70 
THE NATIONAL NURSERYMAN 
extent Belgium, have long maintained practically complete pro¬ 
hibition of plant imports from the United States. 
CONDITIONS NECESSITATING THE QUARANTINE 
Foreign Inspection and Certification Service Inadequate. 
With regard to the actual condition of nursery stock and other 
plants hitherto received from foreign countries, it is appreciated 
that the countries which have been most concerned in such ex¬ 
ports to the United States have established inspection and certi¬ 
fication service, which have very greatly reduced the amount of 
infestation on such exported plants. The conditions in this re¬ 
spect, prior to the passage of the Plant Quarantine Act and the 
requirement of inspection and certification on the part of foreign 
countries, and the rigorous holding of these countries up to as 
high standard as possible, were deplorable. Brown tail moth 
nests and gipsy moth egg masses and numerous other insect 
pests in various stages were coming into the United States in 
quantity, and in one season thousands of such brown tail moth 
nests were found in nursery stock, particularly from Holland, 
Belgium, and France. 'The improvement since the establish¬ 
ment of this service, as indicated, has been very great, hut it 
has not by any means eliminated the danger. 
Of these principal export countries Holland has perhaps as 
good an inspection service as any, if not the best. The stat¬ 
us as to freedom from insects and diseases of plant imports 
from Holland probably represents the best work that can be 
expected under existing conditions of inspection and certifica¬ 
tion on the part of the country of export. Notwithstanding 
the supreme effort of the Netherlands Government to afe- 
guard its plant exportations to the United States, a great 
many injurious insects have been found on stock imported 
from that country since August, 1912, when the Federal 
Plant Quarantine Act became effective. During this period 
of six years of enforcement of this act, no less than 148 dif¬ 
ferent species of injurious insects have been collected on nur¬ 
sery stock imported from Holland. Some of these have been 
found in over 1,100 different shipments of plants. Many others 
have been detected hundreds of times. It is true that many of 
these are insects which have already become established in the 
United States, but many others are insects which have not been 
so established and which are new elements of danger to the hor¬ 
ticulture and agriculture of this country. For example, the Eur¬ 
opean tussock moth iNotolophiis antiqiia) has been found in con¬ 
nection with no less than 67 different shipments of plants from 
Holland, representing over 16 different kinds of ornamental 
plants. Similarly, many other injurious leaf-feeding and wood¬ 
boring insects have been collected on from one to many different 
shipments of plants. 
Soil With Potted and Balled Plants A Special Source 
OF Danger. 
The list of 148 different kinds of insects on Holland stock in¬ 
cludes comparatively few of the soil-infesting species, because 
it has not been possible without destruction of the plants to dis¬ 
integrate and make adequate examination of the soil imported 
with balled and potted plants. The danger is probably much 
greater from such insects concealed in the soil than it is from 
the insects which are found on the aerial portion of the plants. 
Dr. T. J. Headlee, New Jersey State Entomologist, reported at 
the hearing conducted by this Department in May, 1918, on the 
subject of this quarantine, that two years before his office had 
made a limited study of the insect fauna in balled plants from 
Europe and a short examination of perhaps two dozen balled 
plants had resulted in their finding of over twenty different 
species of insects in the soil. 
There is risk of entry from foreign countries through the med¬ 
ium of such soil, of a vast number of insects, many of which may 
have no relation to the plants imported, but are possibly import¬ 
ant enemies of field crops, such as clover, alfalfa, and other for¬ 
age crops and the grains. For example, there are more than a 
score of European weevils and root borers known to infest 
clover, alfalfa, and related plants. Several of these have al¬ 
ready been introduced into this country and are now among 
our most serious forage insect pests. Examples of these 
are the alfalfa weevil now invading half a dozen States 
surrounding Utah, its point of introduction, and the clover- 
leaf weevil now widely distributed throughout the United States. 
Of the same nature are many insects which affect common truck 
crops. Several of these have already been introduced with 
plants imported with soil, such as the European mole cricket, the 
European earwig, and various wireworms. The list of such Eur- 
oiiean truck crop insects possible of introduction with soil is a 
very long one. 'There are also many important European fruit 
insects which can be introduced with soil about the roots of nur¬ 
sery stock. These include apple, pear, and plum weevils, fruit 
and bud weevils, twig and stem borers, and various leaf-feeding 
insects which hibernate in the soil. 
With respect to plant material which it is necessary to bring 
in with soil, it should be borne in mind also that no system of ef¬ 
fective disinfection of the soil about such plants without destroy¬ 
ing the plants is known. 
Plant Pests of Oriental Countries. 
The risk from importations from Oriental countries and other 
quarters of the world where the insect enemies and diseases of 
plants have been very meagerly studied, is illustrated by the es¬ 
tablishment in this country from such sources of many of our 
most important injurious insect pests and plant diseases. Few 
of these were known prior to their appearance In this country, 
and therefore could not specifically have been looked out for 
and guarded against. 
Introduced Oriental Insects. 
Among insects introduced from the Orient are the San .Jose 
scale, the citrus white fly, the oriental peach moth, and the 
Japanese beetle. The peach moth and the Japanese beetle, 
furthermore, illustrate insects which it is apparently impos¬ 
sible to kill by any practicable fumigation in their hibernating 
condition. 
The list of insects introduced from such little-explored coun¬ 
tries is already very large, and the new pests constantly being 
intercepted on plant stock now coming in represent a constant 
and very serious menace to this country. A recent illustration 
of this state of affairs came in last month’s report of Mr. E. M. 
Ehrhorn, a collaborator of the Board and Chief of the Division of 
Plant Inspection of the Board of Commissioners of Agriculture 
and Forestry of Hawaii. Mr. Ehrhorn states that in December, 
1918, he made a thorough examination of two small pots of 
a dwarf Chinese arborvitae {Thuya orientalis) offered for en¬ 
try at Honolulu, and took from the soil about the roots of these 
plants no less than 122 grubs of a curculionid beetle, a near rela¬ 
tive of such injurious insects as the alfalfa weevil, plum and ap¬ 
ple curculio, etc. 
Introduced Plant Diseases 
The danger of introducing plant diseases is just as great if 
not greater than that of introducing new insect pests, and with 
respect to such diseases inspection is a safeguard of no import¬ 
ance. Very often these diseases are not discoverable by inspec¬ 
tion or may develop to a visible stage only after a period o'f 
months or years after the plants have been imported. Notable 
examples of such diseases received from the Orient are the chest¬ 
nut blight and citrus canker from Japan and China. Regarding 
the risk of introduction of dangerous diseases from Europe it ’s 
significant that of the three serious forest diseases that have 
been imported into this country in recent years two of them, the 
white pine blister rust and the European poplar canker, have 
come from Europe, where both these diseases are well known, 
and in spite of the protection of the European inspection service. 
Manuals of Foreign Insects and Plant Diseases. 
A manual describing the dangerous insects likely to be intro¬ 
duced into the United States has recently been published by the 
Department of Agriculture. It was designed for the information 
of Federal and State inspectors, and enumerates and describes 
over three thousand distinct insect pests. Probably half of these 
are Old World insects injurious to forest and shade trees, and 
the balance insects injurious to fruit and ornamental trees and 
to the various farm and garden crops. A similar manual is in 
preparation on the fungous diseases of plants likely to be intro¬ 
duced into the United States. 
Losses Caused by' Introduced Pests. 
In this discussion the actual losses now being suffered from 
plant enemies, insect and disease, which have been introduced 
from foreign sources have not been considered. 'These losses to 
agriculture in this country have been carefully worked out by ex¬ 
perts to cover both the actual damage of these pests to the crops 
concerned, and also the cost of the control operations. This is 
not the place for an extended discussion, but a few illustrations 
may be given. 
Examples of Insects Imported yvitii Plants. 
Typical examples of insect pests introduced with nursery 
stock or other plant material are the San Jose scale, the ori¬ 
ental peach moth, and the Japanese beetle. The San Jose scale 
has been in this country for certainly forty and perhaps fifty 
years. It became widespread throughout the United States in 
the late 90’s, and at the present time there is practically not a 
commercial deciduous orchard in the United States that it is not 
necessary to spray at least once annually to control this pest. 
The expenditures for apparatus and spraying alone in the United 
States amount to approximately $10,000,000 annually. In addi¬ 
tion to this are the losses which the insect causes in spite of this 
