INSECT PESTS 351 



has it the almost velvety appearance. It happens not unfrequently that a tree may be in- 

 fested by both pests, for insects often seem to prefer plants that are not in very robust 

 health to those that are. The leaf-curl fungus attacks Peaches, Nectarines, and Almonds. 

 How it gains access to the tissues of its host is not at present very certain, but it probably 

 does so through the leaves. Having once established itself in a tree, there is no means of 

 eradicating it except by cutting off the parts infested by it. The fungus lives throughout 

 the year in the shoots and smaller branches, pushing its growth into the young leaves as 

 they are opening, which causes a very abnormal growth of their tissues. The cells in the 

 parts of the leaves between the veins growing much more rapidly than the veins, causes the 

 leaves to become crumpled. These portions of the leaves are also much thicker than the 

 other, and eventually the diseased parts become covered with a delicate bloom, the result 

 of the spore-bearing part of the fungus being pushed through the surface of the leaf so 

 that the spores can escape. The little spore-bearing cases are technically known as 

 " asci," and cover the surface of the diseased part of the leaf. Each ascus or case con- 

 tains at first only eight spores, but these increase by budding until the case is full. When 

 ripe the spores are liberated and are carried about by the air, infecting any leaves they 

 may meet with. 



As to the best way of dealing with this pest, probably the most useful is to cut off any 

 shoot that bears infected leaves as far back as possible, so as, if possible, to remove all 

 the infected wood and burn it. Any leaves which are diseased that may have fallen 

 should be gathered up and burnt. Spraying with Bordeaux mixture as the leaves are 

 opening, and again in about three weeks' time, is useful in destroying any spores that may 

 be carried from other trees. There is no method by which the fungus while in the shoots 

 of the tree can be destroyed, so that when once a tree is infected, unless the diseased por- 

 tions can be cut off, the fungus is almost sure in time to kill the tree. A certain amount of 

 shelter to the trees in inclement weather as the leaves are opening, so as to prevent any 

 checking of their growth taking place, is most useful, and should always be provided if 

 possible. Though such precautions may appear to prevent an attack, it should always be 

 borne in mind that they do not kill the pest, but merely prevent it from growing into the 

 leaves and bearing fruit, just as some plants will not flower in seasons that are not con- 

 genial to them, for the pest remains in the shoot or shoots all the same. The number of 



INSECTICIDES 



is so great that it is impossible to even enumerate all of them, but many if not 

 most of them are quite useless, so a few have been selected whose value is generally 

 recognised. It should always be remembered that one application is seldom suffi- 

 cient, for as a rule the eggs, if there are any, are not killed, so the process should be 

 repeated in the course of five or six days, and care should be taken that the undersides of 

 the leaves are properly wetted when they are infested by red spider, thrips, and other pests 

 that live in that position. Most insecticides are best applied by a spraying machine or a 

 syringe with a spraying nozzle. These are made so that the under sides of the leaves are 

 easily reached, and much less of the insecticide is needed than if an ordinary syringe is 

 used. Soft soap forms one of the ingredients in most of the mixtures. The reason of this 

 is that the soap helps the fluid to adhere to the insects and it also chokes up their breath- 

 ing pores. (Insects do not breathe through their mouths but through certain pores which 

 are usually placed on either side of their bodies.) Insecticides should not be used when 

 the sun is shining on the plants or in very bright weather. Apply them in the evening and 

 wash the plant clean the next morning. Plants with very tender shoots and foliage are 

 more likely to be injured than others, and in their case the washes should be more diluted. 



Paraffin Emulsion, composed as it is of two ingredients, both very fatal to insects, is one 

 of the best. It should be made by dissolving one quart of soft soap in two quarts of boil- 

 ing water, and stirring in while the mixture is quite hot one pint of paraffin oil. To make 

 the combination of the oil and soap more complete it should be worked through a syringe 

 for some five or ten minutes until a creamy mixture is formed. If this has been properly 

 done the oil and the soap will not separate. If they do the oil floats on the top, and it is 

 difficult to insure that some part of the plant does not get a stronger dose of it than it 

 should and so be injured. To every pint of this emulsion add ten pints of water before 

 using it. 



Mr. H. H. Cousins, of the Agricultural College, Wye, recommends a mixture very 

 similar to the above, but with a certain amount of naphthaline added to it. Directions 

 for making it can be obtained from him ; or it can be bought under the name of 

 " Paranaph." 



Tobacco Water. Boil i oz. of strong tobacco in a gallon of water, add 2 oz. of soft 

 soap, strain and use when cold. It should then be of the colour of fairly strong tea. 



