The Japanese Beetle

CONSIDERING that the Japanese beetle is Japanese, it may seem surprising that in the United States it occurs exclusively in the East. It came from Japan the long way, probably in soil attached to some imported plants, straight to one of our Eastern ports. There is, naturally, no record of its unauthorized entry; all that is known is that it first showed up in Riverton, New Jersey, in 1916. From then on, it has never stopped. Although in Japan it is not particularly common, it found our Middle Atlantic seaboard tremendously to its liking, and within a few years it had multiplied to prodigious numbers. which it still maintains, so that it must seem strange to anyone from, say, Philadelphia, that in most of the country people have never seen the insect.

The heart of the Japanese-beetle country is around Philadelphia and the corner where Pennsylvania, Delaware, and Maryland meet; it also extends through New Jersey, and includes small corners of New York and Connecticut, an area of about 26,600 square miles.

The Japanese-beetle season is from the middle of June to the latter part of August, or somewhat earlier in the southern part of its range and later in the north. Throughout July the beetles swarm in gardens, in orchards, in truck farms, and everywhere in nature. They eat a tremendous variety of plants, — more than 260, according to counts, — but among these they have decided preferences. Of grapevines and rosebushes they will often eat every single leaf down to a skeleton of veins; in apple, cherry, and peach orchards they will swarm on to each fruit so that you cannot see the fruit, but only a bunch of beetles. They are very partial to corn, of which they eat the silks projecting from the ears, so that the pollenization is imperfect and the ears develop very few grains, or none at all. Fortunately there are some plants that are seldom or never attacked by them. They do not like a number of garden plants and ornamental shrubs; they leave us some useful vegetables, such as cabbages, carrots, potatoes, tomatoes, onions, squash, and turnips; they do not trouble the small grain farmers, and they do not eat evergreens, with the exception of cypress.

They are very pretty little beetles, and would be likable if only there were not so many of them: nearly half an inch long, with the prevailing color a fine metallic green, though the wing covers, which form most of the back, are a pleasing copper color. They are gregarious — where you find one beetle you will usually find at least twenty — and they have a habit of sticking their back legs up while they are on a leaf. It is a pity they are so numerous that they can become a nuisance merely by flying into the windshields of cars.

From September onwards they begin to disappear, except for a few stragglers, to everyone’s intense relief. But they continue their destructive work unseen, and in a different form. Each female beetle has laid from forty to sixty eggs, placing them in the ground a few inches deep, and these have hatched into white grubs, the larvæ which will turn into the beetles of next summer. These white grubs feed upon the roots of plants, particularly grass. They hibernate in the soil during the winter, but next spring they resume activities, feeding upon roots again, after which they spend about a month in the inactive pupal state. Then they emerge as adult beetles, to start the cycle all over again. These white grubs in the soil can be as numerous as twenty, fifty, or even a hundred per square foot. That number of root eaters makes a difference, and the result is nasty bare patches in lawns and gardens, and in the fairways and greens of golf courses. Thus the Japanese beetle is working against us even when we cannot ordinarily see him. One way or another, his depredations set us back an estimated $2,739,000 a year.

What can be done about it?

There are two things we can do. The first is to do something ourselves; the second is to wait while the Department of Agriculture does something. The second course has very much to recommend it.

You can shake the beetles off by hand. You get up early in the morning, when the bugs are not so lively, put a sheet under the plant, — preferably a shrub or a small tree, — and shake like mad. Then you empty the sheet into a bucket half full of water with some kerosene in it. Farmer’s Bulletin No. 1856 of the Department of Agriculture points out that ‘this practice does not, however, prevent reinfestation from outside sources’ — which means it is very discouraging work.

You can spray against them, taking your choice from a variety of spray materials. Some of them have a liquid poison that will kill all beetles that are hit by it, though it will not prevent other beetles from coming along later. Others have a solid poison, and work differently; few Japanese beetles will actually be killed, for they are not as some stupid insects that will munch avidly of a poisoned leaf until they drop — they do not like the taste or perhaps the feel of the poison, and rather than eat it at all they will fly away and eat somewhere else. This, of course, is exactly what you want: you have saved your garden at the expense of painting it whitish. Indeed a spray of lime and alum, not poisonous at all, will do this trick, and there are special chemicals nowadays that are exceptionally distasteful to the Japanese beetle, and do a fine job of repelling it. They repel it, true; but since they do not kill it, and there is plenty of food for it elsewhere among the 260 varieties of plants it eats, there will always be plenty of beetles for next year, and you are faced with the prospect of doing this every year for the rest of your life.

You can poison your lawn against the grubs. An arsenical poison is simply spread over the grass, and then washed in by watering thoroughly with the hose. This is not practicable for pasture land, and is very expensive for large areas, but on a lawn or a golf course it will give protection for five years.

You can trap the beetles, buying from commercial firms traps of a design carefully worked out by the Department of Agriculture. The flying beetles are attracted by a special mixture of aromatic-smelling chemicals, and the gadget is cunningly arranged so that they bump against a baffle plate and then fall into a quart jar from winch they cannot get out. Cynical persons declare that the only good Japanese beetle trap is one in your neighbor’s garden, whither more beetles are attracted by the smell of the chemicals than actually go into the trap. But the solution is to have a trap in your own garden and one in your neighbor’s garden too — in fact a trap in everybody’s garden, by a community effort. At the height of the season you can empty the quart jar every day and find it full, and if everybody is doing this, with one trap or more, formidable quantities of beetles wall be destroyed. This sort of community effort is particularly popular among farmers in Maryland; in the summer of 1940 they caught in this way 275 tons of beetles.

What is the Department of Agriculture doing about the Japanese beetle?

The answer to this is ‘plenty.’ You will probably never notice the Department’s men at work, and they do not fight the insect with chemical sprays, which you must apply yourself if you want this kind of protection. They have other, more subtle, means of attack, the development of which goes back a long way.

When it became apparent that the pretty little green and copper aliens were going to be a Pest in a Big Way, the entomologists of the Department of Agriculture reasoned as follows: The beetle is not abundant in Japan; why not? It must have enemies there, probably insect enemies, that control it and keep it within reasonable bounds. So, beginning in 1920, entomologists were sent to Japan and other parts of the Far East to look for these valuable parasites and send them to the United States. This is a regular method of attack against introduced insect pests, and has been used against many of our worst insects.

Three little flies and two small wasps have settled here and are living their plan of life, according to which their immature stages, or larvæ, feed exclusively upon either the larvae or the adults of the Japanese beetle. It is the three flies that are having difficulties. For instance, one of them lays its eggs upon an adult Japanese beetle; the eggs hatch into tiny worms that work their way into the body of the beetle and feed on it from the inside; the beetle is killed and the fly larvae turn into pupae which pass the winter, and from which flies emerge the following summer. Now in Japan the flies emerge just at the same time that the beetles are emerging, and so they easily find beetles on which to lay their eggs; but in this country a slight difference in the climate causes them to emerge somewhat earlier, when very few adult Japanese beetles are available: consequently they are able to get only the early beetles. The other two flies are also upset, in similar ways, by subtle differences in the climate.

The two wasps both have the generic name of Tiphia: they are the Spring or Korean Tiphia, and the Fall or Japanese Tiphia. The female wasp burrows into the soil in search of a Japanese-beetle grub; when she finds one she stings it, which paralyzes it for about half an hour, and attaches an egg to its belly. Then she goes off to find another grub. The egg hatches, and the wasp larva remains attached to the grub, sucking its juices until the grub is totally consumed. The two Tiphias are very similar, but they do their work in the spring or fall, as their name indicates. They have been introduced in hundreds of different places in the Japanesebeetle country, and, as they spread very slowly from place to place, this work is still going on. It is not expected that they will be the final answer to the Japanese beetle, but they may very appreciably reduce its alumdance, and this kind of work, once completed, will never have to be done again.

However, the best weapon against the Japanese beetle is a bacillus. Insects suffer from diseases just as we do, and, since few of us have strong humanitarian feelings with regard to insects, we do not scruple to bring about outbreaks of disease among them. The Japanese beetle is one of the few insects against which this can be done with success, and its ‘Type A milky disease,’ caused by a bacillus, is being propagated with great energy by the Federal Government, with several of the states coöperating.

The centre for this work is the Department of Agriculture Experiment Station at Moorestown, New Jersey. There about a million grubs each year are inoculated with the disease and then ‘incubated,’ under suitable conditions, until each one becomes a mass of the minute spores of the bacillus. They are then dried and ground to a powder, which is diluted with powdered talc to a standard concentration of forty-five billion spores per pound. This lethal mixture is applied to the soil in the Japanese-beetle country, on a square-mile basis, treating from one to six acres in each square mile, according to the severity of the infestation.

The disease is slow in starting; it may take a year or more to get going; but it then causes a terrible mortality among the injurious grubs. It is also slow in spreading by natural agencies, but this is taken care of by the work of the scientists at Moorestown, who hope in two years to have at least one centre of infection in every square mile of Japanesebeetle territory. It has also a virtue corresponding to its slowness; the spores will last in the ground for four years even if no Japanese-beetle grubs are there at first, and so it can be applied in advance in places just outside the present range of the beetles, to be ready for them when they get there.

If you are a sufferer from this pest take heart: there will be a centre of ‘Type A milky disease’ in the same square mile as your garden within two years at the most, and if you are in the worst-infested part there is probably such a centre within a mile of you now. The Federal entomologists do not promise eradication, but this is not necessary; if the beetles undergo a considerable reduction in numbers, they will be no worse than many another pest that has always been with us. Twenty years have elapsed with no relief from the annual July nuisance; now there is a prospect of an abatement of the plague with no more effort on our part than that of waiting for the Moorestown men to come round with their bacillus. This should be good news for Japanese-beetle haters.