugs into the bucket to kill them. You can leave the dead beetles beside your plant to scare off any future munchers.
  • Japanese beetles are sluggish and sleepy in the early morning and their iron like grips are often very relaxed making them easy to shake off. They are also less likely to take flight when shaken off in the early morning and more likely to land in your soapy water.
  • Alternatively, mix soap, water, garlic powder, and cayenne pepper in a spray bottle and apply it to your plants. These ingredients change your gorgeous plants from delicious to gross and should keep Japanese beetles from eating them. You can also use baby powder sprinkled directly on your plants.
    • As an added benefit the cayenne pepper as it makes the leaves taste spicy and will burn the mouths of squirrels and rabbits that may also feast on your plants.

Nematodes

  • Japanese Beetle life cycleNematodes can help in the two-pronged attack of Japanese beetle prevention. Applying nematodes in the spring and fall when they live in your soil as grubs can kill the problem before they emerge as adult beetles.
  • Consult the life cycle chart for timing or visit the Iowa State University website for some good life cycle information.
  • Only the nematode heterorhabditis bacteriophora is effective in Japanese beetle grub control. This is not to be confused with other types of nematodes (yes they are like dogs with many different species) so getting the right one is key as nematodes are reared for attacking specific grubs or pests.

Old Fashioned Hand Plucking

  • Often the least preferred method for busy people, people with a huge infestation or those in search of a quick fix.
  • When Japanese beetle first appear in your garden removing them by hand when they appear is often a great preventative measure. Where there is one today, there will so be more so preventing them from settling in can help in your battle.

Extremely Measures – Malathion

  • In response to the lack of options left available to gardeners in Ontario, Malathion was returned to the market.
  • This chemical option has shown to give some control on beetles, including Japanese Beetle.

Prevention

  • While Japanese beetles are known to feed on many plant species avoiding their favourites can help keep them away. If you have major problems with Japanese beetles or have a serious phobia, avoid plants like roses, Japanese maple, raspberries and cannas.
  • We have compiled a list of some plants you can use that are less attractive to Japanese beetles, which you can find in our Garden Guides section.

Geraniums to Fight Japanese Beetle?

New research out of Ohio State University shows that geraniums have toxic affects on Japanese beetle. Local gardener Marsha D. brought this to our attention after she decided to do some research when she noticed a large number of dead beetles under her geraniums. Could be some promising developments there. Read the full story.