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Weekly Gardening Guide: Those Little Buggers!

July 9, 2015

It will soon be "that time" of year again. You know what I'm talking about... Japanese Beetle season! In fact, I hate to say it, but I’m pretty sure I’ve seen a few flying around already. I'm sure every gardener has fought this pesky pest at some point in their gardening life. Here's a little bit of info about the beetle, and how to control or reduce the devastation it can cause to your beautiful gardens if left unchecked:
Popillia japonica, or Japanese Beetles are an invasive pest which was introduced to North America in the early 1900’s, and is thought to have come over from Japan on a shipment of iris bulbs before inspections of shipping containers became strictly regulated.
They feed on the a wide number of ornamental landscape plants, especially trees and shrubs, notably roses, Japanese Maples, Birch, Linden and more. They are aggressive defoliators, and if left untreated can eventually kill a tree by way of removing significant portions of its photosynthetic tissue (though this is only in extreme cases). In most cases, they are just an “aesthetic nuisance”.
They are right on cue this year, as the adults will typically fly from mid July until late August, during which period they will mate and lay dozens of eggs each - usually in the surrounding lawn or other grassy areas. As I’m sure many of you are probably already aware, Japanese Beetle larvae (recently hatched eggs) are one of the “white grub” species which attack our home lawns.
So in other words, these bugs are real BUGGERS from birth until death!
Fortunately, there are some helpful control strategies that you can put into place to help control the damage caused by these Green menaces:
- First, start by populating your garden with species which are non, or less susceptible to beetle attack. Some notable examples include: all Holly varieties, All euonymous, boxwood, lilac, yew, most spruce and most hydrangeas.
- In fact, some plants actually REPEL Japanese Beetles, and its a great idea to plant these nearby or interspersed within your garden. Examples are: Garlic, Chives, Onions, Marigold and White Geranium.
- Reducing adult feeding starts with reducing viable larvae! Kill those grubs by applying nematodes or Milky Spore during spring and fall while grubs are actively feeding on lawn roots! These are both biological controls which work by inoculating your soil with living organisms that specifically attack white grubs (and only white grubs).
- When you do find them feeding on your plants, you can spray the beetles with a Pyrethrin-based product such as End All or Bug-X. This is a naturally derived product harvested from the pyretrhin daisy which kills the beetles on contact.
- After you've killed them, chemically or otherwise, it has been shown that leaving the dead beetles in the garden can actually deter or repel new beetles from coming to the area. I caution you though, they do stink!

I would like to discuss traps at length now, as they are always in high demand this time of year and they are always a polarizing topic among gardeners. Traps attract beetles with a combination of a potent floral pheromone, and a mating pheromone. The idea is that no matter what “mood” the beetle is, it will still prefer to fly towards your trap over a less potent smelling plant. The beetle attempts to land on the slippery inner surface of the trap, where they lose their footing and slide into the reservoir. Beetles need room to take off horizontally, and cannot fly straight up so they can’t get out of the small space, and they eventually die.

Do they work? Yes, if by “work” you mean attract and trap beetles by the hundreds! However, they don’t just attract your beetles, they also attract your neighbour’s, and your neighbour’s neighbours’ (I really struggled with punctuating that one, if my old English teacher is reading this – I hope I did you proud). So, here is what I recommend when it comes to traps: Strength in numbers! If you live in a neighbourhood where the lawns and gardens are well tended by loving homeowners, approach a few of your neighbours and ask if they would be willing to put traps in their gardens as well! If you knew you had a few traps scattered throughout your neighbourhood, then you wouldn’t be getting any higher numbers of beetles than your neighbours and you would hopefully be able to reduce the amount of feeding and more importantly – the number of eggs they will lay for the next generation!

However if you do not live in a “gardening neighbourhood”, and think you may be fighting a losing battle, traps may not be for you. Putting one trap in the middle of a block of unkempt gardens may just make it the hottest club in town for the hard partying beetles. But they may not even make it to the club before they get hungry and want to stop for a bite to eat at the Linden café, or even try to pick up a cute girl on your pine tree… (this analogy could go south real quick, so lets move back to the literal side of things). The beetles may *smell* the trap nearby but that doesn’t mean they’ll go straight to it, so they may still lay eggs in your lawn, feed on your ornamentals or mate in the trees!

If you have a large property, you could consider sacrificing one area up wind of your primary gardens where you could set the trap and plant a few fragrant desirable plants as named above. This technique is used in farming and is called “trap stripping”, where several rows of more desirable plants will be planted amongst the cash crop to draw insects out of the cash crop and into the trap rows. Then the farmer will just treat the trap strip with pesticide or other control in an effort to lower the pest population without spraying his entire field! This same technique could translate into a large garden with the use of “trap plants” and actual traps!

As you’ll note, all of the above techniques could be combined into an “Integrated” approach to managing this pest. If you’re a loyal blog reader, you will recall my recent post about IPM (if not, you can find it on this page). This is truly the most effective way to reduce these pests!

993 words, under 1000!

As always please feel free to contact us with any questions or concerns about this or any other gardening topic!

Happy Gardening!


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