GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 19 



has been used in German forests for many years. It has to be applied 

 with a special gun in a thick narrow band encircling the tree trunk. 

 At the present time it is not manufactured in this country, but infor- 

 mation concerning its preparation and use can be supplied by the 

 Greenfield, Mass., office of the Bureau of Entomology and Plant 

 Quarantine. 



SPRAYING 



The most effective spray material is lead arsenate. To make it 

 adhere firmly to the foliage 4 fluid ounces of fish oil or raw linseed oil 

 should be placed in the spray tank for each pound of lead arsenate. 

 The oil should be added after the poison is well mixed with water in the 

 tank, and while the whole is being agitated. Agitation should be con- 

 tinued while the spray is being applied. The best grade of fish oil, 

 known as "light pressed," should be used. Five pounds of lead 

 arsenate to each 100 gallons of spray is required to kill larvae that are 

 half grown. A slight reduction in dosage may be made for the smaller 

 larvae. In areas where there is mixed growth it is impractical to 

 begin the spraying until the trees that produce foliage the latest- — and 

 they are usually the oaks — are ready for treatment. Under such 

 circumstances larvae are found in several stages of development, and 

 use of the stronger dosage may obviate the necessity of respraying. 

 Many investigations are being carried on to develop low-priced non- 

 arsenical insecticides which will not be harmful to man or domestic 

 animals. Improvements along this line would be most useful for 

 gypsy moth spraying operations. 



Warning. — Lead arsenate is a stomach poison and is toxic to animal 

 life. It is unsafe to allow animals to graze underneath trees that have 

 been recently sprayed. When fish oil is used as an adhesive, the 

 spray will disfigure paint on buildings or vehicles unless it is removed 

 with clear water before it has an opportunity to dry. Water may be 

 provided by a low-pressure pump or from a hydrant. Fruit trees 

 should not be sprayed with lead arsenate after the fruit is half grown, 

 as it is difficult to remove the residue. 



CLEAN-UP AND THINNING WORK 



In many areas satisfactory control work cannot be attempted with- 

 out the removal, and usually the burning, of infested rubbish and 

 worthless trees. This should be done in such a way as to improve the 

 property. Woodland areas may be thinned to advantage by removing 

 trees that are favored as food by the gypsy moth caterpillars and 

 encouraging the growth of better species of the less favored classes. 

 When it is necessary to remove dead or useless wood in trees, the best 

 practice of pruning and tree care should be employed. 



EQUIPMENT 



In creosoting work a brush with a round handle, which can be fitted 

 with a cork stopper into a can containing creosote, is useful for treating 

 egg clusters within easy reach. Those higher up can be treated with 

 brushes that are attached at an angle to the tip of bamboo poles ranging 

 from 8 to 18 feet in length. Axes, saws, and bark knives for marking 

 trees are also necessary. 



