U. S. Germ v. Jap Beetle

For 25 years the U.S. has tried many a purely defensive measure against Japanese beetles, but last week its first large-scale offensive with hope of success was under way. The offensive was made possible by a newly developed weapon, the Bacillus papillae, which kills grubs under the soil before they turn into the brown-winged green beetles which every summer ravage the Atlantic seaboard from Chesapeake Bay to Long Island Sound.

The Japanese beetle probably came from Japan on a shipment of ornamental shrubs. It was discovered in the U.S. in 1916 near Riverton, N.J. Like concentric ripples in a pool, the beetles spread year by year to surrounding territory. Since quantities of U.S. nursery stock are grown in the most beetled area of New Jersey, the insects would soon have infested the whole U.S. but for a firm Federal quarantine. Each year on the eastern seaboard the beetles now devour millions of dollars' worth of foliage, fruits, flowers, vegetables. They spend over three-fourths of their year of life as grubs, damaging lawns, links and pastures by eating grass roots.

At first U.S. entomologists knew nothing about the insect. The beetle is not troublesome in Japan because 1) scarcely a rood of Japanese soil is left untilled for its grubs to flourish in, 2) natural enemies check its increase. So Japanese scientists were able to offer only one fact--that the beetles were attracted to light--and that proved unreliable.

On the defensive, U.S. entomologists worked on sprays, powders and quarantine methods to check the beetle's sweep. But they looked for a better weapon in the beetle's natural parasitic enemies. Strangely enough they found the most promising of these enemies not in Japan but the U.S.--a germ which hitherto had probably lived on native U.S. grubs. Spreading naturally, it would perhaps become a widespread beetle enemy in 50 years.

By artificial propagation the Department of Agriculture now hopes to spread it ten times as fast. At the U.S. Beetle Control Station at Moorestown, N.J., technicians infect healthy grubs with it, pampering them until the bacteria multiply profusely. Then they grind up the diseased grubs and mix them with talc so the hardy bacteria spores can be conveniently handled and sprinkled in fields.

The most intensive disease-spreading was under way last week in Maryland, where it is subsidized with State funds and helped by the U.S. Department of Agriculture. This week a similar campaign begins in New Jersey, where the first few spores were sown in 1939. The method is to heavily infect two half-acre plots of turf (where grubs thrive best) in each square mile. Birds, breezes and flying beetles then complete spreading the disease. Purpose of spore-sowing is not, as in spraying, to kill beetles on a specific plot but to establish the beetle enemy widely. Spore powder is not available to ordinary gardeners, because the Government is using all that is available to secure maximum distribution--although the Government will not make public just how much land it expects to treat this year, its plans call for the inoculation of 1,800 square miles in Maryland alone.

Parasites do not wipe out all the organisms they prey on: the bacterium itself could not survive if it killed all the beetles. But the Government is also colonizing another beetle parasite, the Asiatic wasp, Tiphia, which lays its eggs on beetle grubs. Next the Department of Agriculture expects to attack the beetle with a fungus. In a few years it hopes that the beetle will be only a moderate garden pest, kept well under control by its natural enemies.

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