Coping with Rose Chafers

Standard
20160702A

Rose chafer

The American rose chafer* (Macrodactylus subspinosus) is slender pale green to tan beetle with long orange legs. Although it is native to North America, its distribution is fairly irregular: you may have a major problem with it while a neighbor just down the road has never even seen it. It can be found anywhere east of the Rockies.

*The European rose chafer or green rose chafer (Cetonia aurata), metallic green in color, is a different species and is not found in North America.
20160702C

Rose chafers on a rose flower.

Where it is present, the rose chafer can cause a lot of damage, devouring the leaves and flowers of roses. It may eat flowers entirely, while it can skeletonize foliage, leaving only the veins. Moreover, in spite of its name, the rose chafer is far from limited to roses, and will readily consume many other plants, including ivies, Japanese lilacs, hydrangeas, mountain ashes, Boston ivy, daisies, grapes, spireas, elderberries, peonies (flowers), brambles, cabbages, strawberries, apples, hollyhocks, cinquefoils, irises, elms, oaks, birches and hawthorns.

Stop Gap Measures

It is pretty much impossible to entirely eliminate  chafers while the adults are already feeding on your plants, which will be in from late May to mid-July in most regions. The best you can expect is to reduce their numbers to the point where they cause little damage.

Probably the easiest way of controlling the adults is to knock them off the plant into a pail of soapy water or to suck them up with a handheld vacuum (then dump the prisoners into soapy water). For best results, do this in the morning when they are less active.

There are also traps designed specifically for rose chafers that give off a pheromone that attracts them. I have never seen these traps in stores, but you can obtain them from organic insect control specialists, like Nic Natural Insect Control. It is important to place these traps at least 30 feet (9 m) away from any plants the adults like to feed on, perhaps in the middle of a vast lawn or in a parking lot, because while they readily attract chafers into the vicinity of the trap, only a minority of them actually enter it. Then any chafers not caught will damage nearby plants that suit their diet.

Long-term Control

For long-term control, you have to work on either reducing the chafer’s egg-laying ability or on reducing the number of larvae.

20160702D.jpg

Rose chafers prefer to lay their eggs in lawns on sandy soil.

Rose chafers prefer to lay their eggs in sandy soil, preferably in dry, sunny spots covered in grass or weeds, especially lawns. They lay less abundantly in lawns that contain a significant proportion of clover. They dislike and will usually avoid rich, moist soils and shady spots.

To discourage them, you might want to redo your lawn by covering it with a good 6 inches (15 cm) of quality sand-free topsoil, then resowing with a mixture of lawn grasses and clover. Or grow a clover lawn. You can also try planting shrubs, trees, and tall perennials to shade the soil. Obviously, it would help if all your neighbors did the same, as the adults do fly, although they rarely travel far.

20160702B.jpg

Rose chafer grubs look much like other white grubs.

The larval stage of the beetle is a white C-shaped grub that lives in the soil. It is hard to distinguish from the grubs of Japanese beetles or May beetles (June beetles), which also live in lawns under much the same conditions. Nematodes designed to control white grubs will help control all types of white grub, including those of the rose chafer. Beneficial nematodes are readily available in most garden centers or can be ordered from various organic insect control specialists.

There is only one generation of rose chafer per year. After 3 to 6 weeks of damage, the infestation will end as suddenly as it began. Usually affected plants quickly recuperate, producing new leaves, and soon you can no longer see the damage. However, by then the chafers may have already ruined that summer’s blooms or fruit.

Curiously, rose chafers are said to be toxic to chickens, so you might want to keep your hens locked up when they are present!

No Host Plants, No Problem!

The most laidback way to control rose chafer? Every year, eliminate the 3 or 4 plants most seriously attacked, replacing them with species that are not affected (you’ll see which ones in your garden). In just a few years, your yard will no longer offer rose chafers anything interesting and they’ll go elsewhere!20160702A

 

Love Trap for Bugs

Standard
20150720A

Japanese beetle trap.

A pheromone trap is an insect trap that gives off pheromones (chemical substances similar to hormones) used to attract the insect being controlled. Pheromones can mimic the smell of an insect’s favorite food (fruit, flower, etc.), but more often the pheromones used in traps are a bit more libidinous than that: they imitate insect sex pheromones, normally that of the female pest. Thus, the males travel from afar, attracted by the smell of what they think is an attractive young virgin. Once they enter the trap, though, the males can’t get out and therefore can’t impregnate any females, leading to, at least in theory, a drop in the local insect population.

To make the trap even more effective, it is usually colored yellow, blue, green, or purple, depending on the favorite color of the insect.

A Trap for Each Pest

Pheromone traps are very specific: each is designed to attract a particular type of pest. There is therefore no danger they will trap beneficial insects. You therefore have to purchase a different trap for each insect you’re trying to control.

20150720B

Japanese beetle.

The possibilities for pheromone traps are almost limitless, but for the moment, only one is widely available in most areas in North America: the Japanese beetle trap. It is, of course, designed to repress Japanese beetles (Popillia japonica). It actually contains two pheromones: a sex pheromone that mimics the smell of the female Japanese beetle, which therefore attracts male beetles, and another that gives off a floral scent that attracts both sexes.

20150720C

Rose chafer.

Because of the floral pheromone, the Japanese beetle trap can also be used to catch rose chafers (Macrodactylus subspinosus), a Japanese beetle relative. However, there is also a specific trap for rose chafers that only gives off the floral scent. It seems to be more difficult to find in local stores.

Also on the market are apple maggot traps, usually shaped like a red ball that resembles a mature apple. Some models include contain a pheromone: a fruit essence that attracts the apple maggot (Rhagoletis pomonella).

20150720D

Trap for emerald ash beetles.

While the home gardener has only a limited choice of traps, farmers and foresters have access to a wide range of pheromone traps for just as wide a range of crop pests. You may, for example notice, traps placed in ash trees (Fraxinus spp.) In a park in your municipality. With this trap, authorities try to determine whether the dreaded emerald ash borer (Agrilus planipennis) is lurking in the area.

The Downside of Pheromone Traps

20150720E

When the trap is too full, the insects can’t enter.

But there is one major flaw with pheromone traps. While they do indeed attract insect pests to the area, but the latter don’t all enter the trap! Sometimes they simply miss the trap because the scent is carried elsewhere by the wind. Or the trap may already  be full.

Whatever the reason, the result is that pheromone traps often actually don’t reduce insect damage. The insects that didn’t enter the trap, now starving, flock to the nearest available food plant and start to chow down. This is sadly the situation with Japanese beetle traps: they do catch beetles and lots of them, but they also draw more beetles into the sector, so instead of the damage being reduced, it is often worse.

The joke usually proffered is to buy traps and offer them to your neighbors so the beetles will go to their garden instead of yours! That really would work, but I suspect your neighbours would be a bit upset when they find out!

Effective Use of a Japanese Beetle Trap

You can however use the trap effectively if you follow three simple rules:

  1. Place Japanese beetle traps well away from the plants they eat (at least 50 feet/15 m). For example, on a pole in the middle of a lawn.
  2. Empty the traps regularly. Sometimes you have do it every day, otherwise they fill up and new insects can’t get in. Just dump the pests into a bucket of soapy water.
  3. 20150720FCollect beetles daily from nearby vegetation, preferably early in the morning when they are not very active, using a hand vacuum (empty the vacuum afterwards over a bucket of soapy water). Children, especially, seem to find collecting beetles with a vacuum a lot of fun.

If you start using this combined method of insect control at the beginning of the season, you can make serious inroads into reducing the infestation.