INSECTS AND DISEASES WHICH INJURE TREES 



In the first place, there is no single remedy for all insect pests. 

 Avoid as unreliable advice recommending "cure-alls." 



Many insects cannot be exterminated by spraying, but years of 

 study and experiment have resulted in remarkable advances in 

 methods of control. 



Distinguish injury by insects from damage by diseases. Bor- 

 deaux mixture, frequently recommended for any injury or 

 damage to trees, does not kill insects; jt only prevents and con- 

 trols damage by disease. Chewing insects are generally con- 

 trolled by poisoning what they feed on, while sucking insects 

 are only controlled by spraying the insects themselves. 



Must Understand Feeding Habits of Insects. 



Before using any material for the control of insect pests, deter- 

 mine how the creature secures its food (1) whether by chewing 

 and swallowing portions of its food, or (2) by sucking the juices 

 of plants through a tiny beak inserted in the plant tissues. 



The first group, usually called chewing insects, can generally 

 be controlled by poisoning their food at an advantageous time 

 with some of the well-known arsenical compounds. The work of 

 chewing insects is usually recognized by the .ragged or per- 

 forated condition of the foliage which is attacked. 



The second group, composed of sucking insects, can be con- 

 trolled by oily or corrosive contact sprays applied directly to 

 the bodies of the insects. It is useless to attempt any control 

 of a sucking insect by the application of a stomach poison 

 either to the surface or in the sap of a food plant. The work 

 of sucking insects is not so easily recognized as that of the pre- 

 ceding group since the affected plants show little external injury. 

 Gradual weakening, wilting or shriveling of the attacked plant 

 is generally evidence of attack by sucking insects. 



Most Satisfactory Commercial Preparations. 



Insects that suck the juices from plants, foliage, etc., such as 

 lice, green, black and white aphis or fly, mealy bug, red spider 

 and scale, thrust their proboscis into the leaf or stem, and are 

 not affected by stomach poisons ; so they must be destroyed by 

 contact insecticides. Those in powder form kill by closing the 

 breathing pores in the insects skin; or in fluid form by being 

 absorbed through these pores. The best contact insecticides in 

 nowder form are hellebore, slug shot and tobacco dust. The best 

 in fluid form are aphine, black leaf 40, fish (whale) oil soap, 

 nicotine (tobacco extract), kerosene miscible oil and lemon oil. 



Insects that eat plants, foliage, vegetables, fruits, flowers, etc., 

 whether bugs, beetles, worms, caterpillars or slugs, are more 

 quickly and effectually destroyed with a poisonous stomachic 

 insecticide such as arsenate of lead, Paris green or hellebore. 

 These, if applied according to directions, are so diluted as to 

 be harmless to vegetation and to animal life. Less poisonous 

 stomachic and contact insecticides are kerosene emulsion, slug 

 shot, etc. 



Common Arsenical Sprays lor Chewing Insects. 



Paris Green is still a satisfactory insecticide if its foliage- 

 burning qualities are overcome with the addition of a small 

 amount of lime. Arsenate of lead is a more satisfactory mate- 

 rial, which seems to meet most of the requirements for an 

 arsenical poison that will not injure foliage, has good adhesive 

 qualities and, if in the powdered form, will not deteriorate by 

 drying or freezing. The powdered arsenate of lead is therefore 

 recommended over the paste form, which consists of 50 per cent 

 of water and adds to the cost of transportation. 



Arsenate of Lead. Arsenate of lead, although an arsenic com- 

 pound, is a less powerful poison than Paris green and must 

 therefore be used in larger quantities. It is lower, however, in 

 price than Paris green. Arsenate of lead may be obtained in 

 two forms, viz., a thick, white paste or a very fine powder. The 

 powdered form, although not differing chemically from the paste, 

 has advantages over the paste form since it is not injured by 

 freezing or drying. The paste arsenate of lead is one-half water 

 and for this reason twice as much of the paste as of the powder 

 must be used in the usual spraying operations. 



The powdered form is coming into general favor and use for 

 dry applications by means of dusting apparatus. The rapidity 

 and ease of application and the good results secured are tending 

 toward a widespread use of this form of the poison. 



Arsenate of lead has advantages over Paris green in adhesive 

 quality, non-burning of foliage, and the white color by means 

 of which thorough spraying is more easily determined. Arsenate 

 of lead remains in suspension in water longer than Paris green, 

 which settles to the bottom more quickly. 



ARSENATE OF LEAD-PROPORTIONS FOR SPRAYING. 



Arsenate of lead (powder) 1-J lbs. 



Water, Bordeaux mixture or lime-sulphur solution SO gals. 



or 



Arsenate of lead (paste) 3-6 lbs. 



Water, Bordeaux mixture or lime-sulphur solution SO gals. 



In small quantities use, 



Arsenate of lead (powder) . . 1 tablespoonf ul 



Water 1 gallon 



Paris Green. This well-known spray material is an arsenical 

 compound which when pure is a brilliant green, finely divided 

 powder. 



It may be applied in a liquid spray or may be used with ten 

 or twelve times its weight of plaster Paris, flour, or fine air- 

 slaked lime which is preferable. 



Burning of the foliage when spraying with Paris green will 

 occur on account of a small amount of water soluble arsenic. 

 This difficulty may be overcome by using an equal amount of 

 lime which counteracts the burning qualities. Paris green has 

 only one advantage over arsenate of lead on account of its more 

 violent poison and its quicker action on insects. 



The use of Paris green for spraying is advantageous in case 

 the poison needs to be removed where plants are used for show 

 purposes. The same is true in its use on certain fruits which are 

 approaching the ripening stage. 



PARIS GREEN PROPORTIONS FOR SPRAYING. 



Paris green 5-J oz. 



Lump lime 1 lb. 



Water or Bordeaux mixture (never lime-sulphur) 50 gals. 



In small quantities use, 



Paris green 1 teaspoonful 



Lump lime Size of a walnut 



Water 2 gals. 



Hellebore. This vegetable poison, which is manufactured by 

 finely grinding the roots of the white hellebore plant, has been 

 used quite generally on trees and shrubs bearing fruits which 

 are nearly ripened and almost ready for picking. Hellebore 

 quickly loses its poisonous properties on exposure to the air and 

 sun; and it will lose its strength rapidly unless it is kept in 

 air-tight containers. 



Poison Bran Mash. A mixture of Paris green, bran, syrup 



