Among the various sources of nitrogen fertilizers, possible deposits of nitrates in the arid and semiarid areas of the country have long held a prominent place in the scientific and popular mind. Our people have observed and studied some deposits of this character. Generally, however, these deposits are either too small in amount to justify commercial exploitation or they are inaccessible to transportation or available water for working them, or are otherwise of doubtful economic importance. There is no available experience in this country to guide our people in working such deposits, the conditions surrounding them being essentially different from those in other countries.

Whether or not natural deposits of nitrates can be commercially exploited is yet an open question, but it is a distinct advance to know that such deposits exist. Various other sources of nitrogenous fertilizers have also been investigated, and it is especially worth noting that there is a well-defined tendency in our main coking regions to introduce modern ovens and make available large quantities of ammonia, which have generally been discarded until very recently.

Especial interest attaches to the work on potash fertilizers, because commercial sources of potash have been unknown in this country, the world's supply in fact coming from the Stassfurt deposits in Germany. The advantage of having a domestic source is so obvious as to require no comment. Possible sources of potash are by no means few. Much potash can be recovered from the immense accumulations of sawdust in our lumbering regions, from the vinasses in our sugar mills, from wool washings, etc. Possible sources of potash include also the bitterns or mother liquors from our salt workings. These are now under investigation. Segregated deposits of potash salts may lie under our known salt deposits, or below the present surface in desiccated sea or lake beds. This is now being investigated. The desert basins are being explored by our agents for surface deposits of potash, as well as nitrates.

The utilization of natural potash-bearing silicates has long attracted investigators and inventors. Vast deposits of potash feldspars, glauconite, leucite, and other suitable minerals exist in this country, and our laboratories as well as private parties are now actively at work on methods for extracting the potash. The extraction of potash in various ways is perfectly feasible in the laboratory. But the energy required to break down the chemical combinations. and extract the potassium is so large as to make its production inhibitive at the present time. Extremely cheap power or the incidental production of valuable by-products might possibly make the potash silicates commercially available.

There is, however, one mineral which occurs in large quantities and which offers some hope of becoming a commercial source of potash. This is the basic alumino-potassic sulphate known as alunite. From it potash alum (known commercially as Roman alum) has long been made in Europe. Our people have shown that potash can be readily obtained from the mineral, and, by special devices which they are studying, probably other by-products can be obtained which will greatly cheapen the cost of the potash.

The most promising source of potash at present is found in the large areas of kelp groves or sea algæ lying along the Pacific coast, growing wherever there is a rocky bottom and a rapid tideway, or beyond the surf line, at depths of from 6 to 10 fathoms. These groves are of various areas from beds of a fraction of an acre to stretches 5 miles in length and 2 or more miles in width. During the past summer our people have mapped about 100 square miles of kelp groves in different localities from Puget Sound to Point Loma and have studied the character of the algae as well as the conditions necessary to their utilization commercially and to their maintenance as a permanent resource of the country. Many more areas yet remain to be studied and mapped, but from what has been accomplished in this preliminary work I am assured that a conservative estimate shows that the kelp which could be gathered from the 100 square miles already surveyed, and without detriment to the permanence of the groves, should yield 1,000,000 tons of chloride of potash annually, worth at least $35,000,000, or about thrice the value of the present importations of potash salts from Germany.

Satisfactory methods of gathering the kelp are yet to be worked out, but present only minor mechanical difficulties. The value of the kelp is, moreover, probably much greater than represented by the content of potash alone. Our laboratories have shown that iodine and other useful products can be obtained which will pay in large measure, if not fully, for the cost of gathering the kelp and abstracting the potash salts.

Enough has been accomplished to show that this country has within its own borders resources to meet the fertilizer requirements of the present, and for a greatly increased use in the coming years. The saving to our people which can reasonably be expected from these investigations is enormously greater than the cost. These investigations are, however, but little more than begun, although begun very well. That they should be liberally supported and actively prosecuted can admit of no possible argument. Economic independence of outside nations with large financial gain to the public at the same time is a desideratum justifying the utmost effort of our scientific investigators and strong sympathy and aid from the people's representatives.

BUREAU OF ENTOMOLOGY.

The work of the Bureau of Entomology covers the whole field of the economic aspect of the work of insects, whether they are injurious to agriculture or horticulture or to domestic animals or man, or whether they are beneficial in one way or another. Only a few of the numerous investigations carried on under this bureau can be mentioned here.

WORK ON THE GIPSY MOTH AND THE BROWN-TAIL MOTH.

The general conditions in that portion of the country originally invaded by the gipsy moth, that is to say, eastern Massachusetts, have been better during the past year than for many previous years. This has been due in part to weather conditions, to the prevalence of the wilt disease, to the gradual increase of parasites imported from abroad, and to the cumulative effect of the excellent work done along roadsides by the Bureau of Entomology, in certain forests by the State of Massachusetts, and in the different towns under municipal and State control. The conditions in New Hampshire, however, are much worse than in Massachusetts. Many towns in the southeastern part of the State are seriously infested, and the insect occurs in 125 towns in all. In several of the northern towns the pest has apparently been exterminated. In Maine there has been a further spread, and a new colony has been found in Rhode Island. The brown-tail moth has established itself in the northeastern part of Connecticut.

The increase and spread of the imported parasites and natural enemies of both the gipsy moth and the brown-tail moth has been gratifying, and several species have been brought in during the past year in large numbers which the Bureau of Entomology had not previously been able to secure. During the summer an imported Japanese egg parasite, which had previously been thought to have died out, was recovered in considerable numbers. An appreciable effect upon the numbers of the gipsy moth as the result of parasitic work is beginning to be noticed.

New studies have been begun of the feeding habits of the newly hatched caterpillars of the gipsy moth, and already it seems that it will probably be possible to control the gipsy moth in forested areas by a certain variation in forest management dependent upon the feeding habits of the young caterpillars. This means that the forests of New England, and later other portions of the country, are not doomed, and that a good stand of timber can be maintained even should the pest increase beyond the ultimate control of the parasites, and this in itself is most unlikely. It appears, in fact, that the number of species of forest trees upon which the young

gipsy moth larvæ can feed and maintain themselves until they reach a considerable size is very limited.

THE ALFALFA WEEVIL.

The situation regarding the alfalfa weevil, an insect obviously imported from Europe, and which became established in the vicinity of Salt Lake City, Utah, is continuing to become more serious and alarming. The last Congress made immediately available $10,000 for an investigation of the pest. Experts of the Bureau of Entomology, working in cooperation with the Utah Agricultural Experiment Station, have traced the spread of the insect from Salt Lake City south to Springville and north to Ogden, west to beyond Tooele and east to Wyoming. Judging from what has been observed between Salt Lake City and Ogden, and between Ogden and Brigham, the uniform normal spread of the pest is about 30 miles a year, though circumstances may greatly change this. Many experiments have been carried out with mechanical devices for destroying the pest in infested alfalfa fields and thereby protecting the second and third crops. An investigation was made of the parasites of this weevil in Italy, and during March and April last large lots of the stems of alfalfa containing eggs parasitized by a minute parasite were sent to Salt Lake City, arriving there in good condition and the parasites emerging in numbers. Three other parasites were sent over later, and an attempt is now being made by agents of the bureau to establish them in the Utah alfalfa fields.

WORK IN THE ORANGE AND LEMON GROVES OF CALIFORNIA AND FLORIDA.

In my last report I mentioned the completion of the study of the problem of hydrocyanic-acid gas fumigation in California, directed against certain scale insects on citrus trees, and stated that the careful experimental work carried on had resulted in a great reduction in the cost of fumigating, since one treatment under the new methods was as lasting in its effects as three or four distinct treatments under old commercial methods. Observations during the past year have shown that this was an underestimate, and that an orchard once fumigated will remain clean for three years before it is necessary to repeat the operation. Thus the cost of keeping an orchard free from scale is now only one-sixth of what it used to be in the days of commercial and unscientific treatment.

The work in Florida against the white fly having demonstrated that in most cases the gas treatment is too expensive, attention has been directed to the determination of the most practical and effective spray application. Tests have been made on a large scale, often over entire orchards, with a variety of insecticides, and it now seems

rather well demonstrated that spraying will, under Florida conditions, be more generally adopted in the future than control by fumigation. The expert who was sent abroad in a search for the original home of the white fly, and with the idea of importing from this locality, when found, parasites or natural enemies which could be established in the Florida orange groves, has been successful in at least a part of his mission. In November, 1910, he found the white fly at Seharunpur, India, under conditions that appear to indicate that the white fly is indigenous to that part of the world. He has found that it is attacked by two species of ladybird beetles, and he has also found an internal parasite. A large part of the present year has been devoted to the effort to secure the parasites in sufficient numbers and in proper condition to permit sending them successfully to this country. He has established the white fly on small growing trees, and has secured living specimens of the parasite breeding in these white flies, and the trees themselves will be brought to the United States in Wardian cases.

The investigation of the orange thrips, begun at Lindsay, Cal., has been extended to southern California, especially in the Riverside district, where it seems to be causing considerable damage. Application of a spray consisting of a lime-sulphur solution with a tobacco extract added is the best remedy so far found.

WORK AGAINST FOREST INSECTS.

It is significant of the practical nature of the methods of barkbeetle control recommended by the Bureau of Entomology and of the practical demonstrations that have been carried on that no complaints of depredations have come to the bureau during the year from the areas in Colorado and Montana where control work was carried on in previous years according to the instructions of the bureau. During the past year the work has been principally in the way of practical demonstrations, as the result of the investigations of previous years. As an example, in cooperation with private owners in the vicinity of Columbia Falls, Mont., over 10,000 trees were treated. Formerly 10,000 trees died each year, but as the result of last year's work only 2,000 required treatment this year within an area of more than 100 square miles. This is undoubtedly the direct result of the control work of last year, which cost nothing, since the treated trees when utilized for fuel and lumber are worth far more than the cost of treatment. Work done in cooperation with the Interior Department on the Glacier National Park resulted in the treatment of 1,295 trees in the vicinity of McDonald Lake, and the present conditions indicate that the work has been successful in arresting the spread of the damage.

23165°-AGB 1911-8