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A fuller description of the various lines and methods of work which are supplementary to the principal methods of creosoting and burlapping will be discussed under the head of "Cleaning Work."

The presence of the burlaps on the trees in Providence occasioned not a little variety of conjectures as to their purpose and use. In spite of the fact that explanations were given in a bulletin issued during the summer and distributed through the entire infested district, and also by newspaper articles, a great many supposed that the bands of burlap had been treated with a poisonous substance which in some more or less mysterious way should kill the caterpillars when they came in contact with it. Others thought that the burlaps were designed as barriers to prevent the ascent of the caterpillars, and were very much chagrined, and probably commented on what they took to be a foolish procedure, when they noticed that the caterpillars sought refuge under the bands and had but very little trouble in passing over them to the foliage above. Many thought that they would improve upon the method used by the State and tacked the burlap bands to the trees, or painted them with tar, whitewash, or oil paints, all of which, as anyone who understands their use will realize, defeated the real purpose for which they were put on.

The burlapping work is essential, and in spite of the fact that a large share of the expense of an exterminative policy comes from the use of the burlaps, nevertheless, their efficiency, as already intimated, is such that it is essential to use them.

SPRAYING.

This method of combating, so common in the treatment of many other injurious leaf-eating insects, is of secondary importance in dealing with the gypsy moth because of its rather peculiar ability to resist the action of poisons. Experiments in the Massachusetts work have shown that a gypsy moth caterpillar can eat a quantity of poison which would usually destroy several caterpillars of other insects. Chemical analyses have shown that a gypsy moth caterpillar may

[graphic][merged small]

Photograph showing method of wrapping a strip of burlap around a tree

and cutting it off with a knife.

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have a quantity of poison in his system sufficient to destroy any other insect and still be in good health and complete its metamorphosis. It has even been found that poison remains in the system of the insect while it passes through the pupa and into the imago form. Nevertheless, if spraying is used while the caterpillars are young, it will serve to materially check their numbers. Even at this time it is necessary to use a quantity of poison which is much in excess of that ordinarily employed, and the operation is therefore quite expensive. The plan of work this summer has been to use spraying only where there was danger of the trees being defoliated by the caterpillars, or where it was necessary to destroy as many as possible before they could be scattered to other sections. This was especially true where they were found around places where carriages and wagons were stored for short periods, or where street cars passed under or came in contact with the foliage of infested trees.

When spraying was first begun, ten pounds of lead arsenate were used per hundred gallons of water. This quantity was increased, as the caterpillars grew larger, until about fifteen pounds were used when the caterpillars were half-grown. It may be said in passing that lead arsenate was first used as an insecticide in the first Massachusetts campaign against the gypsy moth, and has been found to be the best spray remedy for the pest. No other poison can be applied to the trees in sufficient quantities to destroy the caterpillars without injuring the foliage to a considerable extent. Paris green, for instance, if applied of sufficient strength to destroy the gypsy moth caterpillars, would seriously burn the foliage of most of our shade and fruit. trees, even with the addition of a quantity of slaked lime.

Certain rules and principles are kept in mind in the application of insecticides; one is, that the spray must be applied in a very fine mist-like form. This is accomplished by using a good, up-to-date Vermorel nozzle and a pump through which a sufficient pressure can be secured to thoroughly break up the spray as it passes through the orifice. It is essential that this pressure amount to from 75 to 125 pounds per square inch.

Many ask questions as to whether the spraying of trees is no

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to poison the fruit, if they are fruit trees, or to deposit sufficien the poisonous substance on the foliage and on the grass underne to be injurious to animals which may happen to eat of the foliage or grass, or even to fall off and poison people who may happen to be under the trees. A little reasoning will satisfy anyone that there is no danger to people from the distribution of the poison from the foliage. There is also no danger from poisoning by fruit which has been sprayed, unless possibly when the spraying has been done s1. -y before the fruit is ripe and ready to use. There have been a great many experiments made to determine whether there is enough of poison on the grass underneath sprayed trees to be injurious to cattle. One of the most convincing of these is mentioned in the report of the Massachusetts State Board of Agriculture in which a dairyman purchased the hay from an orchard which was sprayed several times during the season and fed it to his cattle. No injurious effects whatever resulted.

It is desirable to avoid spraying fruit trees while in blossom because it is liable to prevent the proper fertilization of the flowers, and ecause it is injurious to the bees which may visit the trees at this time.

BANDING WITH STICKY SUBSTANCES, ETC.

In some cases where trees have been cleared of insect pests and it is desired to protect them from re-infestation by caterpillars migrating from neighboring infested trees, banding of the trees with some sticky material which will act as a barrier is successfully practiced. This is also efficient in protecting trees from certain insects, notably the canker worms, which pupate in the ground, and the wingless females of which have to reach the foliage of the trees by climbing to deposit their eggs. It should be noted, however, that much of the banding which one notices on trees throughout the country is a waste of ti and money because no insects are present against which the remed is useful, and because the method is such that it would be inefficient in any case.

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