One given in the American Gardener’s almanac is that between the months of June and August, a flurry in concern about Japanese beetles descends with them across the country. With their metallic shells, these rose loving pests are yet to let up, even with pest control measures in place from countless gardeners, farmers and horticulturists generally. Although they are one of the rarer pests, on the whole, the adult is a truly devastating insect. It has been known to defoliate a tree in a matter of days.
What Plants Do Japanese Beetles Attack?
As adults, they can feed on around 400 species of plants that grow within our gardens. These include ornamental shrubs like roses and a sizeable variety of trees. They also present something of a double whammy in that they feast on different plants as both grubs and beetles.
A Quick Rule of Thumb
In case you’re short on time and need the golden rule straight away, note that the softer the plant’s flesh, the greatest risk. This unfortunately includes fruits and vegetables as the greatest casualties. The leaves preferred by the Japanese beetle include those with softer foliage, especially fruits and flowers which are more delicate to the touch and which they work on in the flesh between the veins. For the sake of illustration, the most notable victims are roses and hibiscuses and fruits like grapes and raspberries. Vegetables most at risk are soy and maize. Those which will usually survive the brunt of Japanese beetles include the likes of Magnolia (with its tough leaves and flowers) red oaks, pines and red maples, and of course Holly, as well as fruits with a fairly tough skin.
One Interesting exception
Geraniums, while loved by the Japanese beetle contain a compound that paralyzes them for around half-an-hour and is quite often used as a trap plant by more eco-conscious gardeners who will then collect them one by one and bag them before they are able to wreak any more havoc.
Japanese Beetles spend 8 months of the year as grubs feasting on lawns’ roots. The wetter the grass, the larger the infestation is liable to be.
Although the roots of other plants are not completely immune, it’s the roots of lawns that suffer most during this stage. You’ll know this is the case by a quite severe case of die-back in your lawn which often so severs that it exposes the top-soil. The positive side of finding the insect in your lawn at this point is that you can take the opportunity to stop them in their tracks before they develop tougher jaws and mandibles capable of working through your trees’ leaves.
One of the best solutions for curbing further growth is to grab a bag of fertilizer that says “Grub Control” on the label and apply it over the resulting bare patches of grass.
Alternatively, buy a bag of fertilizer that supports nematode growth. It’s these microscopic little creatures’ whose job it is to eat grubs. This is definitely the most environmentally friendly solution as well.
With their small wings, they are not strong fliers, but Japanese Beetles tend to prefer feasting on foliage that grows in sunny areas of the garden. This includes the foliage of mature trees, although larger trees will be able to withstand an invasion of the insects without much long term damage.
The beetles will not touch pine trees and are less apt to attack yews, spruces, or forsythia. At this stage, they tend to seek out softer-leaved maples, oaks (like the tender pin oak), and fruit trees, along with vegetables that range from green beans to soybeans.
One way to swing this to your advantage is to place a pheromone trap at the border of your smallholding or garden. Especially if you can find a suitable trap that doesn’t sabotage other beneficial bugs, this is a great and easy way to check a mass infestation.
For an in-depth List
For a more exhaustive list of the best and worst-faring plants in the midst of a Japanese beetle infestation, you can visit the website for the USDA. If you’re unsure, the tell-tale signs of an invasion of neighboring plants in your area are the best guide.
Other Notable Exceptions
Plants in which pungent garlic or onion aroma are usually immune to attack. This is also true of pines.
Farmers have also known for a long time now that some cultivars of fruits are hardier against attack than others, so it’s worth choosing your blackberry variety (for example) more carefully next time you pay a visit to your nursery, especially if Japanese beetles pose a threat in your area.
Here is a further list of vulnerable and less vulnerable plants Japanese beetles attack for the sake of illustration. It should be noted that these beetles will attack even some of the hardier plants on the list for lack of better options though. Click here for more information.
Plants Do Japanese Beetles Attack
- Peaches, Apricots, and plums
- Crab apples
- Crape myrtle
- Japanese maple
- American linden
- Pin oak
- Norway maple
- Buckthorn shrubs
Plants Least Likely to be Attacked
- Burning Bush
- Northern red oak
- Red maple
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